Consumer Sleep Technologies (CST’s)
– Dr Tripat Deep Singh

Sleep has been recognized by professional medical bodies as essential to health.1 It is recommended that adults should sleep 7-9hrs in the night.2 We are becoming a sleep deprived society.3,4 Chronic sleep deprivation has been associated with daytime sleepiness5, hypertension6, diabetes mellitus7, all-cause mortality8, increased driving accidents9, decreased female fertility10, decreased sperm count11 and negative influence on work performance.12 Also, there are >84 types of sleep disorders listed in International classification of Sleep disorders.13

We as individuals need to take charge of our Sleep as sleep is essential to health and sleep deprivation causes various disease states. Recent studies have shown that people are sacrificing Sleep for sedentary activities14 and pushing back their sleep time for spending more time on smart phones for catching up on social media.15 This has been shown to increase the risk for cardiovascular disease.16

The most accurate way to measure Sleep is Polysomnography (PSG). It’s a technique where a lot of sensors are placed on the patient to record different physiological parameters during the night. It is a whole night procedure where a person needs to sleep for one whole night in the sleep lab. A trained physician or sleep technologist analyses the whole night data next morning to generate a sleep report which tells about persons sleep, respiration, heart activity and body movements. One need to measure following during PSG- electroencephalography (brain activity), electrooculogram (eye movements) and electromyography (muscle activity) to record sleep of the person.

PSG is a very labor-intensive procedure, not readily available, require highly trained manpower, is expensive and time consuming. It is not a good way to measure sleep at population level over multiple nights due to these disadvantages. We need simple technologies that can record sleep for several nights in patients own sleeping environment enabling people to take charge of their sleep and get involved in the management of their overall health.

Ownership of smart phones have increased and a lot of technologies have leveraged this to monitor sleep through apps, gadgets connected to smart phones or through stand-alone devices. This has brought the monitoring of sleep from sleep lab to consumer level.

Consumer sleep technologies (CST’s) refer to computer-based systems available to general public for improving or self-monitoring their sleep. CST’s are not medical grade devices. Their primary goals have been described as Sleep induction, Wake induction, Self-guided sleep assessment, Entertainment, Social connection, Information sharing and Sleep education.

There are five primary delivery platforms for CST’s17

  1. Mobile device Platform
  2. Wearable platform
  3. Embedded platforms
  4. Desktop or website platforms
  5. Accessory appliance platforms
CST  DescriptionExamplesAdvantagesDisadvantages
Mobile device Platform  This consists of mobile apps running on smart phones and tablets. They do not require external sensors except for smart phone or tabletSleep cycle Sleep Bot Sleep as android Sunriser Entrain Go! To Sleep  Convenient and easy to use   App accessibility   Device capability and flexibility  Sleep disruption from noise and light pollution   Reduced processing power compared to stand-alone devices   Smart phone need to be placed on the bed. Sensor accuracy may suffer due to other people lying on the same bed.  
Wearable platforms  A sensor is placed directly on the body or attached or embedded in clothing. Track body movement or biometric information  Fitbit Jawbone UP (Discontinued) Smart watches Basis peak Mimo baby monitor Sleep Image GarminIncreased accuracy with direct contact with wearerDiscomfort Limited battery life Device misplacement Sensor damage Inaccuracy from frequent use
Embedded platformsNon wearable devices embedded in users sleep environmentTanita sleep scan Sleep number x12 Luna Beddit Dozee  Unobtrusiveness  May raise privacy concerns due to easy concealment
Desktop or website platformsComputer programs or websites designed to run on a full desktop operating systemMedhelp sleep tracker Myapnea.org Somryst (SHUTi) Sleepio SleepyHeadIncreased processing power   Larger data storage   Better exchange of information  Higher cost   Decreased portability   Large platform variability
Accessory appliance platformsAny physically separate device that may or may not interface with mobile devices or internetClocky Philips wake up light emWave Resmed S+ Sense with sleep pill Withings Aura Earlysense liveFeature design flexibility   Improved functionalityIncreased cost of stand-alone device   Diminished space economy

Table 1: Summary of different CST platforms

Ideally any CST should monitor and report at least the following parameters about sleep-

  1. Amount of NREM Sleep and its substages- Stage N1, Stage N2 and Stage N3 (Deep Sleep)
  2. Amount of REM Sleep
  3. Total sleep time
  4. Sleep onset latency- It means how long one took to fall asleep after lying down in bed
  5. Stage REM latency- it means time after sleep onset when first stage REM occurred
  6. Time at which patient went to bed
  7. Time at which patient wake up
  8. Time in bed
  9. Sleep efficiency
  10. Wake after sleep onset (WASO)- It refers to time for which patient was awake after sleep onset

But not all currently available CST’s report above parameters. Most of the CST’s report sleep as light sleep, deep sleep and REM sleep rather than telling about specific NREM substages.18 The definition of deep sleep also vary between different manufacturers and it does not always mean Stage N3 of NREM sleep.18

CST should also be able to tell about sleep quality quantitatively19 and predict over all sleep health score20 for consumers to understand about the influence of their overnight sleep on their health. Very few CST report qualitative sleep quality and none report on Sleep health score for meaningful interpretations of overnight sleep data.

Another important parameter to be reported is chronotype of the person. Chronotype means at what time of the day one is most active. Different individuals differ in the time of their peak alertness. Chronotype is of three types-

  1. Morning type- These people are maximally active during morning time and tend to sleep early
  2. Evening type- These people are most active in the evening and tend to sleep late
  3. Neither type

It is very important to understand one’s chronotype to sleep at the right time. An evening chronotype person will find it difficult to sleep between 9-10pm which is usual recommended sleeping time for adults to get 7-9hrs of sleep. I am not aware of a single app that combines chronotype information with above sleep information to provide meaningful interpretation and suggestions for overnight sleep.

CST’s versus PSG

Most of the CST’s use accelerometry to detect body movements and do sleep staging based on this data rather than recording electroencephalography (brain activity), electrooculogram (eye movements) and electromyography (muscle activity) to record sleep of the person like in PSG. When patient is moving device marks it as wakefulness and when lying still the device marks it as sleep. The algorithm to predict light sleep, deep and rem sleep are proprietary and manufacturers do not disclose them to clinicians and researchers which makes it very difficult to do comparative studies comparing different CST’s.

Accelerometry is also used by medical grade technology to record sleep and wakefulness called Actigraphy. Actigraphy is considered mobile sleep assessment standard. It’s a small watch like device worn on non-dominant wrist and reports total sleep time, time in bed, wake after sleep onset, sleep onset latency, sleep efficiency, light intensity and mid-point of sleep. Actigraphy allows for multi night recording of sleep in patients own sleeping environment and is extensively used to record sleep at population level in research studies. But actigraphy overestimates sleep time and underestimation of wakefulness when compared to PSG.

Very few manufacturers provide validation of the sleep data reported by their devices by comparing their device data with PSG or actigraphy. While choosing CST to track your sleep, I will recommend to look for CST’s which report validation of their sleep data against PSG or actigraphy.

A recent study compared seven consumer sleep tracking devices against PSG and Actigraphy in healthy adults.21 They tested four wearable devices (fatigue science readiband, fitbit alta HR, garmin Fenix vivosmart and garmin vivosmart 3) and three non-wearable devices (earlysense live, resmed S+ and sleepscore max) against PSG and Actigraphy. They reported that all these devices except Garmin performed better than actigraphy in detecting sleep vs wake and they tended to perform worse on nights with disturbed or poor sleep.21 We need more studies like this comparing other CST’s with PSG or Actigraphy.

Another study reported on validation of three phone apps (Sleep time, MotionX 24/7, Sleep Cycle) against PSG.22 None of the three apps correlated with PSG and failed to accurately reflect sleep stages.

A recent study reported that only 32.9% of sleep apps contained information supporting their claims, 15.8% included clinical input and 13.2% contained links to sleep literature. Also, apps contained information on how sleep is affected by alcohol or drugs (23.7%), food, daily activities and stress (13.2%). Users gave high rating to apps that contained a sleep tip function.23

One of the issues with validating CST’s data against PSG or Actigraphy is frequent updates of the CST models or their software’s by the manufacturers. By the time a validation study is published, manufacturers either come with a new model with revised algorithms or upgrade the software of the existing devices which makes it impossible to apply validation study results to new models or revised algorithms.

CST across different age groups

Validation of data across different age groups is not available and scant available data shows different results across age groups.

In healthy adults Fitbit Charge 2 when compared to gold standard PSG overestimated total sleep time and time spent in N1+N2 sleep stage, underestimated sleep onset latency and stage N3 but did not differ in estimation of time wake after sleep onset and time spent in REM sleep. Fitbit Charge 2 correctly identified 82% of PSG-defined non-REM-REM sleep cycles across the night in healthy adults and also in subjects with PLMS.24

In pediatric population (3-17yr), Fitbit Ultra significantly overestimated Total Sleep Time(TST) (41 min) and Sleep Efficiency (SE) (8%) in Normal mode, and underestimated TST (105 min) and SE (21%) in Sensitive mode.25

In adolescents, Fitbit Charge HR significantly but negligibly overestimated TST by 8min and SE by 1.8%, and underestimated WASO by 5.6min (p<0.05).26

CST’s and disease management

Scientific community is increasingly interested in using CST’s for treatment follow up of different disease states as it provides multiple night data and allows assessment of the effectiveness of the treatment. Current data in different disease states show different results.

Recently a protocol of a study is published studying the clinical applicability of wearable device (Fitbit Charge HR or Fitbit Charge 2) generated data to the management of thyrotoxicosis by analysing continuously monitored data for heart rate, physical activity, and sleep in patients with thyrotoxicosis during their clinical course after treatment.27

In major depressive disorder patients, Fitbit Flex (FBF) in normal setting significantly overestimated sleep time and efficiency, and displayed poor ability to correctly identify wake epochs. In the sensitive setting, the FBF significantly underestimated sleep time and efficiency relative to PSG.28

Some studies have tested the proof of concept that these technologies can be used as diagnostic tools with varying results. A recent study compared data from Polysomnography with snore data recorded from smartphone taped to patients chest and found good agreement between RDI from smart phone and AHI from PSG.29 However in real life settings the recordings may be affected by the presence of a bed partner and other sounds in sleeping environment including bed partner snoring.29

Data from Sonomat, contactless sleep monitoring system embedded into a foam mattress which detects apneas and hypopneas, was found to have good correlation for AHI, apnea index and hypopnea index for AHI<50events/hr when compared to polysomnography (PSG). 30 Sonomat has recently been validated for detecting sleep disordered breathing in children as well.31

Data from another contact-free monitoring system (EarlySense, Ltd., Israel) was compared to PSG.32 It comprised of an under-the-mattress piezoelectric sensor and a smartphone application, to collect vital signs and analyse sleep. Total Sleep Time estimates with the EarlySense were closely correlated with the PSG. This system also showed good sleep staging capability with improved performance over accelerometer-based apps.32 It can also collect additional physiological information on heart rate and respiratory rate.32

Sleep on Cue, i-phone based app, was compared with PSG to detect sleep onset.33 Sleep on Cue app uses behavioural responses to auditory stimuli to detect sleep onset. Sleep on Cue app overestimated sleep onset latency by 3.17min.33 Total Sleep Time and sleep latency estimated by another i-phone app, Sleep cycle, in Children (2-14yr) did not correlate with PSG.34

Most of the available CST’s are validated in healthy population and need validation in patients with sleep disorders. Studies have shown that CST’s perform poorly in patients with sleep disorders or disturbed sleep.21 My advice is that if you are already diagnosed with sleep disorder or suffer from poor sleep, then see a Sleep physician and do not rely too much on the sleep data shown by CST.

These technologies are becoming an integral part of human lives. Whether we like it or not, patients are coming to the clinic asking to interpret the data of these devices. I usually take a look at the data to see whether it is making any sense clinically. I am happy that these technologies are at least engaging the consumers and making them self-aware and interested in their own Sleep health. But there is a danger that these CSTs may prevent few patients from seeking professional evaluation and treatment or even destroy doctor-patient relationship by providing conflicting advice. Also, app users may be exposed more to their smartphones before bedtime which may have influence on circadian rhythms of the person and make sleep onset difficult.

CST and Insomnia management

The first line of management for Insomnia is cognitive behavioral therapy (CBT). It involves 6-8 1hr sessions with trained Psychologist. CBT is not commonly available and there is a try to offer digital CBT for Insomnia to overcome the problem of trained experts.

CST offer a great chance to achieve the delivery of digital CBT for Insomnia. Clinical studies have shown that digital CBT for Insomnia helps to reduce severity of Insomnia symptoms.35,36 another study have shown that use of digital CBT is effective in improving functional health, psychological well-being, and sleep-related quality of life in people reporting insomnia symptoms.37

A number of digital CBT programs have been developed; the 2 most widely known and fully automated programs are Sleepio and Somryst (previously called SHUTi). Both deliver content and exercises across 6 sessions over a flexible timeline, and content remains available to suit the patient’s needs.

