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Sleep Architecture & Sleep Debt
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In one pass Sleep is not the brain switching off.
Educational content, not medical advice — consult a clinician.
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Chapter 1
How a night of sleep is staged
Sleep is not the brain switching off. Over a night it passes through several distinct states in a fixed order, and they are not spread evenly. The deepest kind of sleep — deep sleep, also called slow-wave sleep (N3) — is concentrated in the first half of the night. Rapid eye movement () sleep, where most dreaming happens, is concentrated in the second half. So if you lose two hours by waking early to an alarm, what you lose is mostly late-night REM; deep sleep is largely kept.
When you get sleepy is decided by two forces together. The longer you are awake, the higher your sleep pressure (Process S). An internal clock rises and falls on a roughly 24-hour cycle and decides what time you should feel sleepy (Process C). You fall asleep fast and stay asleep when both point to "time to sleep"; jet lag and all-nighters feel bad because the two have been pulled apart. To start with why you cannot fall asleep, see Insomnia.
When you get sleepy is decided by two forces together. The longer you are awake, the higher your sleep pressure (Process S). An internal clock rises and falls on a roughly 24-hour cycle and decides what time you should feel sleepy (Process C). You fall asleep fast and stay asleep when both point to "time to sleep"; jet lag and all-nighters feel bad because the two have been pulled apart. To start with why you cannot fall asleep, see Insomnia.
Mechanism · How a night moves through its cycles
A night passes through about 4-6 cycles of about 90 minutes each. Within each cycle the brain goes from light sleep to deep sleep, then into the dreaming stage.N1: the few-minute transition from waking to sleep; you are easily roused, and it takes up about 5% of the nightN2: the bulk of the night, about 45-55%. The EEG shows short bursts of rhythm called sleep spindles and large waveforms called K-complexes, both linked to stabilizing memoriesN3 (deep sleep, slow-wave sleep): the EEG turns into tall, slow waves (delta waves), and this is when you are hardest to wake (rapid eye movement sleep): the eyes dart, brain activity comes close to waking, yet the skeletal muscles are actively relaxed until they cannot move (muscle atonia); most dreaming happens here
What matters is not the list but the distribution. Deep sleep is concentrated in the first half of the night, highest in the first and second cycles after you fall asleep. REM is concentrated in the second half: the closer to dawn, the longer the REM segment in each cycle. Which part you lose on a short night is decided by this distribution.
Mechanism · How sleep pressure and the clock combine
The classic explanation of when you fall asleep and when you wake is the two-process model (proposed by Borbély in 1982 and reappraised by the original team in 2016): two independent processes decide it together.Process S is sleep pressure. The longer you are awake, the higher it climbs; once you are asleep it falls steadily, and deep sleep in the first half of the night is what discharges it. The build-up of adenosine in the brain is one of its molecular signals; for how caffeine blocks that signal, see Caffeine + L-Theanine.
Process C is the circadian rhythm: a rise and fall of alertness and sleepiness on a roughly 24-hour cycle, driven by the suprachiasmatic nucleus (, the body's master clock) in the hypothalamus, and independent of how long you have been awake. At the same sleep pressure, 6 am and 11 pm feel completely different.
In the model, the relationship works like a threshold that moves with the time of day. Process C draws an upper and a lower threshold line, and Process S rises and falls between them: when it reaches the upper line you fall asleep, and when it drops to the lower line you wake. So sleeping well needs enough built-up pressure and a clock that is in its sleep phase at the same time. The misery of jet lag, all-nighters and shift work comes down to the two being pulled apart and pointing in different directions.
This is a model, not an anatomy chart. It predicts well when people get sleepy, but which cells and molecules carry out each process in the brain is still being worked out.
Chapter 2
What deep sleep repairs
Deep sleep (N3, slow-wave sleep) is the stretch with the slowest brain waves, when you are hardest to wake, and it is concentrated in the first half of the night; after sleep loss, it is also the first thing the body makes up. Two jobs are fairly well tied to it. The pulses of growth hormone released at night mostly come during this stage, and heart rate and blood pressure fall to their daily low. Facts and events learned during the day are consolidated mainly during sleep rich in deep sleep (the Rasch & Born 2013 review). The third job people often mention — the brain being "washed" during sleep — comes from mouse experiments (Xie 2013) and has not been confirmed in people.
Deep sleep declining with age is normal (Ohayon 2004 pooled data from healthy people). Less deep sleep on its own is not a reason to think you are ill.
