National Self Care Week: Why Sleep Health Matters More Than You Think

Written and reviewed by Dr Jean-Marc Sobczyk, Integrative and Longevity Doctor at Hooke London.

Despite its importance, most people tend to treat sleep as the thing that happens once everything else is done. We understand that with our busy lives, sleep is treated as a luxury, but science suggests it is a necessity.

This National Self Care Week, we are looking beyond the evening routine to ask a bigger question: why does sleep health matter so much? We are delighted to work on this article alongside Hooke London, who have gathered the science behind a good night's rest.

From Dr Jean-Marc Sobczyk, Integrative and Longevity Doctor at Hooke London

"I have been a doctor for 25 years, and sleep is still the one thing I ask every patient about, because nothing else I do works properly without it. Gut repair, hormone balance, immune recovery, mood, memory: all of it is quietly rebuilt in the hours you spend asleep. Most of the people who come to see me have been treating sleep as the thing they can borrow from. The body keeps better accounts than we do."

While we sleep, our brains are far from idle. Moving through repeating cycles of light and deep sleep, each stage plays a part in how we learn and remember. During deep sleep and REM sleep (Rapid Eye Movement) the brain files away new information, strengthening the memories that matter and letting go of those that do not. It is like an overnight tidy so that we can start the next day with a clear head.

From Dr Jean-Marc

"That overnight tidy is a real, measurable process. Through the night we move through four or five sleep cycles of roughly 90 minutes each. Early in the night the cycles are rich in deep, slow-wave sleep; later they are rich in REM, the dreaming stage. During deep sleep a part of the brain called the hippocampus, which acts as the day's in-tray, replays what you have learned and moves it into long-term storage [1].

The study I quote most often is simple. People who learned a finger-tapping pattern in the evening were about 20% faster at it the next morning, after a night's sleep. People who learned it in the morning and were tested that evening, with the same hours in between but no sleep, had barely improved [2].

Deep sleep also seems to be when the brain cleans itself. In sleeping volunteers, each slow brain wave is followed by a wave of clear fluid washing through the brain [3]. In mice, that fluid carries away the waste that builds up during the day, including amyloid, the protein linked to Alzheimer's disease [4]. That part is likely to apply to humans, but it has not yet been replicated in human studies. What we do have in people is this: after one night without sleep, a tracer dye cleared more slowly from the brain, and the following night's sleep did not make up for it [5].

On focus, the finding that worries me most is this. Healthy adults were limited to six hours of sleep a night for two weeks. By the end, they performed as badly on attention tests as people who had been kept awake for two full nights. Asked how sleepy they felt, they said "a bit" [6]. Six hours does not feel dangerous. That is exactly what makes it dangerous."

Many of us know how poor sleep feels and as a result the next day we experience our patience running short, small frustrations feel more significant and everything seems to take much more effort. Whilst we put it down to tiredness, the quality of sleep the night before has played a much larger role in how our brain has processed emotions. Consistently short or broken sleep is linked with lower mood and greater stress, but a good night's sleep helps us meet the day with more resilience and a fresher perspective. During our day we can adopt self-care routines such as clean eating and skincare, but sleep is one of the most important forms of self-care there is.

From Dr Jean-Marc

"Brain scans agree with that description. After about 35 hours without sleep, the amygdala, the brain's alarm centre, reacted over 60% more strongly to upsetting images, while the part of the brain that normally keeps the alarm in proportion had lost its grip [7]. Fifty years of experiments say the same: shorten sleep and good mood drops, while anxiety and irritability rise [8].

The encouraging part is that it works the other way too. Researchers pooled 65 clinical trials, over 8,600 people, in which sleep was improved and mood was then measured. Better sleep meant better mental health, with the clearest gains for depression and anxiety, and the more sleep improved, the more mood improved [9]. Sleep is one of the few levers on mood that a person can pull themselves. For readers who want the source, the 2021 review in Sleep Medicine Reviews is free to read online [9]."