Sleepio is delivered via their website and has an accompanying smartphone application; Somryst was historically delivered via their website and is now available via a smartphone application. Both Sleepio and Somryst use dynamic, user-friendly interfaces to keep patients engaged (eg, animations that illustrate treatment content), and both use patient input (eg, sleep diaries and in-program questions) to personalize the intervention. The US Food and Drug Administration recently cleared Somryst as a prescription digital therapeutic (PDT), which can be prescribed much like pharmacological interventions.

Orthosomnia

While CST’s have the potential to engage people in their own Sleep health, it has also led to increased preoccupation or concern regarding perfecting the wearable sleep data. This increased concern in perfecting the wearable sleep data has caused sleep problems in some patients and the condition has been termed Orthosomnia.38

I feel that CST’s have a role to play in monitoring Sleep but we need to educate the society about what CST can and cannot do. We need to be clear that CST’s are one of the ways to monitor your sleep health and any abnormal data coming from these devices should alert the person to seek medical consultation rather than keep trying to perfect the data following wrong practices and aggravate the sleep problem.

Which CST should I use to monitor my Sleep?

This is the most common and difficult question asked by my patients when discussing about CST’s. I tell my patients to choose CST by considering the following points-

  1. First decide what all do they want to measure. Is it sleep only or other things like physical activity as well.
  2. Do they need information on sleep only or other physiological parameters like heart rate, respiratory rate and heart rate variability as well?
  3. Look for validation data against PSG or actigraphy
  4. Check whether data can be shared with the Physician in a meaningful format
  5. Check whether sleep quality is reported and if reported is it quantitatively evaluated
  6. Check whether a Sleep health score along with its interpretation is given. Do they explain how sleep health score was computed?
  7. Check whether sleep tips are included
  8. Check whether the technology takes into consideration the chronotype information while advising on Sleep
  9. Check whether you are looking for CST offering treatment for Insomnia
  10. Check whether the information regarding sleep and solutions for sleep problems are based on scientific literature with appropriate references.
  11. Check whether the CST alerts you to see a Sleep Physician with a list to choose from

I am sure you will be able to choose the right CST for yourself after going through blog and monitor and track your Sleep for timely interventions when required.

Until then, sleep well and on time.

References:

  1. Ramar K, Malhotra RK, Carden KA, et al. Sleep is essential to health: an American Academy of Sleep Medicine position statement. Journal of Clinical Sleep Medicine.0(0):jcsm.9476.

2. Hirshkowitz M, Whiton K, Albert SM, et al. National Sleep Foundation’s sleep time duration recommendations: methodology and results summary. Sleep Health. 2015;1(1):40-43.

3. Effect of short sleep duration on daily activities–United States, 2005-2008. MMWR Morb Mortal Wkly Rep. 2011;60(8):239-242.

4. Kocevska D, Lysen TS, Dotinga A, et al. Sleep characteristics across the lifespan in 1.1 million people from the Netherlands, United Kingdom and United States: a systematic review and meta-analysis. Nat Hum Behav. 2021;5(1):113-122.

5. Punjabi NM, Bandeen-Roche K, Young T. Predictors of objective sleep tendency in the general population. Sleep. 2003;26(6):678-683.

6. Gottlieb DJ, Redline S, Nieto FJ, et al. Association of usual sleep duration with hypertension: the Sleep Heart Health Study. Sleep. 2006;29(8):1009-1014.

7. Luyster FS, Strollo PJ, Jr., Zee PC, Walsh JK, Boards of Directors of the American Academy of Sleep M, the Sleep Research S. Sleep: a health imperative. Sleep. 2012;35(6):727-734.

8. Soh AZ, Chee MWL, Yuan JM, Koh WP. Sleep lengthening in late adulthood signals increased risk of mortality. Sleep. 2018;41(3).

9. Stutts JC, Wilkins JW, Scott Osberg J, Vaughn BV. Driver risk factors for sleep-related crashes. Accid Anal Prev. 2003;35(3):321-331.

10. Wang ID, Liu YL, Peng CK, et al. Non-Apnea Sleep Disorder Increases the Risk of Subsequent Female Infertility-A Nationwide Population-Based Cohort Study. Sleep. 2018;41(1).

11. Chen H-G, Sun B, Chen Y-J, et al. Sleep duration and quality in relation to semen quality in healthy men screened as potential sperm donors. Environment International. 2020;135:105368.

12. Appleton SL, Reynolds AC, Gill TK, Melaku YA, Adams R. Waking to use technology at night, and associations with driving and work outcomes: a screenshot of Australian adults. Sleep. 2020;43(8).

13. Sateia MJ. International classification of sleep disorders-third edition: highlights and modifications. Chest. 2014;146(5):1387-1394.

14. Zomers ML, Hulsegge G, van Oostrom SH, Proper KI, Verschuren WMM, Picavet HSJ. Characterizing Adult Sleep Behavior Over 20 Years-The Population-Based Doetinchem Cohort Study. Sleep. 2017;40(7).

15. Chung SJ, An H, Suh S. What do people do before going to bed? A study of bedtime procrastination using time use surveys. Sleep. 2020;43(4).

16. Matricciani L, Dumuid D, Paquet C, et al. Sleep and cardiometabolic health in children and adults: examining sleep as a component of the 24-h day. Sleep Med. 2021;78:63-74.

17. Ko PR, Kientz JA, Choe EK, Kay M, Landis CA, Watson NF. Consumer Sleep Technologies: A Review of the Landscape. J Clin Sleep Med. 2015;11(12):1455-1461.

18. Ong AA, Gillespie MB. Overview of smartphone applications for sleep analysis. World Journal of Otorhinolaryngology-Head and Neck Surgery. 2016;2(1):45-49.

19. Ohayon M, Wickwire EM, Hirshkowitz M, et al. National Sleep Foundation’s sleep quality recommendations: first report. Sleep Health. 2017;3(1):6-19.

20. Brindle RC, Yu L, Buysse DJ, Hall MH. Empirical derivation of cutoff values for the sleep health metric and its relationship to cardiometabolic morbidity: results from the Midlife in the United States (MIDUS) study. Sleep. 2019;42(9).

21. Chinoy ED, Cuellar JA, Huwa KE, et al. Performance of seven consumer sleep-tracking devices compared with polysomnography. Sleep. 2021;44(5).

22. Choi YK, Demiris G, Lin S-Y, et al. Smartphone Applications to Support Sleep Self-Management: Review and Evaluation. Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine. 2018;14(10):1783-1790.

23. Lee-Tobin PA, Ogeil RP, Savic M, Lubman DI. Rate My Sleep: Examining the Information, Function, and Basis in Empirical Evidence Within Sleep Applications for Mobile Devices. J Clin Sleep Med. 2017;13(11):1349-1354.

24. de Zambotti M, Goldstone A, Claudatos S, Colrain IM, Baker FC. A validation study of Fitbit Charge 2 compared with polysomnography in adults. Chronobiol Int. 2017:1-12.

25. Meltzer LJ, Hiruma LS, Avis K, Montgomery-Downs H, Valentin J. Comparison of a Commercial Accelerometer with Polysomnography and Actigraphy in Children and Adolescents. Sleep. 2015;38(8):1323-1330.

26. de Zambotti M, Baker FC, Willoughby AR, et al. Measures of sleep and cardiac functioning during sleep using a multi-sensory commercially-available wristband in adolescents. Physiol Behav. 2016;158:143-149.

27. Lee JE, Lee DH, Oh TJ, et al. Clinical Feasibility of Continuously Monitored Data for Heart Rate, Physical Activity, and Sleeping by Wearable Activity Trackers in Patients with Thyrotoxicosis: Protocol for a Prospective Longitudinal Observational Study. JMIR research protocols. 2018;7(2):e49.

28. Cook JD, Prairie ML, Plante DT. Utility of the Fitbit Flex to evaluate sleep in major depressive disorder: A comparison against polysomnography and wrist-worn actigraphy. J Affect Disord. 2017;217:299-305.

29. Nakano H, Hirayama K, Sadamitsu Y, et al. Monitoring sound to quantify snoring and sleep apnea severity using a smartphone: proof of concept. J Clin Sleep Med. 2014;10(1):73-78.

30. Norman MB, Middleton S, Erskine O, Middleton PG, Wheatley JR, Sullivan CE. Validation of the Sonomat: a contactless monitoring system used for the diagnosis of sleep disordered breathing. Sleep. 2014;37(9):1477-1487.

31. Norman MB, Pithers SM, Teng AY, Waters KA, Sullivan CE. Validation of the Sonomat Against PSG and Quantitative Measurement of Partial Upper Airway Obstruction in Children With Sleep-Disordered Breathing. Sleep. 2017;40(3).

32. Tal A, Shinar Z, Shaki D, Codish S, Goldbart A. Validation of Contact-Free Sleep Monitoring Device with Comparison to Polysomnography. J Clin Sleep Med. 2017;13(3):517-522.

33. Scott H, Lack L, Lovato N. A pilot study of a novel smartphone application for the estimation of sleep onset. J Sleep Res. 2018;27(1):90-97.

34. Patel P, Kim JY, Brooks LJ. Accuracy of a smartphone application in estimating sleep in children. Sleep Breath. 2017;21(2):505-511.

35. Vedaa Ø, Kallestad H, Scott J, et al. Effects of digital cognitive behavioural therapy for insomnia on insomnia severity: a large-scale randomised controlled trial. Lancet Digit Health. 2020;2(8):e397-e406.

36. Soh HL, Ho RC, Ho CS, Tam WW. Efficacy of digital cognitive behavioural therapy for insomnia: a meta-analysis of randomised controlled trials. Sleep Med. 2020;75:315-325.

37. Espie CA, Emsley R, Kyle SD, et al. Effect of Digital Cognitive Behavioral Therapy for Insomnia on Health, Psychological Well-being, and Sleep-Related Quality of Life: A Randomized Clinical Trial. JAMA Psychiatry. 2019;76(1):21-30.

38. Baron KG, Abbott S, Jao N, Manalo N, Mullen R. Orthosomnia: Are Some Patients Taking the Quantified Self Too Far? J Clin Sleep Med. 2017;13(2):351-354.

Chronic Sleep Deprivation in Adults
– Dr Tripat Deep Singh

Chronic sleep deprivation refers to not getting enough sleep per 24hrs for one or multiple nights. Chronic Sleep deprivation can happen due to1-

· Medical conditions like pain

· Sleep disorders

· Work demands which include extended work hours and shift work

· Social and domestic responsibilities

· Bedtime Procrastination

We are becoming a chronically sleep deprived society due to above reasons without understanding what harm it is doing to our health. Whenever I see a patient with chronic sleep deprivation I make sure that I explain to them how chronic sleep deprivation is damaging their health. In this blog I am summarizing what I tell my patients about harmful effects of chronic sleep deprivation to bring a meaningful change in their Sleep behavior.

What happens if adults chronically restrict night sleep to <7-9hrs?

Chronic sleep deprivation to <7-9hrs of sleep every night affects most of the body systems unlike acute total sleep deprivation which have mainly neurocognitive deficits.

1. Increased Sleep Propensity during daytime

· If sleep is chronically restricted to <6hrs, one feels sleepier during daytime as assessed by Multiple sleep latency test (MSLT) 2

· This increases the risk of road traffic and occupational accidents

2. Sleep architecture may be preserved despite poor cognition

· Amount of Slow wave sleep is preserved even after chronic sleep restriction to 4-7hrs per night3

· Slow wave sleep has been shown to be associated with daytime cognitive functions

· Cognitive functions can deteriorate even when slow wave sleep is preserved if you are chronic sleep restricted to 4-7hrs per night3

· This is very important to understand in today’s world, where gadgets are used to monitor sleep. Do not think that you have normal cognitive function if your gadget is showing normal slow wave sleep while you are chronic sleep restricted to 4-7hrs per night

3. Bad Cardiovascular and metabolic health

· Both men and women with a usual sleep duration of 7 h had the best survival4

· Sleeping <6hrs increases odds for Hypertension5

· Sleeping more and less than 7.7 h/night had an increased BMI4

· Sleep times ≤ 6h or ≥ 9h/night were associated with an increased prevalence of type 2 diabetes and impaired glucose tolerance.

· Persistent short (<5hrs) or long sleep (>9hrs) or increasing sleep duration in late adulthood was associated with increased risk of all- cause mortality, especially from cardiovascular causes6

· Shift workers experience reduced sleep time and circadian disruption which leads to poor cardiovascular health7

· Decrease of N3 and REM sleep with aging increases BMI by 3.3Kg/m2 in males and 4.4Kg/m2 in females.8 This is worrisome as an increase of 1Kg/m2 in BMI increases risk of developing diabetes mellitus by 19% 9and, for persons with BMI more than 25, 6% higher risk of all-cause mortality.10

4. Increased Driving accidents

· Sleeping <6hrs increases road traffic accidents11

· Sleep deprivation leads to worse driving control as compared to driving control under the influence of alcohol. Intake of coffee does not improve driving performance after sleep deprivation12

5. Impaired Cognition

· Restricting sleep to <7hrs per night chronically leads to cumulative deficits in cognitive performance functions

· Cognitive impairment is worse after restricted daytime sleep as compared to restricted night time sleep, which means shift workers suffer more cognitive impairment

· Study have shown that Short sleep duration (<6hrs) might be an early marker of Alzheimer disease.13

6. Altered Endocrine profile in the evening

· Restricting sleep to 4hrs per night for 6nights leads to elevated levels of evening Cortisol, sympathetic activity, decreased thyrotropin levels and decreased glucose tolerance levels14

· Increased Cortisol levels make it difficult to fall asleep and increased sympathetic activity is harmful for cardiovascular health

7. Impaired Immune function

· Studies have shown that sleep or sleep loss influence immune function.15,16

· Shorter sleep duration on the two nights before the vaccination predicted fewer antibodies 1 and 4 months later.17

8. Negative effects on Mind

· Sleep deprived individuals are irritable, impulsive, have more negative emotions, prone to errors and accidents18

· Bedtime procrastination increases risk for depression, anxiety and Insomnia. 19Bedtime procrastination is a habit where individuals push back sleeping time for leisure activities by engaging more on smart phones.