Deep sleep declining with age is normal (Ohayon 2004 pooled data from healthy people). Less deep sleep on its own is not a reason to think you are ill.
Mechanism · Growth hormone and memory consolidation
The body side. The pulsed release of growth hormone (GH) at night comes mostly in the deep sleep shortly after you fall asleep. At that time sympathetic tone drops to its daily low, and heart rate and blood pressure sink together. Growth hormone takes part in tissue repair and building-up (anabolic) metabolism, so deep sleep is often described as "repairing the body." But keep two sentences apart. That more growth hormone is released during deep sleep is something we can measure. That a little less deep sleep makes muscle and bone grow more slowly has no direct evidence in people. After a lot of exercise, the share of deep sleep often rises slightly.The memory side. Rasch & Born's 2013 review in Physiological Reviews pulls this research together: declarative memories — facts and events — are consolidated mainly during sleep rich in slow waves. The leading explanation is replay. In animal experiments, the hippocampus (the brain structure that holds new memories temporarily) replays the day's sequence of neural firing during deep sleep, gradually transferring the memory to the cortex. Human EEG studies also point this way, but exactly how the transfer happens is still being studied. In daily life: study, then sleep well, and you will remember it better than after an all-night cram. Procedural memories — movements and skills — are more closely tied to and N2.
Evidence · Xie 2013 is mice, not Alzheimer causation
Xie 2013, published in Science, found that in living mice, during natural sleep or anesthesia, the gaps between brain cells (the interstitial space) widened by about 60%. Convective exchange between cerebrospinal fluid and the fluid around brain cells sped up markedly, and the rate at which β-amyloid (the protein that builds up in Alzheimer's disease) was cleared rose with it. From this the authors proposed that sleep's restorative effect may come from clearing out potentially harmful metabolites that pile up while we are awake. The popular version is "the brain washes itself while you sleep."Read it with its limits. This is a mechanism study in mice. In the human brain, the anatomy and the measurement of this pathway — called the glymphatic system — are still being studied, and even in mice, the direction "sleep speeds up clearance" has been disputed by later animal work. So what it can support is that sleep may take part in clearing metabolic waste from the brain, a hypothesis worth serious study. What it cannot support is that sleeping badly will give you Alzheimer's disease; that would stretch a mouse mechanism into human cause and effect.
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Evidence · Less deep sleep with age is not disease
Ohayon 2004 is a that pooled overnight sleep recordings from 65 studies covering 3,577 healthy people aged 5-102. In adults, the share of slow-wave sleep, the share of and sleep efficiency all fell with age, while light sleep (N1 and N2) and time awake after falling asleep rose with age. After age 60, sleep efficiency was the only measure that kept falling clearly. That is the objective basis for "sleeping lighter as you get older": deep sleep starts declining slowly from early adulthood and more clearly from midlife.The same analysis also found that the more strictly a study screened its participants (excluding mental illness, chronic disease, alcohol or drug use, sleep apnea and so on), the smaller the age effects became, and some could not be detected at all. In other words, part of the sleep decline blamed on "getting older" actually comes from disease nobody has found.
So very little deep sleep on a report does not, by itself, mean much. Slow waves themselves get smaller with age, and under the scoring rules of a sleep study, some healthy older adults are credited with very little deep sleep. What deserves more attention is the daytime: still struggling to stay awake after enough hours in bed, loud snoring or waking up gasping, waking unrefreshed. These suggest that something else may be breaking up your sleep, and they are worth checking (see Obstructive Sleep Apnea).
On a short night, deep sleep is the best protected: it comes first in the night, and it is the first thing the body makes up after a loss. So a short night loses late-night REM first.
Chapter 3
REM sleep and what short nights cost
Rapid eye movement () sleep is the stretch in which the eyes dart, the EEG looks close to waking, and yet the skeletal muscles are relaxed until they cannot move. Most dreaming happens here. REM is concentrated in the second half of the night, and each segment gets longer as dawn approaches. So when an alarm cuts two hours off your sleep, what you lose is mostly the last one or two cycles, the ones richest in REM; the deep sleep of the first half is relatively kept.
People who sleep too little are often not too tired to walk. They are more irritable and react more strongly to bad news. Mood changes like these are common in people who are short of sleep, but how much comes from losing REM and how much from less sleep overall, human studies cannot yet separate. What is certain is that after REM has been taken away, it increases in the next sleep to make up for it: the body actively recovers it.
