What does an all-nighter do to your brain?
After 17 hours without sleep, you react as poorly as with 0.5 g of alcohol per liter of blood, and after 24 hours, as with 1 g, a BAC of 0.10% (NIOSH; Williamson and Feyer, 2000). The brain builds up adenosine, switches off for moments in microsleeps, and its prefrontal cortex, the part that judges and holds back, slows down.
Simplified diagram, not to scale. Dotted curves are estimates based on the cited studies; the figures in the notes are measured.
What does an all-nighter do to your brain?
The brain seen from the side, during a night without sleep. Choose a situation, then tap a label on the drawing to find out what it is.
Sources: adenosine (Porkka-Heiskanen, Science, 1997; Elmenhorst, J Neurosci, 2007 and PNAS, 2017); comparison with alcohol (NIOSH; Williamson and Feyer, Occup Environ Med, 2000); microsleeps and thalamus (Poudel, Hum Brain Mapp, 2014); prefrontal cortex (Thomas, J Sleep Res, 2000); caffeine (Fredholm, 1999; McLellan, 2016); nap (Brooks and Lack, Sleep, 2006). Drawing not to scale; amount of adenosine and alertness curve: estimates.
Keyboard: 1 to 3 situations, Space pause, L slow motion, R start over, ← → previous or next step.
Frequently asked questions about all-nighters
How long does it take to recover from an all-nighter?
After a single all-nighter, one good night of sleep brings back most of your alertness. In 15 men kept awake for 52 hours, a 14-hour recovery night brought adenosine receptors, the fatigue molecule's landing sites, back to normal (Elmenhorst, 2017). After several short nights, it takes longer: after 7 nights of 5 hours, 3 nights of 8 hours were not enough to get reaction speed fully back (Belenky, 2003).
Is it safe to drive after an all-nighter?
It is better not to drive after an all-nighter: after 24 hours without sleep, you react as if you had 1 g of alcohol per liter of blood, a BAC of 0.10%, above the US legal limit of 0.08% (NIOSH). After just 17 hours awake, test results are as poor as at 0.5 g/L, with responses up to 50% slower (Williamson and Feyer, 2000). The brain can also switch off for 0.5 to 15 seconds without you choosing to: these are microsleeps (Poudel, 2014).
Does coffee help after an all-nighter?
Coffee helps you stay alert, but it masks fatigue without erasing it. From about 40 to 300 mg, caffeine improves alertness, attention and reaction time, much less memory and reasoning (McLellan, 2016). It takes adenosine's place on its receptors (Fredholm, 1999), and half of it stays in the blood for about 5 hours (IOM, 2001): an afternoon coffee can disturb your recovery night.
Why am I hungry after an all-nighter?
You are hungrier after an all-nighter because ghrelin, the hunger hormone, goes up. In 9 men, it was 22% higher than after a normal night, and hunger was rated 3.9 versus 1.7 (Schmid, 2008). In 12 men, a single night cut to 4 hours led them to eat 559 more calories the next day (Brondel, 2010). The page on hunger explains why it comes back at the same times.
Should I take a nap after an all-nighter?
Yes, a short nap helps, as long as you keep it under 20 to 30 minutes. In 24 young adults who had slept little, a 10-minute nap improved alertness right away and for 155 minutes; after 30 minutes, people first woke up groggy (Brooks and Lack, 2006). A 200 mg coffee taken just before a 20-minute nap worked even better for the following hour (Hayashi, 2003).
True or false?
After an all-nighter, you drive as badly as after drinking.
True. After 24 hours without sleep, you react as if you had 1 g of alcohol per liter of blood (a BAC of 0.10%), and after just 17 hours as if you had 0.5 g/L (NIOSH; Williamson and Feyer, 2000).
A good cup of coffee can replace a night of sleep.
False. Caffeine sits on adenosine receptors and masks fatigue without erasing it (Fredholm, 1999). When it wears off, the built-up fatigue comes back; only sleep clears adenosine (Elmenhorst, 2017).