· Sleep deprivation at workplace leads to lower job satisfaction, decreased charisma of others, decreased helping behavior among colleagues and increased hostility20

9. Impaired regulation of appetite

· Sleep deprived individuals have increased ghrelin and decreased Leptin levels which increases appetite

· Increased appetite leads to increased eating which may lead to obesity

10. Altered reproductive health

· Patients with Non-apnea sleep disorders leading to sleep deprivation are at increased risk of developing female infertility21

· Sleep duration of <6hrs or >9hrs is associated with poor sperm health22,23

11. Negative influence on work performance

a. Waking up at night for texting or emailing affects work performance next day

· Waking up at night for texting or emailing leads to chronic sleep deprivation. This leads to next day sleepiness, fatigue, impaired mood, motivation and attention24

· People who wake up for texting or mailing attribute their symptoms to causes other than sleep deprivation24

· They are 6.4 times more likely for drowsy driving related accidents, 4.8 times more likely to miss work and 2.2 times more likely for errors at work24

b. Extended duration work shifts (24-28hrs) in Physicians affects their performance

· Resident physicians obtained less than 4 hr of spontaneous overnight sleep on 92% of extended-duration work shifts, an amount insufficient to prevent serious neurobehavioral performance impairment. 25

c. Sleep restricted (5.6hrs per night sleep) individuals feel groggy on awakening (Sleep Inertia) at night and can commit errors in decisions

· Cognitive performance in sleep-restricted (5.6hrs per night sleep) individuals was worse within 2 min of awakening, remained worse across the dissipation of sleep inertia, was worse during the biological night, and worsened as days of insufficient sleep increased. This have implications for all individuals needing to perform tasks quickly after awakening like Physicians26

How long it takes to recover following chronic sleep restriction?

Studies have shown that if individuals are chronically sleep restricted for 7nights to <5hrs per night, then either two 10hrs or three 8hrs sleep opportunities are required to recover performance to baseline levels.27,28

Effects of sleep restriction on performance can be mitigated by extending sleep prior to sleep restriction.29 This has been referred to as “Banking Sleep” and is one of the recommendations for athletes to maintain their performance prior to any major sporting events.30

At this stage we do not know whether we can reverse all the damage caused by chronic sleep deprivation by extending the sleep time in sleep deprived people. My advice is to change your habits now to avoid further sleep deprivation and more damage to your health.

Common ineffective Strategies to overcome chronic Sleep deprivation in adults with harmful cardiovascular and metabolic effects

When we sleep less than what is required we accumulate “Sleep debt”. People adopt following strategies to pay their sleep debt-

1. Extending sleep duration over the weekends: Due to social or work demands people are sleeping less on weekdays and try to extend their sleep time on weekends.31,32 One can increase sleep time over the weekend in two ways-

a. Later wake up times than weekdays: This has been referred to as catch up sleep at weekends. It has been shown to be associated with increased risk of poor health-related quality of life and anxiety/depression.33

b. Combination of later sleep time and wake time over the weekend: This has been referred to as Social Jet lag. This has been linked with an increased risk of obesity, type 2 diabetes mellitus, and impaired metabolic control in noncommunicable diseases.34-37

2. Naps: Many people try to take naps to overcome sleep deprivation. Naps (<60 or >60min) have been shown to be associated with all-cause mortality and naps >60min duration with cardiovascular disease.38 When people with night time sleep <6hrs took naps (<60 or >60min) it decreased the all-cause mortality but not the incidence of cardiovascular disease.38

A recent study have shown that napping and catch up sleep on weekend paid sleep debt only in 1 in four subjects who restricted their sleep <6hrs.32 75% subjects with sleep debt did not do anything to pay their sleep debt.32 I am worried with this data as these people may not be even aware that their poor health is due to sleep deprivation and they need to take some actions to correct their sleep patterns.

It has been suggested that extending sleep duration over the weekend and taking naps are not good strategies for paying your sleep debt or to prevent metabolic complications arising due to chronic sleep deprivation.32,39

Message for health policy makers based on harmful consequences of chronic sleep restriction

It has been shown that Degree of belief that insufficient sleep can cause outcomes such as moodiness, occupational problems, and health problems may impact whether an individual is contemplating/attempting to change their sleep-related behaviors. Targeting these key messages about the associations between sleep health with moodiness and weight gain in informational material may enhance education/outreach efforts aimed at adults. 40

Links to other blogs:

1. Sleep- Foundation of Health https://www.rem42.ai/blog/sleep-is-the-foundation-of-health/

2. How to sleep well at night? https://www.rem42.ai/blog/how-to-sleep-well-at-night/

References:

1. Basner M, Fomberstein KM, Razavi FM, et al. American time use survey: sleep time and its relationship to waking activities. Sleep. 2007;30(9):1085-1095.

2. Punjabi NM, Bandeen-Roche K, Young T. Predictors of objective sleep tendency in the general population. Sleep. 2003;26(6):678-683.

3. Van Dongen HP, Maislin G, Mullington JM, Dinges DF. The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep. 2003;26(2):117-126.

4. Luyster FS, Strollo PJ, Jr., Zee PC, Walsh JK, Boards of Directors of the American Academy of Sleep M, the Sleep Research S. Sleep: a health imperative. Sleep. 2012;35(6):727-734.

5. Gottlieb DJ, Redline S, Nieto FJ, et al. Association of usual sleep duration with hypertension: the Sleep Heart Health Study. Sleep. 2006;29(8):1009-1014.

6. Soh AZ, Chee MWL, Yuan JM, Koh WP. Sleep lengthening in late adulthood signals increased risk of mortality. Sleep. 2018;41(3).

7. Knutsson A, Hallquist J, Reuterwall C, Theorell T, Akerstedt T. Shiftwork and myocardial infarction: a case-control study. Occupational and environmental medicine. 1999;56(1):46-50.

8. Reither E, Barnet J, Palta M, Liu Y, Hagen E, Peppard P. Polysomnographic Indicators of Restorative Sleep and Body Mass Trajectories in the Wisconsin Sleep Cohort Study. Innov Aging. 2020;4(Suppl 1):636-636.

9. Hartemink N, Boshuizen HC, Nagelkerke NJ, Jacobs MA, van Houwelingen HC. Combining risk estimates from observational studies with different exposure cutpoints: a meta-analysis on body mass index and diabetes type 2. Am J Epidemiol. 2006;163(11):1042-1052.

10. Whitlock G, Lewington S, Sherliker P, et al. Body-mass index and cause-specific mortality in 900 000 adults: collaborative analyses of 57 prospective studies. Lancet. 2009;373(9669):1083-1096.

11. Stutts JC, Wilkins JW, Scott Osberg J, Vaughn BV. Driver risk factors for sleep-related crashes. Accid Anal Prev. 2003;35(3):321-331.

12. Lowrie J, Brownlow H. The impact of sleep deprivation and alcohol on driving: a comparative study. BMC Public Health. 2020;20(1):980.

13. Leng Y, Ackley SF, Glymour MM, Yaffe K, Brenowitz WD. Genetic Risk of Alzheimer’s Disease and Sleep Duration in Non-Demented Elders. Ann Neurol. 2021;89(1):177-181.

14. Spiegel K, Leproult R, Van Cauter E. Impact of sleep debt on metabolic and endocrine function. Lancet. 1999;354(9188):1435-1439.

15. Imeri L, Opp MR. How (and why) the immune system makes us sleep. Nature Reviews Neuroscience. 2009;10(3):199-210.

16. Besedovsky L, Lange T, Born J. Sleep and immune function. Pflügers Archiv – European Journal of Physiology. 2012;463(1):121-137.

17. Prather AA, Pressman SD, Miller GE, Cohen S. Temporal Links Between Self-Reported Sleep and Antibody Responses to the Influenza Vaccine. International Journal of Behavioral Medicine. 2021;28(1):151-158.

18. Saksvik-Lehouillier I, Saksvik SB, Dahlberg J, et al. Mild to moderate partial sleep deprivation is associated with increased impulsivity and decreased positive affect in young adults. Sleep. 2020;43(10).

19. Chung SJ, An H, Suh S. What do people do before going to bed? A study of bedtime procrastination using time use surveys. Sleep. 2020;43(4).

20. Ben Simon E, Vallat R, Barnes CM, Walker MP. Sleep Loss and the Socio-Emotional Brain. Trends Cogn Sci. 2020;24(6):435-450.

21. Wang ID, Liu YL, Peng CK, et al. Non-Apnea Sleep Disorder Increases the Risk of Subsequent Female Infertility-A Nationwide Population-Based Cohort Study. Sleep. 2018;41(1).

22. Liu M-M, Liu L, Chen L, et al. Sleep Deprivation and Late Bedtime Impair Sperm Health Through Increasing Antisperm Antibody Production: A Prospective Study of 981 Healthy Men. Medical science monitor : international medical journal of experimental and clinical research. 2017;23:1842-1848.

23. Chen H-G, Sun B, Chen Y-J, et al. Sleep duration and quality in relation to semen quality in healthy men screened as potential sperm donors. Environment International. 2020;135:105368.

24. Appleton SL, Reynolds AC, Gill TK, Melaku YA, Adams R. Waking to use technology at night, and associations with driving and work outcomes: a screenshot of Australian adults. Sleep. 2020;43(8).

25. St Hilaire MA, Anderson C, Anwar J, et al. Brief (<4 hr) sleep episodes are insufficient for restoring performance in first-year resident physicians working overnight extended-duration work shifts. Sleep. 2019;42(5):zsz041.

26. McHill AW, Hull JT, Cohen DA, Wang W, Czeisler CA, Klerman EB. Chronic sleep restriction greatly magnifies performance decrements immediately after awakening. Sleep. 2019;42(5).

27. Belenky G, Wesensten NJ, Thorne DR, et al. Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose-response study. J Sleep Res. 2003;12(1):1-12.

28. Dinges DF, Pack F, Williams K, et al. Cumulative sleepiness, mood disturbance, and psychomotor vigilance performance decrements during a week of sleep restricted to 4-5 hours per night. Sleep. 1997;20(4):267-277.

29. Rupp TL, Wesensten NJ, Bliese PD, Balkin TJ. Banking sleep: realization of benefits during subsequent sleep restriction and recovery. Sleep. 2009;32(3):311-321.

30. Walsh NP, Halson SL, Sargent C, et al. Sleep and the athlete: narrative review and 2021 expert consensus recommendations. Br J Sports Med. 2020.

31. Jonasdottir SS, Minor K, Lehmann S. Gender differences in nighttime sleep patterns and variability across the adult lifespan: a global-scale wearables study. Sleep. 2021;44(2).

32. Leger D, Richard JB, Collin O, Sauvet F, Faraut B. Napping and weekend catchup sleep do not fully compensate for high rates of sleep debt and short sleep at a population level (in a representative nationwide sample of 12,637 adults). Sleep Med. 2020;74:278-288.

33. Oh YH, Kim H, Kong M, Oh B, Moon JH. Association between weekend catch-up sleep and health-related quality of life of Korean adults. Medicine (Baltimore). 2019;98(13):e14966.

34. Mota MC, Silva CM, Balieiro LCT, Gonçalves BF, Fahmy WM, Crispim CA. Association between social jetlag food consumption and meal times in patients with obesity-related chronic diseases. PLoS One. 2019;14(2):e0212126.

35. Mota MC, Silva CM, Balieiro LCT, Fahmy WM, Crispim CA. Social jetlag and metabolic control in non-communicable chronic diseases: a study addressing different obesity statuses. Scientific Reports. 2017;7(1):6358.

36. Fárková E, Šmotek M, Bendová Z, Manková D, Kopřivová J. Chronotype and social jet-lag in relation to body weight, apetite, sleep quality and fatigue. Biological Rhythm Research. 2021;52(8):1205-1216.

37. Koopman ADM, Rauh SP, van ‘t Riet E, et al. The Association between Social Jetlag, the Metabolic Syndrome, and Type 2 Diabetes Mellitus in the General Population: The New Hoorn Study. J Biol Rhythms. 2017;32(4):359-368.

38. Pan Z, Huang M, Huang J, Yao Z, Lin Z. Association of napping and all-cause mortality and incident cardiovascular diseases: a dose–response meta analysis of cohort studies. Sleep Medicine. 2020;74:165-172.