The benefits reach beyond the brain. During rest, the body carries out essential repair work, supports the immune system and helps regulate hormones that influence appetite and energy. Regular, good quality sleep is linked to better heart health and a lower risk of a number of chronic conditions.

From Dr Jean-Marc

"Three findings bring that to life.

Immunity. Healthy adults had their sleep tracked for a week and were then exposed to a cold virus. Those sleeping under six hours a night were about four times more likely to come down with a cold than those sleeping over seven [10]. Sleep also shapes how well vaccines work, and long-term short sleep is linked to the low-level inflammation that sits underneath most diseases of ageing [11].

Appetite and metabolism. When young men were limited to four hours of sleep for just two nights, the hormone that signals fullness (leptin) fell by about 18%, the hormone that drives hunger (ghrelin) rose by about 28%, and their cravings for sweet and starchy food went up by a third or more [12]. In another study, overweight adults on the same diet lost the same weight whether they slept 5.5 or 8.5 hours, but the short sleepers lost far less of it as fat and far more as muscle [13]. Growth hormone, which drives overnight repair, is released mainly in deep sleep, and both fall away sharply between our twenties and our forties [14].

Heart health. Looking at 15 long-term studies of nearly half a million people, those who habitually slept short had a 48% higher risk of developing or dying from coronary heart disease over the following years [15]. That is an association rather than proof of cause, but it is a consistent one."

Reaction times, judgement and decision making all suffer when we are short of rest so for many people, particularly in high-risk professions, sleep is a safety matter. This is also true for those who work long or irregular hours such as hospitality teams, shift workers, and superyacht crew who often balance demanding schedules with the need to stay sharp.

Protecting sleep is not about indulgence, it is about supporting our bodies to do their best and stay focused and safe in the work we do.

From Dr Jean-Marc

"After 17 to 19 hours awake, reaction time and judgement are as impaired as if you had a blood alcohol level of 0.05%, which is over the drink-drive limit in most of Europe. Push through the night and you reach the equivalent of 0.10% [16,17]. Nobody would let a crew member take the helm, or a housekeeper handle a guest's belongings, with a drink and a half in them. We allow it without sleep every day.

Tiredness does not harm every kind of thinking equally. Familiar, routine tasks hold up surprisingly well. What falls apart is the ability to deal with the unexpected: noticing the plan has stopped working, changing it, ignoring a distraction, communicating under pressure [18]. For an interior designer, that is the detail missed on the final walk-through. For a stewardess on a charter, it is the guest request that lands badly. For a watchkeeper, it is the moment an incident becomes an accident.

The maritime research is sobering. In a European project called HORIZON, ship's officers worked a week of realistic watches in full simulators while their brain activity was recorded. Around one in five fell asleep at some point during the midnight-to-six watch, and the six hours on, six hours off pattern produced the most lost sleep [19]. The International Maritime Organization's own guidance says that meeting the rest-hour rules is not the same as managing fatigue [20]. The rules are the floor, not the ceiling."

Although the amount of hours you get each night is important, good sleep is more than that. Most adults need roughly seven to nine hours a night but quality and consistency count too. How easily we fall asleep, how uninterrupted our sleep is, and whether we go to bed and wake at similar times each day play a big role too.

From Dr Jean-Marc

"It is the National Sleep Foundation's range for adults aged 18 to 64, with seven to eight for those over 65 [21]. The two main sleep medicine societies put it slightly differently: seven hours or more, with six or fewer judged not enough for health or safety [22]. Either way, six is the number to worry about.

Quality has a definition too. An expert panel settled on four signs of a good night: you fall asleep within about half an hour, you wake no more than once, you spend little time awake after that, and you are asleep for at least 85% of the time you are in bed [23].

And consistency may matter most of all. In a study of over 60,000 people wearing activity trackers, how regular their sleep timing was predicted how long they lived more strongly than how many hours they slept. The most regular sleepers had a 20 to 48% lower risk of dying over the study period than the least regular [24]. Seven hours starting at a different time every night is not the same as seven hours starting at eleven."