People who sleep too little are often not too tired to walk. They are more irritable and react more strongly to bad news. Mood changes like these are common in people who are short of sleep, but how much comes from losing REM and how much from less sleep overall, human studies cannot yet separate. What is certain is that after REM has been taken away, it increases in the next sleep to make up for it: the body actively recovers it.
Mechanism · What REM sleep is doing
During , the amygdala, the brain's emotional hub, is highly active, while noradrenaline, the chemical that keeps us alert and tense, is almost switched off. An influential hypothesis holds that the brain uses this low-stress chemical setting to reprocess the day's emotional memories, blunting the sting of an event while keeping the information. The evidence for this in people is still mixed, so for now it is one possible explanation.Procedural memory — the kind the body remembers how to do, such as cycling, an instrument or a sports skill — is consolidated in close connection with REM and also with the spindles of N2 (Rasch & Born 2013). Most dreams with a storyline and strong emotion happen in REM.
The loss of muscle tone during REM is a protection: you run in the dream while your body stays still in bed. When this mechanism fails, people act out their dreams physically, a condition called REM sleep behavior disorder. Unusual movements like these during sleep should be assessed by a doctor.
Mechanism · Which sleep a short night loses
Back to the distribution: deep sleep comes first, comes last. If you need 7 hours but sleep 5 because an alarm wakes you early, what gets cut is almost entirely the last one or two cycles, the ones richest in REM, while the deep sleep of the first half is relatively kept.After a stretch of REM deprivation, REM rebounds in recovery sleep: its share rises to make up the loss. This shows that the body actively recovers the REM it missed, rather than treating it as optional.
Follow the distribution one step further. If an alarm routinely wakes you early, what you mainly lose is REM, so a fixed wake time and leaving room each night for the last stretch of sleep fit this mechanism better than making it up at the weekend. That step is reasoning from the mechanism: no trial has directly compared which way of sleeping short does more harm.
Chapter 4
Sleep debt · can you repay it on weekends
Too little sleep on weekdays, sleeping until noon at the weekend: sleep debt is a useful metaphor, but sleep is not a bank account. After an acute shortfall of one or two nights, recovery sleep makes up most of it. A repeated, long-running shortfall cannot be settled in one weekend.
A randomized trial run in a laboratory (Depner 2019) tested weekend catch-up directly. Healthy young adults had only a 5-hour sleep opportunity each weekday night, could sleep as long as they liked at the weekend, and then went back to short sleep. In the group that caught up, insulin sensitivity still fell and body weight still rose once short sleep resumed. Weekend catch-up did not shield them from the metabolic effects of short sleep.
A randomized trial run in a laboratory (Depner 2019) tested weekend catch-up directly. Healthy young adults had only a 5-hour sleep opportunity each weekday night, could sleep as long as they liked at the weekend, and then went back to short sleep. In the group that caught up, insulin sensitivity still fell and body weight still rose once short sleep resumed. Weekend catch-up did not shield them from the metabolic effects of short sleep.
Evidence · Can weekend catch-up undo short sleep
For an acute shortfall of one or two nights, recovery sleep really does make up most of it: the body restores deep sleep first, and then rebounds. A chronic, repeated shortfall is a different matter.Depner 2019, published in Current Biology, is a in which participants lived in the laboratory. It split 36 healthy young adults into three groups: one with ample sleep opportunity every night (control), one with only 5 hours every night (continuous short sleep), and one with 5 weekdays of short sleep, 2 weekend days of sleeping as much as they liked, then 2 more short nights (weekend catch-up).
The continuous short-sleep group: whole-body insulin sensitivity fell about 13% from baselineThe weekend catch-up group: over the two weekend days they slept only about 1.1 hours more in total than at baseline. Once short sleep resumed, their body clock was pushed later, they ate more after dinner, and whole-body, liver and muscle insulin sensitivity fell about 9-27% from baselineBody weight: the catch-up group gained about 1.3 kg over the study, much like the continuous short-sleep group
The authors concluded that sleeping in at will at the weekend is not an effective way to prevent the metabolic disruption of repeated short sleep. Read its scope carefully: this was 36 healthy young adults over roughly two weeks, measuring short-term markers such as insulin sensitivity, food intake and body weight, not diabetes or heart disease themselves.