39. Depner CM, Melanson EL, Eckel RH, et al. Ad libitum Weekend Recovery Sleep Fails to Prevent Metabolic Dysregulation during a Repeating Pattern of Insufficient Sleep and Weekend Recovery Sleep. Curr Biol. 2019;29(6):957-967.e954.

40. Khader WS, Fernandez FX, Seixas A, et al. What makes people want to make changes to their sleep? Assessment of perceived risks of insufficient sleep as a predictor of intent to improve sleep. Sleep Health. 2021;7(1):98-104.

Sleep Health
– Dr Tripat Deep Singh

Sleep Health: A meaningful measure of relationship between Sleep and our health

Sleep health is a new concept to understand the relationship between Sleep and our health. It is recognized now that following multidimensional features characterize “Sleep Health” in young and old adults1,2

  1. Sleep Duration– It refers to how many hours you sleep at night
  2. Sleep Timing– It refers to at what time you go to sleep at night. Different chronotypes prefer either early or late bed times
  3. Sleep Regularity– It refers to having a regular bedtime and wake up time on weekdays and weekends thereby maintaining regular sleep duration
  4. Sleep Efficiency– It refers to how much time you were asleep out of the total time in bed at night and expressed as percentage.
  5. Sleep quality– Subjectively it is assessed by asking the person “how well rested you feel after last night sleep” and it’s one’s personal perception about the quality of their Sleep.

I think it’s better to quantify sleep quality and following parameters of “Sleep continuity” define Sleep quality quantitatively3

  • Sleep Onset Latency (Good Sleep Quality= 0-30 min, Poor Sleep Quality= >45min)
  • Number of awakenings >5 minutes (0-1)
  • Wake after sleep onset (WASO) (<10min or 11-20min) and
  • Sleep efficiency (>95% or 85-94%)

A recent study has also given cut-off values for different dimensions of Sleep health and computed Sleep health score based on these values which showed strong correlation to cardiovascular health.1 I feel it’s a great contribution by the authors in helping to quantify Sleep health.

Currently most of the definitions of “Sleep Deprivation” are based on the Sleep duration and the published literature have looked at the relationship between Sleep duration and the harmful effects on health with conflicting results.4-7

I feel that it’s high time that we start analyzing Sleep as a multidimensional state and consider all the different dimensions to study Sleep health and its relation to our overall health.

Sleep duration does not tell everything about health status

It has been shown that Sleep deprivation as defined by Sleep duration leads to poor health outcomes with conflicting results.4-7 This makes it important to include other parameters of Sleep Health beyond Sleep duration while analyzing someone’s sleep as they have shown important correlations to overall health.

A recent study used three complimentary multivariable modelling approaches for survival endpoints: Cox regression, tree-structured survival analysis, and a random survival forest to study different dimensions of sleep and their relationship to mortality in older men.8 They studies sleep duration, timing, continuity, alertness, quality and rhythmicity. Low sleep continuity and low sleep rhythmicity were associated with all-cause mortality in older people (mean age=76yrs).8 Current sleep recommendations from the National Sleep Foundation9 and the American Academy of Sleep Medicine10 are primarily focused on sleep duration, and this study highlights the importance of other parameters like sleep continuity and rhythmicity and not sleep duration to be associated with all-cause mortality in older people explaining the conflicting results from studies which focused on sleep duration only.

Another study on 1259 subjects, studied the relationship of self-reported sleep duration, sleep quality assessed by Pittsburgh Sleep Quality Index (PSQI) and polysomnography parameters with weight gain.11 The authors reported that poor subjective sleep quality and SpO2<90% were associated with >5Kg weight gain over a 5.3yr follow up period and not sleep duration or other sleep characteristics.11

Absence of Sleep regularity (Irregular sleep duration) and not sleep duration has been shown to be associated with poorer microvascular function as early as young adulthood.12 These findings support the growing body of evidence that irregular sleep patterns may be an independent and modifiable risk factor for CVD.

Questionnaires can also be used to assess multidimensional aspects of Sleep health. RU-SATED is one such questionnaire to assess subjective Sleep health.13 RU-SATED questionnaire takes following dimensions of Sleep into consideration- Satisfaction, Alertness, Timing, Efficiency and Duration. A recent study analyzed relationship between poor sleep health assessed by RU-SATED questionnaire, poor diet and low physical activity with self-reported health status.14 Poor Sleep health defined by RU-SATED questionnaire was associated with poor self- perceived health status, followed by poor diet and low physical activity.14 This study suggests that multidimensional sleep habits and not only sleep duration should be included among the important modifiable health risk factors and be considered a key component of a healthy lifestyle.

Another study included multidimensional aspects of Sleep as assessed by 1 week of actigraphy data including night time sleep duration, wake after sleep onset (WASO), sleep timing, and daytime napping and studied their relationship with cardiometabolic risk score as assessed by Framingham risk score in IT workers and nursing home workers.15 Following Sleep health metrics- more sleep efficiency, less WASO, and less daytime napping (having no naps, fewer naps, and shorter nap duration) were linked to lower cardiometabolic risk score in nursing home workers. Sleep duration was not associated with cardiometabolic risk score.15 This study also highlights the importance of taking napping into consideration while evaluating relationship between multi dimensions of Sleep and overall health. Most of the studies evaluating relationship between sleep duration and different health parameters have not asked about napping habit.

Overall health can be affected by amount of physical activity, age, mental health, intake of medications and comorbid diseases besides poor sleep. All are important for health but it is important to understand how each of these factors affecting health fare against each other for appropriate policy making and prioritizing the resources. A recent study included Multidimensional sleep domain which included-Total Sleep Time, Bed Time, Wake-up Time, Time in Bed, Sleep Efficiency, Sleep Latency, Napping, subjective Sleep quality and the Epworth Sleepiness Scale- was a significant predictor of both all-cause and cardiovascular mortality.16 This study also highlighted that predictive ability of multidimensional Sleep health domain ranked lower than that of the physical health, sociodemographic (including age), mental health, and medication domains, but higher than that of the health behaviors domain and several well-established individual non-sleep predictors (e.g., self-rated health status, heart failure). The most predictive individual sleep characteristics across outcomes were time in bed, hours spent napping, and wake-up time. Authors suggested that future research should develop tools for measuring multidimensional sleep – especially those incorporating time in bed, napping, and timing and not only sleep duration—and test mechanistic pathways through which these characteristics relate to mortality.

In adults there are conflicting reports of association between Sleep duration and obesity.6 Actigraphy based assessment of multidimensional sleep health (sleep efficiency, midpoint, duration, regularity, and self-report measures of alertness and satisfaction ) in women in their middle ages showed no cross-sectional or longitudinal associations between multidimensional sleep health and adiposity.17 This study highlights that the conflicting results in earlier studies may be due to focusing on sleep duration only or including older age populations.

Mindfulness may be a great tool for professionals who constantly face stressful conditions  like nurses. Mindfulness is defined as receptive attention and awareness of what is taking place in the present moment without evaluating it as good or bad.18 a study showed that optimal sleep health (sleep efficiency, duration, regularity, and self-report measures of alertness and satisfaction) is an antecedent of daily mindful attention in nurses. Improving sleep may provide important benefits to their well-being and to the quality of patient care. 19 The authors also reported that at the between-person level, participants with greater sleep sufficiency, higher sleep quality, and fewer insomnia symptoms reported greater mindful attention overall.

Above data highlights the importance of focusing on multidimensional nature of Sleep health and not only sleep duration while monitoring and evaluating the influence of Sleep on health.

Consumer Sleep Technologies (CST’s) do not measure multidimensional aspects of Sleep Health

CST’s have made people get involved with their sleep and also allowed continuous monitoring of Sleep for several nights continuously which was not possible with polysomnography. It helped us to understand various current trends in sleep duration. But, currently available CST’s monitor sleep duration and to the best of my knowledge none of the current CST’s measure multidimensional aspects of Sleep Health which have been shown to be more informative about one’s health.

I hope that in near future CST measuring multidimensional nature of Sleep health become available for more meaningful monitoring of our patients and population Sleep health.

Sleep health as a multidimensional construct is a very welcoming and timely development and I hope to see it becoming the standard of Sleep evaluation in the clinics.

References:

1.           Brindle RC, Yu L, Buysse DJ, Hall MH. Empirical derivation of cutoff values for the sleep health metric and its relationship to cardiometabolic morbidity: results from the Midlife in the United States (MIDUS) study. Sleep. 2019;42(9).

2.           Wallace ML, Yu L, Buysse DJ, et al. Multidimensional sleep health domains in older men and women: an actigraphy factor analysis. Sleep. 2021;44(2).

3.           Ohayon M, Wickwire EM, Hirshkowitz M, et al. National Sleep Foundation’s sleep quality recommendations: first report. Sleep Health. 2017;3(1):6-19.

4.           Kurina LM, McClintock MK, Chen JH, Waite LJ, Thisted RA, Lauderdale DS. Sleep duration and all-cause mortality: a critical review of measurement and associations. Ann Epidemiol. 2013;23(6):361-370.

5.           Cappuccio FP, D’Elia L, Strazzullo P, Miller MA. Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies. Sleep. 2010;33(5):585-592.

6.           Patel SR, Hu FB. Short sleep duration and weight gain: a systematic review. Obesity (Silver Spring). 2008;16(3):643-653.

7.           Itani O, Jike M, Watanabe N, Kaneita Y. Short sleep duration and health outcomes: a systematic review, meta-analysis, and meta-regression. Sleep Med. 2017;32:246-256.

8.           Wallace ML, Stone K, Smagula SF, et al. Which Sleep Health Characteristics Predict All-Cause Mortality in Older Men? An Application of Flexible Multivariable Approaches. Sleep. 2018;41(1):zsx189.

9.           Hirshkowitz M, Whiton K, Albert SM, et al. National Sleep Foundation’s sleep time duration recommendations: methodology and results summary. Sleep Health. 2015;1(1):40-43.

10.        Watson NF, Badr MS, Belenky G, et al. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep. 2015;38(6):843-844.

11.        Häusler N, Heinzer R, Haba-Rubio J, Marques-Vidal P. Does sleep affect weight gain? Assessing subjective sleep and polysomnography measures in a population-based cohort study (CoLaus/HypnoLaus). Sleep. 2019;42(6).

12.        Hoopes EK, Berube FR, D’Agata MN, et al. Sleep duration regularity, but not sleep duration, is associated with microvascular function in college students. Sleep. 2021;44(2).

13.        Buysse DJ. Sleep health: can we define it? Does it matter? Sleep. 2014;37(1):9-17.

14.        Dalmases M, Benítez I, Sapiña-Beltran E, et al. Impact of sleep health on self-perceived health status. Scientific Reports. 2019;9(1):7284.

15.        Buxton OM, Lee S, Marino M, Beverly C, Almeida DM, Berkman L. Sleep Health and Predicted Cardiometabolic Risk Scores in Employed Adults From Two Industries. Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine. 2018;14(3):371-383.

16.        Wallace ML, Buysse DJ, Redline S, et al. Multidimensional Sleep and Mortality in Older Adults: A Machine-Learning Comparison With Other Risk Factors. J Gerontol A Biol Sci Med Sci. 2019;74(12):1903-1909.

17.        Bowman MA, Brindle RC, Joffe H, et al. Multidimensional sleep health is not cross-sectionally or longitudinally associated with adiposity in the Study of Women’s Health Across the Nation (SWAN). Sleep Health. 2020;6(6):790-796.

18.        Brown KW, Ryan RM, Creswell JD. Mindfulness: Theoretical Foundations and Evidence for its Salutary Effects. Psychological Inquiry. 2007;18(4):211-237.

19.        Lee S, Mu C, Gonzalez BD, Vinci CE, Small BJ. Sleep health is associated with next-day mindful attention in healthcare workers. Sleep Health. 2021;7(1):105-112.

Acute Sleep Deprivation
– Dr Tripat Deep Singh

Acute total sleep deprivation refers to wake periods that last beyond 16-18hrs. We all suffer from acute total sleep deprivation at some point of our lives due to one or the other reason.

It is very important to understand the effects of acute sleep deprivation on our brain function as acute sleep deprivation affects our cognitive functions mainly which can lead to road traffic and occupational accidents.

What happens if adults suffer acute total sleep deprivation?

Sometimes we suffer acute sleep deprivation for 1-2 nights due to social engagements or work-related activities or due to some acute stressor. Acute total sleep deprivation affects neuro-cognitive functions mainly-

· Cognitive processing speed is decreased1

· Constructive thinking is affected: It refers to effects on Intra-personal functioning (reduced self-regard, assertiveness, sense of independence, and self-actualization), Interpersonal functioning (reduced empathy toward others and quality of interpersonal relationships), Stress Management skills (reduced impulse control and difficulty with delay of gratification), and Behavioral Coping (reduced positive thinking and action orientation). Also, Esoteric Thinking (greater reliance on formal superstitions and magical thinking processes) was increased.

· Verbal memory is affected3

· Spatial working memory is afected4

· Form more false memories: Five or fewer hours of sleep the night before the experiment were more likely to report that they had witnessed a news event that they did not actually see, compared with rested participants. There was also a trend for these participants to incorporate more misleading information into their memory for visual materials.