The good news is that small changes can make a real difference. Some gentle places to start:

• Keep to a rhythm. Going to bed and waking at similar times, even at weekends, helps the body clock settle.
• Welcome the daylight. Natural light in the morning supports the body's sense of when it is time to be awake and when it is time to rest.
• Ease into the evening. Dimming lights and putting screens aside helps the mind unwind. For more ideas, see our Evening Wind Down guide.
• Create a calm, cool bedroom. A quiet, dark, comfortably cool room is widely recommended for better sleep.

From Dr Jean-Marc

"All four of those are well founded. If I had to choose one, it would be the fixed wake time, which is the habit behind the regularity finding above [24]. Morning light is the signal that sets the body clock, and laboratory studies show that bright light soon after waking shifts the clock earlier, making it easier to fall asleep that night [25]. On screens, reading on a backlit tablet rather than a printed book delayed the sleep hormone melatonin by over an hour and left people groggier the next morning [26]. On the bedroom, the best study tracked older adults over nearly 11,000 nights and found sleep was best between 20 and 25°C, with a lot of variation between people [27]. Younger adults often prefer cooler, and natural, breathable bedding helps for the same reason: it lets the body release heat rather than trap it.

Four more that have been tested:

• Move your last coffee earlier. A large coffee's worth of caffeine taken six hours before bed cut sleep by over an hour in a controlled trial. The participants did not notice [28]. For most people, nothing with caffeine after early afternoon.
• A warm bath or shower one to two hours before bed. A review of 17 studies found warm water, for as little as ten minutes, helped people fall asleep faster. Warming the skin lets the core cool, and a cooling core is the body's signal that night has begun [29].
• Be honest about alcohol. It helps you fall asleep, then breaks up the second half of the night [30].
• If you work watches, nap on purpose. A planned rest of about 26 minutes made long-haul pilots measurably more alert through landing [31]. A short nap before a night watch is good fatigue management.

And if sleep has been broken for months, the treatment with the strongest evidence is a structured talking therapy called CBT-I (cognitive behavioural therapy for insomnia). Sleep medicine guidelines give it their strongest recommendation and specifically say that sleep hygiene tips on their own are not a treatment [32]. Ask your GP about it before you ask for a tablet."

Sleep is easy to overlook, but it is one of the foundations of good health. This National Self Care Week, we hope you will give it the attention it deserves. A good night's sleep may be the quietest form of self-care, and yet one of the most powerful.

From Dr Jean-Marc

"Everything else we call self-care is built on top of sleep. Protect the hours, protect the timing, and make the bedroom cool, dark and comfortable enough that your body can do the rest."

This article was written and reviewed by Dr Jean-Marc Sobczyk, Integrative and Longevity Doctor at Hooke London. Dr Sobczyk has 25 years of clinical experience, and his practice focuses on gut health, hormones, genomics and environmental medicine, with sleep as the foundation of all of it.

This article is intended to share general information about sleep health and is not medical advice. Anyone who is concerned about their sleep should speak with their GP or a qualified healthcare professional.