Mechanism · Why sleeping in makes Monday harder
Sleeping until noon at the weekend pushes your body clock (Process C) several hours later. On Sunday night you still want to sleep at 11, but your internal clock is stuck in a phase where you only get sleepy at 2 am. Getting up on Monday morning is like flying east again and going through another bout of jet lag. This is called social jet lag: your social schedule and your body clock no longer line up. Depner 2019 saw this in its weekend catch-up group too: once short sleep resumed, their circadian phase had shifted later.So weekend catch-up has three separate lines on the bill:
You can repay a little: catching up after acute sleep loss is worthwhile, so there is no need to swing to the other extreme of "catch-up is useless"You cannot clear the old debt: there is no evidence that a day or two of weekend catch-up fully erases long-running sleep loss, and in Depner's trial, the metabolic markers of the people who caught up did not return to where they startedThe way you repay has a cost: making it up with marathon weekend sleep pushes your body clock further out of line
The approach that fits the mechanism is not "owe now, repay later" but to avoid owing in the first place: sleep that is regular, sufficient, and anchored to a steady wake time.
Chapter 5
What disrupts sleep structure
Enough hours is not the same as sleeping well. Alcohol, caffeine, age and sleep apnea do not necessarily shorten the time you spend in bed, but all of them change the inner structure of sleep: less deep sleep, less , or a night chopped into pieces.
Alcohol helps you fall asleep faster and sleep more deeply in the first half of the night, but as it is metabolized you wake more often in the second half, and REM is pushed down (the Ebrahim 2013 review). Caffeine blocks adenosine, one of the signals of sleep pressure: you stop feeling sleepy for a while, but the sleepiness itself has not gone away. If you sleep a long time and are still tired, snore loudly, and can barely stay awake during the day, think of sleep apnea (see Obstructive Sleep Apnea).
Alcohol helps you fall asleep faster and sleep more deeply in the first half of the night, but as it is metabolized you wake more often in the second half, and REM is pushed down (the Ebrahim 2013 review). Caffeine blocks adenosine, one of the signals of sleep pressure: you stop feeling sleepy for a while, but the sleepiness itself has not gone away. If you sleep a long time and are still tired, snore loudly, and can barely stay awake during the day, think of sleep apnea (see Obstructive Sleep Apnea).
Mechanism · Why a nightcap breaks up the night
The Ebrahim 2013 review went through the studies of night-time sleep after drinking in healthy volunteers one by one (a qualitative review, with no pooled calculation), and its conclusions are fairly consistent:First half of the night: at every dose, alcohol makes you fall asleep faster and makes sleep in the first half more continuous; in most studies, deep sleep in the first half is also higher than usual. That is why it is so often used as a sleep aidSecond half of the night: as the alcohol is metabolized, sleep is disrupted and you wake more often: at every dose, the first REM period starts later; at moderate and high doses, most studies find a lower share of REM over the whole night
The net effect: you fall asleep, but the second half of the night is more broken, and you wake unrefreshed. The extra deep sleep early in the night is real, but it is paid for with a broken second half and less REM. As a sleeping pill, alcohol is a poor trade.
Mechanism · Caffeine blocks the signal, not the need
Caffeine looks enough like adenosine to get to adenosine's receptors first and occupy them. Adenosine is one of the molecular signals of sleep pressure (Process S); for the full pharmacology, see Caffeine + L-Theanine. So caffeine does not remove tiredness. It only stops the brain, for a while, from receiving the signal "you are already very tired."Its half-life averages about 4-5 hours, with large differences between people: a cup at 3 pm still leaves a meaningful amount in your body at bedtime. Even if you fall asleep as usual, it lowers the share of deep sleep and makes you wake more during the night. Moving your last coffee of the day earlier (for most people, stopping by early afternoon) is the cheapest way to improve sleep structure.
Clinical · Lighter with age versus chopped up
A falling share of deep sleep and more waking at night with age are real physiological changes (Ohayon 2004), so there is no need to read less deep sleep as illness the moment you see it. Whether to get checked depends not on the deep-sleep percentage on a report but on whether several things show up together: badly fragmented sleep, waking unrefreshed, and clear effects on your energy and work during the day. When they come together, it has gone beyond normal aging and is worth a doctor's workup (see Obstructive Sleep Apnea; for trouble falling asleep, see Insomnia).Obstructive sleep apnea is a different kind of problem. After you fall asleep, the airway at the back of the throat collapses again and again, breathing stops each time, and the brain is briefly woken (micro-arousals). Sleep is chopped into pieces, and both deep sleep and are hard to hold. Sleeping 8 hours and still being tired, snoring loudly, barely staying awake by day: this is not something "poor sleep quality" covers. It is a medical problem that needs a sleep study to diagnose, and the most common treatment is a machine worn during sleep that keeps the airway open with steady air pressure (continuous positive airway pressure, ).