· Reduced threshold for stress and elevated stress reaction6,7

Reasoning and complex cognitive tasks remain unaffected by acute total sleep deprivation.8

· Microsleep leading to accidents: One very worrisome development with acute total sleep deprivation is momentary lapses in attention lasting half a second to 10sec or longer which can lead to errors or accidents. This brief lapse in attention has been referred to as “Microsleep”.9 One is not aware of these microsleep episodes.

Performance during sleep deprivation is increasingly variable due to the influence of sleep initiating mechanisms on the endogenous capacity to maintain attention and alertness, thereby creating an unstable state that fluctuates within seconds and that cannot be characterized as either fully awake or asleep.9

· With daytime waking exceeding 16 hours, impairs driving performance to levels equivalent to blood alcohol levels (BAC) levels between 0.05% and 0.1%.

a. In a study of simulated driving performance, impairments in lane-keeping ability after a night without sleep were equivalent to those observed at a blood alcohol content (BAC) of 0.07%.10

b. Similarly, a study of professional truck drivers found that deficits in performance accuracy and reaction time after 28 hours of sleep deprivation were equivalent to those found after alcohol intoxication (BAC at 0.1%).11

There are interindividual differences in deterioration of cognitive functions associated with acute total sleep deprivation.

How long it takes to recover after acute total sleep deprivation?

Shorter periods of sleep deprivation(<12-14hrs) increase NREM, Longer periods of sleep deprivation (>24hrs) increase REM sleep.

Make sure that recovery sleep opportunity duration is >6hrs after 1 or 2 nights of acute total sleep deprivation to speed up the recovery from sleep deprivation. More severe the sleep loss, longer the recovery sleep opportunity required.

Sleep architecture returns to normal on 3 night of recovery sleep after acute sleep deprivation. Following changes are seen in sleep architecture on first 3 nights on recovery from 1 or 2 nights of acute total sleep deprivation-

First recovery night

• Shorter sleep latency

• Less stage W, N1&N2

• Longer TST

• Higher %age of N3

• Lower %age of R

• REM Latency unchanged

Second recovery night

• Increase Stage R

• TST increased

• Stage N3 normal %age of TST

Third recovery night

• Sleep variables approach normal

My advice to all of you is-

· Do not drive or operate heavy machinery If you have suffered from acute total sleep deprivation. Give yourself 3 nights of recovery sleep before engaging in these activities.

· Do not acutely sleep deprive yourself before the exams. Rather sleep well 1-2 nights before the exam after systematic reading during the daytime. I am sure you will fare much better in the exams when you are well slept.

We are becoming a chronically sleep deprived society with detrimental effects on our health. In my next blog I will discuss about Chronic sleep deprivation and its effects on our health.

Until then, sleep well and sleep on time.

Links to other blogs:

1. Sleep- Foundation of Health https://www.rem42.ai/blog/sleep-is-the-foundation-of-health/

2. How to sleep well at night? https://www.rem42.ai/blog/how-to-sleep-well-at-night/

References:

1. Banks S, Van Dongen HP, Maislin G, Dinges DF. Neurobehavioral dynamics following chronic sleep restriction: dose-response effects of one night for recovery. Sleep. 2010;33(8):1013-1026.

2. Killgore WD, Kahn-Greene ET, Lipizzi EL, Newman RA, Kamimori GH, Balkin TJ. Sleep deprivation reduces perceived emotional intelligence and constructive thinking skills. Sleep Med. 2008;9(5):517-526.

3. Harrison Y, Horne JA. Sleep loss impairs short and novel language tasks having a prefrontal focus. J Sleep Res. 1998;7(2):95-100.

4. Heuer H, Kohlisch O, Klein W. The effects of total sleep deprivation on the generation of random sequences of key-presses, numbers and nouns. Q J Exp Psychol A. 2005;58(2):275-307.

5. Frenda SJ, Patihis L, Loftus EF, Lewis HC, Fenn KM. Sleep deprivation and false memories. Psychol Sci. 2014;25(9):1674-1681.

6. Minkel JD, Banks S, Htaik O, et al. Sleep deprivation and stressors: evidence for elevated negative affect in response to mild stressors when sleep deprived. Emotion. 2012;12(5):1015-1020.

7. Minkel J, Htaik O, Banks S, Dinges D. Emotional expressiveness in sleep-deprived healthy adults. Behav Sleep Med. 2011;9(1):5-14.

8. Goel N, Rao H, Durmer JS, Dinges DF. Neurocognitive consequences of sleep deprivation. Semin Neurol. 2009;29(4):320-339.

9. Doran SM, Van Dongen HP, Dinges DF. Sustained attention performance during sleep deprivation: evidence of state instability. Arch Ital Biol. 2001;139(3):253-267.

10. Fairclough SH, Graham R. Impairment of driving performance caused by sleep deprivation or alcohol: a comparative study. Hum Factors. 1999;41(1):118-128.

11. Williamson AM, Feyer AM. Moderate sleep deprivation produces impairments in cognitive and motor performance equivalent to legally prescribed levels of alcohol intoxication. Occup Environ Med. 2000;57(10):649-655.

How to Sleep well at night?
– Dr Tripat Deep Singh

A lot of sleep disorders can disturb your sleep at night. Insomnia is one of the sleep disorders and is defined as trouble falling asleep or staying asleep at night. There are different factors that can contribute to Insomnia including bad sleep habits, consuming substances or having a bad sleeping environment that is not conducive for falling or maintaining Sleep.

When I see a patient, who complains of difficulty falling asleep or maintain sleep at night, I try to determine the underlying cause for the patient’s problem. Detailed medical and sleep history is taken which allows me to determine what might be causing the problem.

Sleep hygiene include behaviors around sleep timing, pre-bed routines and sleeping environment. I enquire in detail about patient’s behaviors regarding the sleep wake schedule on weekdays and weekends and napping habits, regarding patient’s pre-bed routines including timing of dinner and exercise and about sleeping environment including temperature, humidity, light, sound, mattress, pillows. Any of these factors can be the cause or perpetuating factor for Inadequate sleep hygiene Insomnia.

Addressing inadequate sleep hygiene may not cure other types of Insomnia not due to inadequate sleep hygiene but may help to augment the clinical gains of other treatments and help to prevent recurrence.

This makes it very important for me to identify the underlying cause of Insomnia, have a detailed discussion with patient regarding their Sleep hygiene habits, identify the bad sleep hygiene habits and explain to them the rationale for each advice regarding improving their sleep hygiene habits.

In today’s Google world, many patients have been exposed to the list of good Sleep hygiene habits on the internet and many have tried practicing them on their own. But I feel more important than the list is patients understanding of the sleep wake regulation and the science behind each of the Sleep hygiene tips for them to adhere to the treatment and benefit from it. I will share an example here of one of my patients who had problem falling asleep at night. This patient was trying to have increased deep sleep at night as compared to REM. He was monitoring his sleep with a smart watch and every morning will look whether deep sleep have increased or not with his different sleeping tricks at night. This patient had no clear understanding regarding how sleep is distributed throughout the night and no need to increase particular sleep as long as it is within normal duration. Explanations around the types of sleep, distribution and importance of sleep at night helped the patient to stop worrying about increasing the deep sleep and helped him to have easy sleep onset as his mind was relaxed before going to sleep.

I am sharing with you good Sleep hygiene tips for you to have better night Sleep but I will suggest that if you have trouble falling or maintaining sleep and you have either good or poor Sleep hygiene, consult a Sleep physician for the right cause to be identified underlying the Insomnia before we try only good Sleep hygiene tips without any improvement and labelling them as a failure to cure your Insomnia problem. Identifying the right cause, instituting the right treatment along with good Sleep hygiene can do wonders to cure your Insomnia problem. There may be another underlying sleep disorder other than Insomnia contributing to your sleep problems. Sleep Physician will be able to assess the right cause and start the right treatment for your Sleep disorder.

Sleep Hygiene tips for Adults

Sleep hygiene tips are simple recommendations that may influence length and improve the quality of sleep by modification of habits, behaviors and environmental conditions. There is a lot of clinical evidence regarding good sleep hygiene and improved Sleep and performance.

  • Bad Sleep hygiene practices like using nicotine late in the evening, light or noise disturbance, and having an irregular sleep schedule have been shown to be associated with concurrent and future Insomnia.1
  • In athletes with poor sleep, following Sleep hygiene advice has been shown to improve Sleep and enhance athletic performance.2 Banking sleep (sleep extension prior to night of intentional sleep deprivation before sporting event) is a new concept that may also improve performance.2
  • Sleep hygiene principles have been shown to benefit postmenopausal women who suffer from insomnia.3
  • Combined light exposure and sleep hygiene improved speed and power but not intermittent-sprint performance up to 96 hours following long-haul transmeridian travel.4
  • Sleep hygiene maintenance helps persons living with diabetes enjoy a better quality of life by restoring normal sleep patterns and thereby improving glycaemic control.5

I will be sharing 20 tips to improve Sleep hygiene for better night Sleep under following categories-

  • Behaviour change
  • Healthy pre-sleep routine
  • Improving bedroom environment

Behaviour change

Tip1: Have a regular Sleep-wake schedule on weekdays and weekends

Having a consistent sleep wake schedule on weekdays and weekends helps you to keep your circadian system aligned to the light and dark cycle. Circadian system not only controls your Sleep- Wake cycle but also controls your metabolic functions, temperature rhythms, appetite and hormone rhythms.

Another issue with not maintaining a regular sleep-wake schedule on weekdays and weekends is that one tend to accumulate “Sleep debt”. Now-a-days people sleep less on weekdays due to work pressure or lifestyle changes and try to sleep more on weekends to make up for lost Sleep. When someone is sleeping less than what is required, they accumulate “Sleep debt” eg: if someone needs 7hrs Sleep per night and sleep only 6hrs, then the person is accumulating 1hr of Sleep debt per day. Sleep debt is additive, if you are sleeping 1 hr less every night then sleep debt gets accumulated over the week.

Sleep debt has been defined as difference >60min between total sleep time required for the person and actual sleep hours obtained on weekdays. Severe sleep debt is difference >90min between total sleep time required for the person and actual sleep hours obtained on weekdays.6

I usually suggest my patients that having a regular sleep-wake schedule on weekdays and weekends helps you to avoid accumulating Sleep debt in the first place along with its harmful consequences on the health.

One can follow following tips to achieve regular sleep-wake schedule and avoid sleep debt-

  1. Determine your Sleep need: Along with your Physician try to understand how much Sleep is required by you. Each individuals Sleep requirements are different. Age specific guidelines on Sleep requirements have been published by National Sleep Foundation which can be referred for recommendations.
  2. Set your sleep and wake up time: Set you Sleep and wake up time according to the number of hours of Sleep required by you as determined along with your physician. Smart devices now-a-days can help you to set reminders for your Sleep time 1 hr before your scheduled time for Sleeping so that you can start winding down and get ready for sleep on time.
  3. Avoid Sleep disturbing activities during daytime: Avoid any daytime activities that may interfere with night time Sleep like drinking caffeine 4-6hrs before sleep time, consuming alcohol, having heavy dinner or exercising too close to bedtime.
  4. Comfortable bedroom environment: Try to have a comfortable bedroom environment with right temperature, humidity and sound levels, a comfortable mattress, pillows or linen which helps you to sleep better. Please read tips on improving bedroom environment in this blog for more specific details on how to achieve a comfortable bedroom environment.
  5. Stop doing work 1 hr prior to your sleep time: Start preparing yourself for Sleep at least 1 hr prior to your scheduled sleep time. Read more tips about changing your pre-sleep routine in this blog.

If you have already accumulated Sleep debt, then in addition to above tips for maintaining regular sleep-wake schedule you can follow following tips to pay your sleep debt-

  1. Determine your Sleep need: Along with your Physician try to understand how much Sleep is required by you.
  • Give yourself sometime: Increase your Sleep at night in increments of 15-30min every night until you reach your goal of sleep duration as determined along with your Physician. It may take some time to pay your sleep debt depending upon how much Sleep debt has been accumulated and if you do not continue to accumulate sleep debt.
  • Napping and weekend catch up sleep: The practice of sleeping more on weekend to make up for lost sleep on weekdays has been referred to as “Weekend Catch up Sleep”.One can try napping and weekend catch up Sleep to pay your sleep debt but these two should not be your primary methods to pay your sleep debt.

While sometimes life’s situations make us to lose sleep on weekdays and catching up on Sleep and napping over the weekend may make us feel better but it should not become a routine once the situations improve. Accumulating sleep debt on weekdays and sleeping longer on weekends may give you a false sense of well-being but the Sleep debt snow balls over a period of time.

Studies have shown that napping and weekend catch up sleep compensated for severe sleep debt only in 1 in 4 cases only.6 Also studies have shown that if you accumulate 1 hr of sleep debt it may take 4 nights of adequate Sleep to pay that debt.7

If you are feeling sleepy during daytime despite sleeping as per your body needs and not accumulating sleep debt, please consult a Sleep Physician to screen for any underlying Sleep disorder.