1.        Rasch B, Born J. About sleep's role in memory. Physiological Reviews. 2013;93(2):681-766.
2.        Walker MP, et al. Practice with sleep makes perfect. Neuron. 2002;35(1):205-211.
3.        Fultz NE, et al. Coupled electrophysiological, hemodynamic, and cerebrospinal fluid oscillations in human sleep. Science. 2019;366:628-631.
4.        Xie L, et al. Sleep drives metabolite clearance from the adult brain. Science. 2013;342:373-377. (Mouse study.)
5.        Eide PK, et al. Sleep deprivation impairs molecular clearance from the human brain. Brain. 2021;144(3):863-874.
6.        Van Dongen HP, et al. The cumulative cost of additional wakefulness. Sleep. 2003;26(2):117-126.
7.        Yoo SS, et al. The human emotional brain without sleep. Current Biology. 2007;17(20):R877-R878.
8.        Palmer CA, et al. Sleep loss and emotion: a systematic review and meta-analysis. Psychological Bulletin. 2024;150(4):440-463.
9.        Scott AJ, et al. Improving sleep quality leads to better mental health: a meta-analysis of randomised controlled trials. Sleep Medicine Reviews. 2021;60:101556. doi:10.1016/j.smrv.2021.101556 (open access).
10.     Prather AA, et al. Behaviorally assessed sleep and susceptibility to the common cold. Sleep. 2015;38(9):1353-1359.
11.     Besedovsky L, et al. The sleep-immune crosstalk in health and disease. Physiological Reviews. 2019;99(3):1325-1380.
12.     Spiegel K, et al. Brief communication: sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Annals of Internal Medicine. 2004;141(11):846-850.
13.     Nedeltcheva AV, et al. Insufficient sleep undermines dietary efforts to reduce adiposity. Annals of Internal Medicine. 2010;153(7):435-441.
14.     Van Cauter E, et al. Age-related changes in slow wave sleep and REM sleep and relationship with growth hormone and cortisol levels in healthy men. JAMA. 2000;284(7):861-868.
15.     Cappuccio FP, et al. Sleep duration predicts cardiovascular outcomes: a systematic review and meta-analysis of prospective studies. European Heart Journal. 2011;32(12):1484-1492.
16.     Dawson D, Reid K. Fatigue, alcohol and performance impairment. Nature. 1997;388:235.
17.     Williamson AM, Feyer AM. Moderate sleep deprivation produces impairments equivalent to legally prescribed levels of alcohol intoxication. Occupational and Environmental Medicine. 2000;57(10):649-655.
18.     Harrison Y, Horne JA. The impact of sleep deprivation on decision making: a review. Journal of Experimental Psychology: Applied. 2000;6(3):236-249.
19.     Project HORIZON Consortium. Project HORIZON: a wake-up call. Final report, 2012.
20.     International Maritime Organization. Guidelines on fatigue. MSC.1/Circ.1598. 2019.
21.     Hirshkowitz M, et al. National Sleep Foundation's sleep time duration recommendations: methodology and results summary. Sleep Health. 2015;1(1):40-43.
22.     Watson NF, et al. Recommended amount of sleep for a healthy adult: joint consensus statement of the AASM and SRS. Sleep. 2015;38(6):843-844.
23.     Ohayon M, et al. National Sleep Foundation's sleep quality recommendations: first report. Sleep Health. 2017;3(1):6-19.
24.     Windred DP, et al. Sleep regularity is a stronger predictor of mortality risk than sleep duration. Sleep. 2024;47(1):zsad253.
25.     Revell VL, et al. Advancing human circadian rhythms with afternoon melatonin and morning intermittent bright light. Journal of Clinical Endocrinology and Metabolism. 2006;91(1):54-59.
26.     Chang AM, et al. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. PNAS. 2015;112(4):1232-1237.
27.     Baniassadi A, et al. Nighttime ambient temperature and sleep in community-dwelling older adults. Science of the Total Environment. 2023;899:165623.
28.     Drake C, et al. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine. 2013;9(11):1195-1200.
29.     Haghayegh S, et al. Before-bedtime passive body heating by warm shower or bath to improve sleep: a systematic review and meta-analysis. Sleep Medicine Reviews. 2019;46:124-135.
30.     Ebrahim IO, et al. Alcohol and sleep I: effects on normal sleep. Alcoholism: Clinical and Experimental Research. 2013;37(4):539-549.
31.     Rosekind MR, et al. Alertness management: strategic naps in operational settings. Journal of Sleep Research. 1995;4(S2):62-66.
32.     Edinger JD, et al. Behavioral and psychological treatments for chronic insomnia disorder in adults: an AASM clinical practice guideline. Journal of Clinical Sleep Medicine. 2021;17(2):255-262.