None of these four necessarily shortens your time in bed, but all of them change the structure of your sleep. The answer to "why am I still tired when I slept enough" is often in the structure, not the duration.
Chapter 6
Fixed wake time, enough hours
Protecting the structure of sleep pays off more than simply piling up hours. The easiest move is a fixed wake time, weekends included, which steadies your body clock. Adults should sleep the amount they need, judged by how they function during the day; the American Academy of Sleep Medicine's consensus is at least 7 hours a night on a regular basis. Do not let an alarm yank you out of your last cycle, and do not drink before bed.
If you fall asleep but wake unrefreshed, look first among the disruptors: alcohol, caffeine, sleep apnea. If you cannot fall asleep at all, the first choice is cognitive behavioral therapy for insomnia (), which the American Academy of Sleep Medicine's 2021 guideline strongly recommends (see Insomnia). For persistent, severe sleep problems, see a doctor.
If you fall asleep but wake unrefreshed, look first among the disruptors: alcohol, caffeine, sleep apnea. If you cannot fall asleep at all, the first choice is cognitive behavioral therapy for insomnia (), which the American Academy of Sleep Medicine's 2021 guideline strongly recommends (see Insomnia). For persistent, severe sleep problems, see a doctor.
In practice · Fix your wake-up time first
A fixed wake time (weekends included) is the most powerful way to steady Process C: it lines up sleep pressure with the body clock, so you naturally feel sleepy when it is time. Rather than agonizing over "I have to get a full 8 hours tonight," pin down your wake time first.The joint consensus of the American Academy of Sleep Medicine (AASM) and the Sleep Research Society (Watson 2015) recommends that adults regularly sleep 7 hours or more a night. But how much you need varies from person to person. The yardstick is how you function during the day (attention, mood, error rate), not fixating on one number; for whether short sleep with a good day counts as insomnia, see Insomnia.
Protect late-night : do not let an alarm yank you out of the last REM cycle, and do not drink before bedProtect deep sleep: stop caffeine by early afternoon, at least 6 hours before bed; keep the bedroom cool, dark and quiet; exercise regularly. Daytime or evening exercise are both fine; what to avoid is hard exercise that ends right before bedtimeUse light to set the clock: morning light resets Process C; in the evening, dim the lights and screens so the suprachiasmatic nucleus () gets the signal that it is time to sleep
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Myth · Catch-up sleep, sleep scores, and a nightcap
"Weekend catch-up clears the debt." It does not. In the Depner 2019 trial, the people who caught up still lost insulin sensitivity once short sleep resumed, so do not count on the weekend to rescue you."More deep sleep is always better, so push it up with a device or a supplement." The share of deep sleep is regulated by the body itself, and healthy people have no need to push it. Wearables estimate sleep stages with considerable error, so do not worry over one number on a wristband.
"A drink before bed helps you sleep." It does help you fall asleep faster, but the second half of the night is more broken and is reduced, so you wake less refreshed.
"If you cannot sleep, just stay in bed longer." Lying awake in bed only strengthens the link "bed means awake"; stimulus control, part of cognitive behavioral therapy, is designed to break exactly that link (see Insomnia).
In practice · Where to look when sleep goes wrong
This story explains why sleep works the way it does. For a specific problem, find the matching story by symptom:Cannot fall or stay asleep: how insomnia is judged, the first-choice treatment, cognitive behavioral therapy for insomnia (, strongly recommended by the American Academy of Sleep Medicine's 2021 guideline, Edinger 2021), and the risks of sleeping pills; see InsomniaPulled an all-nighter: All-Nighter covers a single night of total sleep loss, when what gets cut is exactly the deep sleep and described hereThat afternoon coffee: how caffeine blocks the sleep-pressure signal; see Caffeine + L-TheanineThinking of taking melatonin: melatonin is a timing signal for the body clock (Process C), not a sleeping pillShift work: Shift Work covers what happens when sleep pressure and the body clock are pulled apart for yearsStressed and sleeping lightly: Chronic Stress covers how long-term stress and sleep drag each other downLoud snoring, extreme daytime sleepiness: the common medical cause that chops sleep into pieces; see Obstructive Sleep Apnea
Sleep is not a duration number but a layered structure: more deep sleep in the first half of the night, more REM in the second. Protecting that structure — regular, sufficient sleep, less alcohol, an early caffeine cutoff — is closer to the mechanism than chasing any deep-sleep score. This site does not replace a physician: persistent severe sleep problems, loud snoring plus extreme daytime sleepiness, or abnormal behaviors during sleep warrant medical evaluation.