The longer the nap, the better you feel when you wake up.
False. A 10-minute nap restored alertness right away; after 30 minutes, people first woke up groggy (Brooks and Lack, 2006).
This page as text
The same information as the charts, to read without animation: for each chart, the values at the main moments, then the notes with their level of evidence.
After how many hours without sleep are you like drunk?
After 17 hours awake, like 0.5 g of alcohol per liter of blood; after 24 hours, like 1 g. Sleep pressure keeps rising; the body clock offsets it during the day, but no longer at the end of the night. Estimated curves, as relative levels.
| Hours awake or time of day the next day | Sleep pressure (adenosine) (dotted) | Wake drive from the body clock (dotted) | Attention lapses (dotted) | What happens |
|---|---|---|---|---|
| 0 h | 5 | 45 | 2 | awake (7 a.m.) |
| 8 h | 30 | 55 | 2 | awake (3 p.m.) |
| 16 h | 55 | 66 | 6 | awake (11 p.m.) |
| 24 h | 75 | 30 | 58 | awake (7 a.m., the next day) |
| 32 h | 88 | 55 | 57 | awake (3 p.m., the next day) |
| 40 h | 96 | 70 | 85 | awake (11 p.m., the next day) |
Key points
- The first 16 hours (Up to 16 h awake, Shown in humans)
In 48 adults, attention lapses stayed rare up to about 16 hours awake, then rose almost in a straight line with each extra hour (Van Dongen, 2003). Source: Van Dongen et al., "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 - Adenosine builds up (Up to 24 h awake, Seen in animals)
In cats, adenosine rises in the brain during prolonged wakefulness and pushes toward sleep; it falls again during sleep (Porkka-Heiskanen, 1997). Source: Porkka-Heiskanen et al., "Adenosine: a mediator of the sleep-inducing effects of prolonged wakefulness", Science, 1997 - 17 hours: like 0.5 g/L (From 16 to 24 h awake, Shown in humans)
In 39 people, after 17 to 19 hours without sleep, test results were as bad as or worse than with a BAC of 0.05%, or 0.5 g/L, and responses were up to 50% slower. Source: Williamson and Feyer, "Moderate sleep deprivation produces impairments in cognitive and motor performance equivalent to legally prescribed levels of alcohol intoxication", Occup Environ Med, 2000 - Erratic responses (After 18 h awake, Shown in humans)
During 88 hours of sleep deprivation, in 13 people, reaction times became very irregular after 18 hours awake: normal responses alternate with blanks (Doran, 2001). Source: Doran, Van Dongen and Dinges, "Sustained attention performance during sleep deprivation: evidence of state instability", Arch Ital Biol, 2001 - The worst time: the end of the night (From 20 to 24 h awake, Shown in humans)
Alertness depends on two forces: sleep pressure, which rises with hours awake, and the body clock, which pushes toward wakefulness during the day and not at all at the end of the night (Borbély, 1982). The low point falls around 3 to 6 a.m. (to be checked). Source: Borbély, "A two process model of sleep regulation", Hum Neurobiol, 1982 - 24 hours: like 1 g/L (After 24 h awake, Shown in humans)
NIOSH, the US occupational health institute, sums it up: 17 hours awake equal a BAC of 0.05%, 24 hours a BAC of 0.10%, above the 0.08% legal driving limit in the United States. Source: NIOSH (CDC), "NIOSH Training for Nurses on Shift Work and Long Work Hours", module 3, page 8 - More adenosine receptors (After 24 h awake, Shown in humans)
In 12 volunteers, after 24 hours without sleep, A1 adenosine receptors increased in the brain, by up to 15.3% in the orbitofrontal cortex, at the front (Elmenhorst, 2007). Source: Elmenhorst et al., "Sleep deprivation increases A1 adenosine receptor binding in the human brain: a positron emission tomography study", J Neurosci, 2007 - A slight lift in the morning (From 24 to 34 h awake, Hypothesis)
On the morning of day 2, the body clock boosts wakefulness again: you feel a little better without having slept. But sleep pressure keeps rising and takes over again in the evening. Source: Borbély, "A two process model of sleep regulation", Hum Neurobiol, 1982 - Estimated curves (Throughout, Hypothesis)
The shape of the curves follows the cited studies; heights are relative levels, not measurements.