Tip2: Avoid Naps 6-8hrs before Sleep time

Two processes regulate Sleep- Homeostatic process (Process S) and circadian process (Process C). Process S is the sleep pressure that builds up during the day while you are awake. Longer you are awake, higher the sleep pressure.

Napping during the daytime takes off the sleep pressure and makes it difficult to fall asleep during the night time.

Some of my patients especially retirees tell me that they have free time in the afternoon to take a nap and they feel fresh after that. I usually tell them to avoid naps as occasional naps may lead to regular napping via conditioning and this may alter the sleep wake timing and affect sleep homeostasis.

My advice to my patients is nap only if necessary to maintain alertness. If it is necessary to take a nap then try to keep the duration of the nap to 10-20min only8 and try to have the nap in the morning or early afternoon as it will not interfere with night time Sleep. Taking a nap after 3pm will definitely interfere with your night time Sleep as it will reduce the Sleep pressure built up during the day. My general advice to my patients is to avoid naps after 3pm or 6-8hrs before regular sleep time to avoid altering Sleep homeostasis.

Some patients complain that if they take a nap for 1-2hrs in the afternoon they wake up groggy rather than fresh. This feeling of grogginess after a long nap is referred to as “Sleep Inertia”.8 This happens as long nap allows you to enter Stage N3 Sleep and you feel groggy when you wake up from stage N3 sleep. Keeping the nap short to 10-20min duration does not give you enough time to enter Stage N3 sleep and you wake up fresh from the short nap.

If you are sleepy during daytime despite having sleep duration as per your body needs as determined along with your Sleep physician and despite having naps, there may be an underlying Sleep disorder for which you may need Sleep Physician consultation.

Healthy pre-sleep routine

Tip3: Try relaxing 1hr prior to your Sleep time

At night levels of melatonin hormone, secreted from Pituitary gland, starts increasing. Melatonin hormone promotes Sleep. On the other hand, levels of Cortisol hormone decrease throughout the night in sleeping period. Cortisol is the stress hormone and its levels starts increasing just before waking up to get us ready for the stresses of the daily life. At night if we are stressed, it activates stress response which causes release of cortisol and increased cortisol levels promotes wakefulness.

Relaxing before sleep avoids stress response from being activated and releasing cortisol which cause wakefulness.

One can try any of the following techniques to relax- Mindfulness meditation, guided imagery, hypnosis, progressive muscle relaxation, and deep breathing.

One can try Techniques with physical component such as yoga, tai-chi and qi gong.9

If worrying thoughts about next day or future trouble you and you are unable to fall asleep, my personal advice is try writing these worrying thoughts in a diary which has helped a lot of my patients to fall asleep. Write down specific to-do-list for 5 minutes rather than chronicling all completed activities. It has been shown in a study that participants who wrote to-do-list fell asleep faster than participants who just wrote about completed activities.10

Take 5min to be thankful for all the blessings of your life, lie down comfortably, close your eyes, breathe slowly and being thankful let the Sleep embrace you.

Tip4: Take Hot shower 1-2hrs before Sleep time for 10min

Core Body temperature have circadian rhythm with peak in late afternoon and early evening and falls at the onset of Sleep. One sleeps on falling temperature curve of the body.

Taking hot shower increases the temperature of body extremities which is detected by heat sensing centres in the brain. Heat sensing centres detect increased temperature of the extremities and activate the cold response which dilates the blood vessels in extremities leading to heat loss which drops the body core temperature. Falling of body core temperature helps one to fall asleep easily.11

I tell my patients not to take a hot shower immediately before going to bed as it will raise the core body temperature and make it difficult to fall asleep. A hot shower should be taken 1-2hrs prior to your scheduled sleep time to provide enough time for your core body temperature to fall which will assist with sleep onset.

Tip5: Do Regular exercise but 90min before Sleep time

Core Body temperature have circadian rhythm with peak in late afternoon and early evening and falls at the onset of Sleep. One sleeps on falling temperature curve of the body.

Exercising too close to bed time will increase the core body temperature which will make falling asleep difficult.

I advise my patients to exercise at least 90min before Sleep time.  This will increase core body temperature also but provides some time for the core body temperature to fall by the time one goes to Sleep.12 You can do following to set your exercise routine-

  1. Determine your Sleep need: Along with your Sleep Physician try to understand how much Sleep is required by you. Each individuals Sleep requirements are different.
  2. Set your sleep and wake up time: Set your Sleep and wake up time according to the number of hours of Sleep required by you as determined along with your physician.
  3. Set an exercise time at least 90min away from your set sleep time. You can set a reminder for set exercise time on your smart devices.

Tip6: Avoid heavy meals 2-3hrs before Sleep time

Having dinner 2-3hrs before bedtime decrease number of nocturnal awakenings, makes it easy to fall asleep and increases total sleep time in healthy young adults.13

There are circadian rhythm system in your body which controls your sleep-wake cycle, metabolism, hormone levels  and many other bodily functions. The master clock to set the rhythms is a small structure in your brain called “Suprachiasmatic nucleus”. Each cell in your body have its own clock (Peripheral clocks) which is in tune with your master clock if you have healthy circadian system. Light, food, sleep and wakefulness helps to entrain our circadian system. Master clock have influence on peripheral clocks which in turn can influence the master clock.

If you eat a heavy meal very close to your sleep time, food may reset your peripheral clocks in liver and other gut organs to digest food and this may cause peripheral clocks not to be in tune with your master clock. In simple terms, master clock may be putting you to sleep but your peripheral clocks are keeping the organs active which have its own health consequences.

I advise my patients to have a light meal at least 2-3hrs before their sleep time to maintain synchrony between their master and peripheral clocks. Eating a light meal 2-3hrs before sleep time gives enough time for digestion to happen and maintain healthy circadian system and good quality Sleep.

Avoid eating spicy foods, red meat and carbonated beverages at night. Choose a light carbohydrate rich diet at night.

You can start with setting a reminder to eat 2-3hrs before sleep time until it becomes a habit.

Tip7: Listen to relaxing music

Listening to relaxing music especially including naturalistic sounds helps to feel pleasant and decrease distractions.14

Choose anything in classical music or natures sounds to relax you. You will need to try  couple of music pieces to see which ones relax you the most. Like in my case after a lot of listening, I have chosen Indian classical ragas which are specific to night time like Raga JaiJaiwanti, Raga Des, Raga Darbari as they help me to relax and go to sleep in a very relaxed manner.

One can do following-

  1. Dim the lights 1hr before your sleep time,
  2. Keep the gadgets away
  3. Switch on your chosen piece of music
  4. If you are playing music on your phone/tablet or PC, make sure to switch off all the notifications for this one hour and possibly for the night.

Tip8: Allow 3-4hrs between drinking alcohol and Sleep time

Alcohol intake decreases time to fall asleep. But it disturbs Sleep architecture in several ways which make you wake up not feeling refreshed. Alcohol intake close to sleep time have the following effects15

  • The onset of the first REM sleep period is significantly delayed
  •  Reduction in total night REM sleep.
  • Increase in slow wave sleep (SWS) in the first half of the night relative to baseline values
  • Aggravates OSA
  • Cause more urination and disrupt sleep
  • Increase risk of Parasomnias

My advice to you regarding drinking is as follows-

  • Avoid drinking before sleep time
  • If you have to drink then Allow 3-4hrs between drinking and Sleep time
  • Stay hydrated and drink water
  • Avoid bubbly drinks as they cause bloating and gas
  • Eat a light snack before bedtime

Tip9: Do not consume a lot of caffeine 4-6hrs before Sleep time

Two processes regulate Sleep- Homeostatic process (Process S) and circadian process (Process C). Process S is the sleep pressure that builds up during the day while you are awake. Longer you are awake, higher the sleep pressure.

The neurotransmitter for Process-S is Adenosine. Adenosine levels in your brain increase with increasing wakefulness and makes us feel sleepy. Caffeine blocks adenosine receptors and hence adenosine action producing state of alertness/wakefulness.

400 mg of caffeine taken 0, 3, or even 6 hours prior to bedtime significantly disrupts sleep.

Even at 6 hours, caffeine reduced sleep by more than 1 hour.16

Even a single cup of caffeinated coffee (90mg) consumed before bedtime in real-life conditions causes a deterioration in the quality of sleep in caffeine-sensitive subjects.17

Just say no to any caffeinated or energy drink after 3pm if you are sensitive to caffeine.

Tip10: Drink a warm glass of milk or a light snack  before bedtime18

Drinking a warm glass of milk or a light snack may help to prevent fall of blood glucose levels at night which can disturb sleep.

Carbohydrates like crackers, bread, cereals and fruits are best for a good night Sleep. Try to avoid chocolates or heavily sweetened foods as snacks.

Please talk to your Physician If you are intolerant to lactose or milk.

Tip11: Do not smoke 4-6hrs before Sleep time

Nicotine is a stimulant and promotes wakefulness. Late evening use of nicotine has been shown to cause Insomnia and increases the risk to develop Insomnia at 1yr.1

Try following if you are a chronic smoker with difficulty sleeping-

  1. Try to enroll in “quit smoking” program
  2. Try nicotine patch
  3. Avoid smoking in the middle of the night if you wake up and cannot go back to sleep
  4. Try changing the timing of smoking 4-6hrs away from bedtime and see if it helps

Improving Bedroom Environment

Tip12: Ensure bedroom is only used for sleep or intimacy

The scientific principle for this advice is to develop a Conditioning response to identify the bed & the bedroom with sleep & not a place for other activities.

My advice regarding using bedroom only for sleep or intimacy is-

  1. Take out the television out of your bedroom,
  2. Keep all gadgets out of the bedroom for the night
  3. Keep an ordinary clock in your room and not a digital clock or any smart watch or gadgets be used as watch
  4. Do not play games or do household chores in your bed

Tip 13: Bedroom environment should be quiet

Some people are not easily awakened by slight noises at night but some are very sensitive to even the slightest of the sound which will wake them up. People who get easily disturbed by noise should try to reduce noise levels or acoustically isolate the room which helps to increase deep sleep.19

One can use ear plugs also to block noise. They reduce noise levels by 30-35 dB.19 White noise can be used to improve sleep quality if your sleep is disturbed by environmental noise.20 But if you are caregiver, please do not use ear plugs as you may not be able to hear the call when called for any help or support.

Tip14: Maintain ambient bedroom temperature and humidity

Different people prefer different room temperature and humidity levels comfortable enough for Sleeping. I am sharing some scientific data that has been published with regards to room temperature and humidity levels for a comfortable sleep, which may be useful to some of you-

  • Try to Maintain room temperature of 27-30 degree Celsius21 with a humidity of 50-70%22 for good Sleep. In daily life, the use of air conditioning in the initial sleep hours can protect sleep and thermoregulation.22
  • Another approach that has been suggested for refreshing awakening is to gradually decrease room temperature from 27 degrees C to 24 degrees C between 1800 and 2200 h and gradual increase from 24 degrees C to 27 degrees C between 0300 and 0700 h promoted sleep and fresh awakening and increased melatonin levels at night.23

Tip15: Try to have comfortable bedding accessories

The choice of bedding accessories (comfortable pillow, quilt, bed sheets, night clothing) for good night sleep is also very personal and can vary from person to person. I am sharing some scientific data that has been published with regards to choosing bedding accessories for a comfortable sleep, which may be useful to some of you-

  • Comfortable pillows made of special material help reduce core body temperature and improve Sleep24
  • Proper choice of quilts also decrease core body temperature better and improve Sleep25
  • Use of electric blanket in winters can help to improve Sleep stability and thermoregulation during Sleep26
  • Wearing socks at 23 degree Celsius room temperature with 50% relative humidity improves Sleep quality27

I usually advice my patients to change their pillows at least once in every 1-3years or earlier if they wear out.

Tip16: Choose a comfortable mattress

Choice of mattress for good night sleep is again a very personal choice. I will share some scientific data on which mattress features have been shown to have a positive effect on Sleep which may allow some of you to make an informed decision while choosing your own mattress for a good night Sleep-

  • Prefer a mattress which provides head and back cooling28
  • A mattress with high rebound topper provides more restorative Sleep29
  • Prefer a mattress with high heat capacity as it improves deep sleep30
  • Medium firm or firm mattress may benefit back pain31
  • Prefer a mattress which provides support to your shoulders and hip32
  • If you have Positional OSA, sleeping on a specially designed pillow and mattress reduces severity of OSA and improves oxygenation33
  • If you are prone to back pain, avoid sleeping on a foam mattress as it can lead to back pain34

I do enquire about when was the last time they changed their mattress as sleeping on worn out mattress can disturb sleep. I usually advice my patients to change their mattress at least once in a decade or earlier if mattress is worn out and disturbing their Sleep.

Tip17: Keep bedroom dark and screen free

Hormone Melatonin is released from Pineal gland with onset of darkness and melatonin helps with sleep onset. Melatonin levels are highest during Sleep and its secretion is inhibited with daylight especially the blue wavelength.