References · 9
- Borbély, A. A., Daan, S., Wirz-Justice, A., & Deboer, T. (2016). The two-process model of sleep regulation: a reappraisal. Journal of Sleep Research, 25(2), 131-143. 10.1111/jsr.12371
- Watson, N. F., Badr, M. S., Belenky, G., Bliwise, D. L., Buxton, O. M., Buysse, D., et al. (2015). Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. Journal of Clinical Sleep Medicine, 11(6), 591-592. 10.5664/jcsm.4758
- Borbély, A. A. (1982). A two process model of sleep regulation. Human Neurobiology, 1(3), 195–204. pubmed.ncbi.nlm.nih.gov/7185792
- Rasch, B., & Born, J. (2013). About sleep's role in memory. Physiological Reviews, 93(2), 681-766. 10.1152/physrev.00032.2012
- Xie, L., Kang, H., Xu, Q., Chen, M. J., Liao, Y., Thiyagarajan, M., O'Donnell, J., Christensen, D. J., Nicholson, C., Iliff, J. J., Takano, T., Deane, R., & Nedergaard, M. (2013). Sleep drives metabolite clearance from the adult brain. Science, 342(6156), 373-377. 10.1126/science.1241224
- Ohayon, M. M., Carskadon, M. A., Guilleminault, C., & Vitiello, M. V. (2004). Meta-analysis of quantitative sleep parameters from childhood to old age in healthy individuals: developing normative sleep values across the human lifespan. Sleep, 27(7), 1255-1273. 65 studies, 3,577 healthy participants aged 5-102, published 1960-2003. In adults, total sleep time, sleep efficiency, % slow-wave sleep, % REM and REM latency decreased with age while sleep latency, % stage 1, % stage 2 and wake after sleep onset increased; only sleep efficiency continued to decrease significantly after age 60. Effect sizes depended on how strictly participants were screened for mental and organic disease, drug or alcohol use and sleep disorders - screening diminished or even masked the age associations (abstract, PMID 15586779). 10.1093/sleep/27.7.1255
- Depner, C. M., Melanson, E. L., Eckel, R. H., Snell-Bergeon, J. K., Perreault, L., Bergman, B. C., Higgins, J. A., Guerin, M. K., Stothard, E. R., Morton, S. J., & Wright, K. P. (2019). Ad libitum weekend recovery sleep fails to prevent metabolic dysregulation during a repeating pattern of insufficient sleep and weekend recovery sleep. Current Biology, 29(6), 957-967. 36 healthy young adults randomized to 9-h sleep (n = 8), continuous 5-h restriction (SR, n = 14) or restriction with weekend recovery followed by 2 more restricted nights (WR, n = 14). Weekend recovery added only ~1.1 h of sleep in total over baseline, and afterwards circadian phase was delayed. Whole-body insulin sensitivity fell ~13% in SR; in WR, whole-body, hepatic and muscle insulin sensitivity fell ~9-27% during the recurrent restriction. Body weight rose 1.4 ± 0.5 kg in SR and 1.3 ± 0.4 kg in WR by day 13 (SR vs WR P = 0.91); controls +1.0 kg, not significant (abstract, PMID 30827911; full text, PMC12798825). 10.1016/j.cub.2019.01.069
- Ebrahim, I. O., Shapiro, C. M., Williams, A. J., & Fenwick, P. B. (2013). Alcohol and sleep I: effects on normal sleep. Alcoholism: Clinical and Experimental Research, 37(4), 539-549. Qualitative review of studies in healthy volunteers. At all doses alcohol shortens sleep onset latency, consolidates the first half of sleep and disrupts the second half; a delayed first REM period at all doses is its most recognizable REM effect. Total-night REM % falls in most studies at moderate and high doses, with no clear trend at low doses. Most studies show more slow-wave sleep in the first half of the night; total-night slow-wave sleep rises at high doses (abstract, PMID 23347102). 10.1111/acer.12006
- Edinger, J. D., Arnedt, J. T., Bertisch, S. M., et al. (2021). Behavioral and psychological treatments for chronic insomnia disorder in adults: an American Academy of Sleep Medicine clinical practice guideline. Journal of Clinical Sleep Medicine, 17(2), 255-262. 10.5664/jcsm.8986