Reducing evening blue light advances sleep and melatonin.35 Use of Blue-light-blocking lenses (89-99,9% filter of blue light between 400-500 nm, general decrease of light intensity: 50%) 9hrs before switching off the lights advanced sleep and melatonin levels.35

Use of any type of screen- smart phone, tablet or computer- suppresses melatonin secretion and delays sleep onset because all these devices emit light with blue wavelength which suppresses melatonin secretion.36

Avoid reading ebooks on tablets at night as it has been shown that reading a story from an iPad decreased subjective sleepiness, delayed the EEG dynamics of slow wave activity by approximately 30 min.37

My personal advice to all of you is as follows-

  • Turn off overhead lights two hours before bed, and switching to dimmer table lamps
  • And if you do use a computer or smartphone in the evening, install an app that automatically dims the screen and filters out the blue light
  • Keep all electronic gadgets out of your bedroom
  • Do not check time on your smart phone if you wake up in the middle of the night. Try to go back to sleep without worrying about the time of the night.
  • Try to have heavy curtains cover the window to cut of any unwanted light coming into your bedrooms.

Tip18: Use Aromatherapy (Lavender and Peppermint)

Choice of the aroma to relax oneself can vary from person to person. I will share some of the scientific data showing that some particular fragrances helped to improve Sleep in specific patient populations and we all can try these fragrances to see if we derive the same benefits as highlighted in these studies-

  • Lavender essential oil increased quality of sleep and reduced level of anxiety in patients with coronary artery disease38
  • Peppermint and Lavender oil aromatherapy improved sleep quality in cancer patients39
  • Application of Lavender cream improved Sleep quality in pregnant ladies40
  • Lavender and sleep hygiene together, and sleep hygiene alone to a lesser degree, improved sleep quality for college students with self-reported sleep issues41

Tip19: Keep room air Clean

If room air is not clean, it may irritate your air passages leading to sneezing, coughing or asthma attack disturbing your sleep.

One can try following to keep room air clean-

  • Avoid smoking inside room. It increases levels of toxic chemicals in room air as compared to non-smokers room42
  • Maintain good airflow using either ceiling fan or air conditioner43
  • If you have OSA, indoor air pollution can aggravate severity of OSA which can disturb your Sleep44
  • Avoid sleeping with pets in the room if you are allergic to their hair

Try using air purifier if air quality is really bad in your area.

Tip20: Limit the time you spend awake in bed

The idea behind this advice is scientific principle of “Paradoxical Intention” which states that the harder one tries to sleep farther away it gets.

If awake in bed for 15-20 minutes, get up & leave bedroom. Engage in quiet activity like reading a book, listening to relaxing music or meditation until drowsy again.

Do not engage yourself to watch movies, listen to disturbing music or switch on the bright lights. If you need to navigate the room, try to have a dim light by your bedside.

I hope these tips help you to Sleep better at night. In my next blog I will be discussing about harmful effects of sleep deprivation on our health. Until then- Sleep well and sleep on time.

References:

1.         Jansson-Fröjmark M, Evander J, Alfonsson S. Are sleep hygiene practices related to the incidence, persistence and remission of insomnia? Findings from a prospective community study. J Behav Med. 2019;42(1):128-138.

2.         Vitale KC, Owens R, Hopkins SR, Malhotra A. Sleep Hygiene for Optimizing Recovery in Athletes: Review and Recommendations. Int J Sports Med. 2019;40(8):535-543.

3.         Duman M, Timur Taşhan S. The effect of sleep hygiene education and relaxation exercises on insomnia among postmenopausal women: A randomized clinical trial. Int J Nurs Pract. 2018;24(4):e12650.

4.         Fowler PM, Knez W, Thornton HR, et al. Sleep Hygiene and Light Exposure Can Improve Performance Following Long-Haul Air Travel. Int J Sports Physiol Perform. 2020;16(4):517-526.

5.         Sousa A, Kalra S. Sleep hygiene and diabetes: Suggestions for primary care. J Pak Med Assoc. 2017;67(5):814-815.

6.         Leger D, Richard JB, Collin O, Sauvet F, Faraut B. Napping and weekend catchup sleep do not fully compensate for high rates of sleep debt and short sleep at a population level (in a representative nationwide sample of 12,637 adults). Sleep Med. 2020;74:278-288.

7.         Kitamura S, Katayose Y, Nakazaki K, et al. Estimating individual optimal sleep duration and potential sleep debt. Sci Rep. 2016;6:35812. 8.         Brooks A, Lack L. A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recupera

Sleep : Foundation of health
– Dr Tripat Deep Singh

Now-a-days Sleep is defined as fifth pillar of health along with other four pillars- nutrition, exercise, mind/emotions and social/personal relationships. But I believe sleep is not fifth pillar, rather it is the foundation on which four pillars of nutrition, exercise, mind/emotions and social/personal relationships are standing to support good health.

Sleep is the foundation of health

For millions of years our ancestors have only moon light as the source of light at night. They will Sleep at night and during daytime go outside and get exposed to sunlight. Our ancestors had 12 hrs of day and 12hrs of darkness. The bodies adapted to this 12hrs day and darkness and developed certain rhythms, each rhythm following a particular time of the day or night eg: Sleep happening at night.

With the discovery of fire, our ancestors were exposed to artificial light at night for the first time which allowed them to be awake a little later into night as they could spend some time on cooking in a safe environment away from predators. This happened 300,000 years ago with daily usage of fire and probably made it possible to sleep on ground.1

In 19th century, Thomas Edison invented the bulb and changed our lives forever. Our homes and cities are now lit with bright light at night and work had been made possible 24hrs around the clock under well-lit conditions.

In 20th century, smart phones were invented. People often use these smart phones at night after getting into the bed and switching off the room lights. Now they get exposed to artificial light even in darkness after retiring to the bed, at a time when their bodies are looking forward to Sleeping.

Millions of years of evolution prepared our body to Sleep when the darkness sets in. There are physiological changes happening in our bodies with onset of darkness, which helps us to Sleep eg: Melatonin hormone is secreted with the onset of darkness which puts us to Sleep. Our ancestors had 7-9hrs of Sleep in 12hrs of darkness.

But in last 100-150 yrs we have decreased the duration of darkness and now we try to pack 7-9hrs of Sleep in 8-10hrs of darkness. Shift work made possible with a lot of technologies and most importantly well-lit conditions of our buildings, has even made us to pack 7-9hrs of Sleep during daytime with consequent health consequences.

This change in our behavior happened on a very small-time scale as far as evolution is concerned, which have not given enough time for our bodily functions to adapt to these lifestyle changes.

Light at night suppresses melatonin secretion and delays onset of Sleep.

Use of any type of screen- smart phone, tablet or computer- suppresses melatonin secretion and delays sleep onset because all these devices emit light with blue wavelength which suppresses melatonin secretion.2

Avoid reading ebooks on tablets at night as it has been shown that reading a story from an iPad decreased subjective sleepiness, delayed the EEG dynamics of slow wave activity by approximately 30 min.3

Reducing evening blue light advances sleep and melatonin.4 Use of Blue-light-blocking lenses (89-99,9% filter of blue light between 400-500 nm, general decrease of light intensity: 50%) 9hrs before switching off the lights advanced sleep and melatonin levels.4

Sleep is a universal phenomenon

Sleep is seen almost in all species on earth. Sleep must be serving some important function for our survival as the evolutionary process have not eliminated it during natural selection.

Sleep is a recurring state characterized by:

  • Reduced awareness of and interaction with the external environment
  • Reduced mobility and muscular activity
  • Partial or complete cessation of voluntary behavior and awareness of self in the environment (reversible)

Types of Sleep:

There are two types of Sleep-

  1. Non rapid eye movement Sleep (NREM)
  2. Rapid eye movement Sleep (REM): Also called as dream Sleep

NREM Sleep have three substages-

  1. Stage N1
  2. Stage N2
  3. Stage N3: Also called as Deep sleep or slow wave sleep

A healthy person spends 75-80% of our sleep time in NREM and 20-25% of sleep time in REM Sleep every night.

Out of 75-80% of time in NREM sleep, we spend 3-8% of sleep time in Stage N1, 45-55% in Stage N2 and 15-20% in Stage N3 sleep.

We are awake for some time after we go to bed before we fall asleep. There is progression of sleep through cycles once we fall asleep.

Sleep cycle:

Sleep cycle is defined as progression of Sleep at night. A healthy adult enters first into NREM sleep and then REM sleep. Most of the healthy adults follow progression from Stage N1-Stage N2-Stage N3-Stage REM.

Stages N1, N2,N3 can vary in order of progression but it’s always NREM followed by REM sleep. Adult entering sleep via REM sleep may indicate sleep deprivation or an underlying Sleep disorder.

One episode of NREM followed by one episode of REM constitutes one Sleep cycle. There are 4-6 Sleep cycles in one night.

Timeline of Sleep to wake up events

One need to understand few concepts regarding what happens from the moment we go to bed until we wake up in the morning.

Fig: 1 Timeline of Sleep to wake up events. TST= Total Sleep Time, TWT= Total Wake Time, WASO= Wake after sleep onset.

Once a person is sleepy, they prepare the room for Sleep and then lie down in bed and switch of the lights.

Most of us take some time to fall asleep after lying down. This time from lying down to falling asleep is called “Sleep onset latency (SOL)”. For a healthy person SOL=10-20min. If SOL>30min, diagnosis of Sleep onset Insomnia is made.

Many people do not wake up at all after falling asleep and many wake up 0-1 times in the middle of the night. The time one spends awake after falling asleep is called “Wake after sleep onset (WASO)”. While awake, patient may just lie in bed or may go to bathroom to pass urine, drink water or may engage in any other activity. 0-1 awakenings of <5min are considered normal and WASO of <10min or 11-20min is considered normal.

The total time one spends asleep at night is called “Total Sleep Time (TST)”. We also calculate how much time was spent in bed. Total time spent in bed is referred to as “Time in Bed (TIB)”.

Ratio of TST/TIB gives an estimate of “Sleep Efficiency (SE)”. SE>95% OR 85-94% is considered normal

One wakes up in the morning, stays in bed for some time or gets out of the bed immediately and then is ready for the daily activities.

Defining good night Sleep

One should take care of three things for a good night Sleep-

  1. Sleep Regularity
  2. Sleep Duration
  3. Sleep Quality
  4. Attention to your chronotype

Sleep Regularity

Maintain a regular bed time and wake up time on weekdays as well as weekends.

Now-a-days people sleep less on weekdays due to work pressure or lifestyle changes and try to sleep more on weekends to make up for lost Sleep. When someone is sleeping less than what is required, they accumulate “Sleep debt” eg: if someone needs 7hrs Sleep per night and sleep only 6hrs, then the person is accumulating 1hr of Sleep debt per day.

Sleep debt has been defined as difference >60min between total sleep time required for the person and actual sleep hours obtained on weekdays. Severe sleep debt is difference >90min between total sleep time required for the person and actual sleep hours obtained on weekdays.5

The practice of sleeping more on weekend to make up for lost sleep on weekdays has been referred to as “Weekend Catch up Sleep”. Studies have shown that napping and weekend catch up sleep in adults compensated for severe sleep debt (>90min) only in 1 in 4 cases only.5

Sleep Duration

The total time one spends asleep at night is called “Total Sleep Time (TST)”. Each individuals Sleep requirements are different. Age specific guidelines on Sleep requirements have been published by National Sleep Foundation which can be referred for recommendations. It is summarized in Fig 2.

The first step to wake up fresh in the morning is to determine how much Sleep you need at night by working along with your Sleep Physician. Once you know the amount of Sleep you need, set your bed and wake up time accordingly.

Fig 2: National Sleep Foundation TST recommendations for different age groups

Sleep quality

In the clinic we use following National Sleep Foundation defined indicators of good sleep quality to assess patients Sleep quality 6

  • Sleep Onset Latency (Good Sleep Quality= 0-30 min, Poor Sleep Quality= >45min)
  • Number of awakenings >5 minutes (0-1)
  • Wake after sleep onset (WASO) (<10min or 11-20min) and
  • Sleep efficiency (>95% or 85-94%)

Many studies assess Sleep quality subjectively by asking one question “How was the quality of your sleep last night?” on a scale of 1 (very good) to 5 (very bad).7

If you are feeling refreshed upon awakening and did not need an alarm clock to wake you up, it is a good sign that you are getting both the quantity and quality that you need.

Pay attention to your Chronotype

Chronotype is defined as the internal circadian rhythm or body clock of an individual that influences the cycle of sleep and activity in a 24-hour period.

Traditionally three types of chronotypes have been proposed that prefer to Sleep and wake up at different times of the day.

  1. Morning type: Also called larks. These people prefer to wake up early in the morning and go to bed at around 10pm.
  2. Evening type: Also called night owls. They stay late up at night and wake up late in the morning.
  3. Neither

There are different ways to determine your chronotype-

  1. Using questionnaires like Horne-Ostberg questionnaire
  2. Measuring core body temperature and dim light melatonin onset

It is very important to know your chronotype as it will have an impact on your sleep. If your chronotype is night owl, you may face difficulty sleeping if you are trying to sleep at 10pm. If you are having difficulty in sleeping at night, I will advise to consult a Sleep physician who will not only determine your chronotype but also look into other potential causes of the sleep problem.

Recently a new way to profile chronotype shave been proposed. I feel this is will allow to include more people to be classified into different chronotypes as compared to traditional chronotyping. This chronotyping was proposed by Dr. Michael Breus. He proposes four types of chronotypes along with best timings for eating, exercising, coffee drinking and intimacy for each type-

  1. Bears:
  2. 50% people are bears.
  3. They are highly motivated, extroverted and bold people
  4. They are most productive from 9am-12pm
  5. Best time for them to sleep is 11pm-7am
  6. Best time for them to eat breakfast is 7:30am, lunch is 12:30pm and dinner 7:30pm
  7. Best time for the coffee to have maximum effect in morning is 9:30-11:30am
  8. Best time for them to run is 7:30am or 12:30pm
  9. Best time for intimacy is morning
  • Lion:
  • 15-20% people are Lions
  • They are the leaders, athletic type, morning people
  • They are most productive from 7am-12pm
  • Best time for them to sleep is 9pm-5am
  • Best time for them to eat breakfast is 6 am, lunch is 12 pm and dinner 6 pm
  • Best time for the coffee to have maximum effect in morning is 8-10 am
  • Best time for them to run is 5:30am
  • Best time for intimacy is morning
  • Wolves:
  • 15-20% people are Wolves
  • They are moody, introverted, creative and planners
  • They are most productive from 10am-5pm
  • Best time for them to sleep is 12am-8am
  • Best time for them to eat breakfast is 8 am, lunch is 1 pm and dinner 8 pm
  • Best time for the coffee to have maximum effect in morning is 12pm-2pm
  • Best time for them to run is 6pm
  • Best time for intimacy is morning
  • Dolphins
  • 10% of people are dolphins
  • They are very intelligent, strive for perfection, introverted
  • They are most productive throughout the day
  • Best time for them to sleep varies and often suffer from Insomnia complaint
  • Best time for them to eat breakfast is 8 am, lunch is 12 pm and dinner 7:30pm
  • Best time for the coffee to have maximum effect in morning is 8:30-10am
  • Best time for them to run is 7:30am
  • Best time for intimacy is morning

Paying attention to your chronotype will allow you to choose the right timings for everything in your life and be in sync with your circadian rhythms to sleep well and lead a healthy life.

Benefits of good night Sleep

Sleep has been retained by evolution during the process of natural selection in almost all species on earth. An adult human being spends 1/3rd of their life time sleeping. Sleep cannot be an evolutionary mistake given we spend 1/3rd of our lives sleeping.

Some of the most plausible theories of benefits of good night Sleep are-

  1. Energy conservation: Basal metabolic rate (BMR) during sleep is lower than the BMR of awake state. It has been proposed that Sleep reduces caloric use and restores energy stores of the body which have been depleted during wakefulness.8
  • Sleep restores brain energy stores: Studies have shown that in humans brain glucose consumption is approximately twice as high during waking as during slow wave sleep.9,10 This function is specific to NREM sleep as brain metabolic rate is higher during rapid eye movement sleep than during waking.11
  • Sleep helps to have good immune function: We all know from our personal experiences that whenever we fall ill, we sleep more as sleep aids in recovery from the disease. Studies have shown that sleep or sleep loss influence immune function.12,13

Stage N3 sleep has been shown to play an important role in immunologic memory by consolidating immune response to infection.14

Sleep enhances the hepatitis A virus (HAV)-specific T helper (Th) cell response to vaccination.15

Shorter sleep duration on the two nights before the vaccination predicted fewer antibodies 1 and 4 months later.16

This information is very important in today’s world suffering from Corona pandemic and the ongoing vaccination drive against Corona virus. American academy of Sleep Medicine (AASM) recommends following before/after immunization for Corona virus for a good night Sleep- (https://aasm.org/healthy-sleep-and-immune-response-to-covid-19-vaccination/)

  • Establish a bedtime and morning routine
  • Ensure the bedroom is a space for sleep
  • Set boundaries for blue light exposure
  • Limit alcohol, caffeine and large meals before bedtime 
  • Sleep on it: try to get good sleep on the night after vaccination

I will suggest in addition to above recommendations, to get good night sleep 2 nights before the vaccination as well.

  • Sleep helps to clear toxic metabolites from the brain: Study have shown that Short sleep duration (<6hrs) might be an early marker of Alzheimer disease.17 Alzheimer disease occurs due to accumulation of beta amyloid proteins in the brain.

There is a system called “Glymphatic system” in brain which helps to remove proteins linked to neurodegenerative diseases (β-amyloid, α-synuclein and tau).18 These proteins are present in the interstitial space surrounding cells of the brain. Glymphatic system consist of CSF recirculating through the brain interchanging with interstitial fluid (ISF) and helping to remove interstitial waste products and proteins, including β-amyloid.18 Glymphatic system activity is increased in Sleep as shown by Increased β-amyloid clearance during sleep.18

It has been shown that Slow wave sleep disruption increases beta amyloid levels acutely, and poorer sleep quality over several days increases tau protein levels.19

It looks like that maintaining sleep regularity, duration and quality may prevent onset of Alzheimer disease.

  • Sleep helps in memory consolidation: Memory formation involves three physiological processes- Encoding, Consolidation and Recall. Sleep has been characterized as a brain state optimizing memory consolidation.20 Consolidation occurs during Slow wave sleep and transfer them for integration into the long term memory.20 Ensuing REM sleep may stabilize transformed memories.20

My advice is do not lose sleep before any exam. Study in time and Sleep well on the night of the examination.

  • Sleep helps to regain our performance levels: We know that if we are tired and cannot perform a task, Sleep on it and try again next day. Studies have shown that after sleep deprivation performance is restored by sleep21 in a dose dependent manner.22
  • Sleep is good for your cardiovascular health: The function of our heart and blood vessels is controlled by Autonomic nervous system (ANS). ANS have two divisions- Sympathetic nervous system and parasympathetic nervous system.

Sympathetic nervous system is stimulatory and increases contractility of heart, heart rate, cardiac output, increases metabolic demand of heart, increases blood pressure and cause blood vessel constriction.

Parasympathetic nervous system slows heart rate, decreases- contractility, cardiac output, metabolic demand, blood pressure and causes blood vessel relaxation.

The balance between sympathetic and parasympathetic nervous system maintains cardiovascular health.

During NREM Sleep (compared to Wake) there is a decrease in sympathetic activity and increase in parasympathetic activity.

During REM Sleep (Compared to NREM Sleep), there is decrease in sympathetic activity and increase in parasympathetic activity. Although, transient increase in Sympathetic activity happens during phasic REM Sleep.

During sleep, systolic blood pressure (BP) decreases by 10% as compared to wake systolic BP.23 This is called “Dipping BP” phenomenon23 which is positively correlated with %age of Stage N3 and negatively with WASO.24 Absence of the Dipping BP phenomenon is a predictor of adverse cardiovascular events in nonmedicated hypertensive patients.23

It has been shown that lower %age of Stage N3 sleep increases the risk of developing hypertension in future in both men and women.25

This data shows that Sleep is good for your cardiovascular health and my suggestion is- “Sleep well for a healthy heart”.

  • Sleep improves athletic performance: It has been shown that there is a detrimental effect of sleep deprivation (a night or more without any sleep) and a beneficial effect of chronic sleep improvement (repeated exposure of strategies that improve sleep over weeks or months) on sports specific and physical performance.26-28 A consensus guideline29 has been published which suggest following for athletes Sleep to improve their performance-
  • Provide Sleep education for athletes
  • Screen athletes for Sleep problems
  • Encourage naps if sleep opportunity is not enough
  • Bank Sleep- Sleep extension prior to any major event

In this blog, I discussed about normal Sleep and its benefits. In my next blog I will discuss about how we can have a good night Sleep with 20tips on “Sleep hygiene” to help you Sleep better.

Until then “Sleep well. Sleep on time.”

References:

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2.         Wahl S, Engelhardt M, Schaupp P, Lappe C, Ivanov IV. The inner clock-Blue light sets the human rhythm. J Biophotonics. 2019;12(12):e201900102.

3.         Grønli J, Byrkjedal IK, Bjorvatn B, Nødtvedt Ø, Hamre B, Pallesen S. Reading from an iPad or from a book in bed: the impact on human sleep. A randomized controlled crossover trial. Sleep Med. 2016;21:86-92.

4.         Zerbini G, Kantermann T, Merrow M. Strategies to decrease social jetlag: Reducing evening blue light advances sleep and melatonin. Eur J Neurosci. 2020;51(12):2355-2366.

5.         Leger D, Richard JB, Collin O, Sauvet F, Faraut B. Napping and weekend catchup sleep do not fully compensate for high rates of sleep debt and short sleep at a population level (in a representative nationwide sample of 12,637 adults). Sleep Med. 2020;74:278-288.

6.         Ohayon M, Wickwire EM, Hirshkowitz M, et al. National Sleep Foundation’s sleep quality recommendations: first report. Sleep Health. 2017;3(1):6-19.

7.         Brindle RC, Yu L, Buysse DJ, Hall MH. Empirical derivation of cutoff values for the sleep health metric and its relationship to cardiometabolic morbidity: results from the Midlife in the United States (MIDUS) study. Sleep. 2019;42(9).

8.         Krueger JM, Frank MG, Wisor JP, Roy S. Sleep function: Toward elucidating an enigma. Sleep Med Rev. 2016;28:46-54.

9.         Kennedy C, Gillin JC, Mendelson W, et al. Local cerebral glucose utilization in non-rapid eye movement sleep. Nature. 1982;297(5864):325-327.

10.       Buchsbaum MS, Gillin JC, Wu J, et al. Regional cerebral glucose metabolic rate in human sleep assessed by positron emission tomography. Life Sciences. 1989;45(15):1349-1356.

11.       Braun AR, Balkin TJ, Wesenten NJ, et al. Regional cerebral blood flow throughout the sleep-wake cycle. An H2(15)O PET study. Brain. 1997;120(7):1173-1197.

12.       Imeri L, Opp MR. How (and why) the immune system makes us sleep. Nature Reviews Neuroscience. 2009;10(3):199-210.

13.       Besedovsky L, Lange T, Born J. Sleep and immune function. Pflügers Archiv – European Journal of Physiology. 2012;463(1):121-137.

14.       Besedovsky L, Lange T, Haack M. The Sleep-Immune Crosstalk in Health and Disease. Physiol Rev. 2019;99(3):1325-1380.

15.       Besedovsky L, Lange T, Born J. Sleep and immune function. Pflugers Arch. 2012;463(1):121-137.

16.       Prather AA, Pressman SD, Miller GE, Cohen S. Temporal Links Between Self-Reported Sleep and Antibody Responses to the Influenza Vaccine. International Journal of Behavioral Medicine. 2021;28(1):151-158.

17.       Leng Y, Ackley SF, Glymour MM, Yaffe K, Brenowitz WD. Genetic Risk of Alzheimer’s Disease and Sleep Duration in Non-Demented Elders. Ann Neurol. 2021;89(1):177-181.

18.       Xie L, Kang H, Xu Q, et al. Sleep drives metabolite clearance from the adult brain. Science. 2013;342(6156):373-377.

19.       Ju YS, Ooms SJ, Sutphen C, et al. Slow wave sleep disruption increases cerebrospinal fluid amyloid-β levels. Brain. 2017;140(8):2104-2111.

20.       Rasch B, Born J. About sleep’s role in memory. Physiological reviews. 2013;93(2):681-766.

21.       Rosa RR, Bonnet MH, Warm JS. Recovery of Performance During Sleep Following Sleep Deprivation. Psychophysiology. 1983;20(2):152-159.

22.       Banks S, Van Dongen HPA, Maislin G, Dinges DF. Neurobehavioral Dynamics Following Chronic Sleep Restriction: Dose-Response Effects of One Night for Recovery. Sleep. 2010;33(8):1013-1026.

23.       Bloomfield D, Park A. Night time blood pressure dip. World journal of cardiology. 2015;7(7):373-376.

24.       Loredo JS, Nelesen R, Ancoli-Israel S, Dimsdale JE. Sleep quality and blood pressure dipping in normal adults. Sleep. 2004;27(6):1097-1103.

25.       Javaheri S, Zhao YY, Punjabi NM, Quan SF, Gottlieb DJ, Redline S. Slow-Wave Sleep Is Associated With Incident Hypertension: The Sleep Heart Health Study. Sleep. 2018;41(1):zsx179.

26.       Fullagar HH, Skorski S, Duffield R, Hammes D, Coutts AJ, Meyer T. Sleep and athletic performance: the effects of sleep loss on exercise performance, and physiological and cognitive responses to exercise. Sports Med. 2015;45(2):161-186.

27.       Bonnar D, Bartel K, Kakoschke N, Lang C. Sleep Interventions Designed to Improve Athletic Performance and Recovery: A Systematic Review of Current Approaches. Sports Med. 2018;48(3):683-703.

28.       Vitale KC, Owens R, Hopkins SR, Malhotra A. Sleep Hygiene for Optimizing Recovery in Athletes: Review and Recommendations. Int J Sports Med. 2019;40(8):535-543.

29.       Walsh NP, Halson SL, Sargent C, et al. Sleep and the athlete: narrative review and 2021 expert consensus recommendations. Br J Sports Med. 2020.