What happens the day after an all-nighter?
All day long, you feel drowsier, hungrier and react more strongly to emotions. The early afternoon slump is deeper. Percentages measured; curves estimated.
| Hours awake or time of day the next day | Sleepiness (dotted) | Sleepiness after a good night (dotted) | Hunger (dotted) | Emotional reactions (dotted) | What happens |
|---|---|---|---|---|---|
| 7 a.m. | 70 | 30 | 55 | 55 | the next day, 24 h without sleep |
| 9 a.m. | 62 | 12 | 48 | 57 | the next day, 26 h without sleep |
| 11 a.m. | 65 | 10 | 64 | 60 | the next day, 28 h without sleep |
| 1 p.m. | 78 | 22 | 55 | 64 | the next day, 30 h without sleep |
| 3 p.m. | 83 | 26 | 54 | 68 | the next day, 32 h without sleep |
| 5 p.m. | 71 | 14 | 64 | 70 | the next day, 34 h without sleep |
| 7 p.m. | 64 | 12 | 75 | 72 | the next day, 36 h without sleep |
| 9 p.m. | 65 | 15 | 53 | 76 | the next day, 38 h without sleep |
| 11 p.m. | 90 | 45 | 50 | 80 | the next day, 40 h without sleep |
Key points
- The brain uses less energy (All day, Shown in humans)
In 17 people, after 24 hours without sleep, the brain used less glucose, especially in the thalamus, the prefrontal cortex and the parietal cortex: the areas for attention and judgment (Thomas, 2000). Source: Thomas et al., "Neural basis of alertness and cognitive performance impairments during sleepiness. I. Effects of 24 h of sleep deprivation on waking human regional brain activity", J Sleep Res, 2000 - Microsleeps (All day, Shown in humans)
The brain can switch off for 0.5 to 15 seconds without you choosing to: in 20 people, during these microsleeps, activity in the thalamus, the relay for the senses, dropped (Poudel, 2014). Source: Poudel et al., "Losing the struggle to stay awake: divergent thalamic and cortical activity during microsleeps", Hum Brain Mapp, 2014 - More ghrelin, more hunger (All day, Shown in humans)
In 9 men, after an all-nighter, ghrelin, the hunger hormone, was 22% higher (0.85 versus 0.72 ng/mL) and hunger was rated 3.9 versus 1.7 after a normal night. Leptin did not change. Source: Schmid et al., "A single night of sleep deprivation increases ghrelin levels and feelings of hunger in normal-weight healthy men", J Sleep Res, 2008 - More calories (From 11 a.m. to 9 p.m., Shown in humans)
In 12 men, a single night cut to 4 hours led them to eat 559 more calories the next day, about 22% more (Brondel, 2010). Source: Brondel et al., "Acute partial sleep deprivation increases food intake in healthy men", Am J Clin Nutr, 2010 - The afternoon slump (From 1 p.m. to 4 p.m., Shown in humans)
Early afternoon is a natural dip in alertness, even after a good night (Monk, 2005). After an all-nighter, it adds to the sleep debt. Source: Monk, "The post-lunch dip in performance", Clinics in Sports Medicine, 2005 - Emotions held back less (All day, Shown in humans)
After about 35 hours without sleep, the amygdala, the emotion center, reacted much more strongly to unpleasant images and was less connected to the prefrontal cortex (Yoo, 2007). The often-quoted difference of about 60% is to be checked. Source: Yoo et al., "The human emotional brain without sleep: a prefrontal amygdala disconnect", Curr Biol, 2007 - A debt that adds up (All day, Shown in humans)
In 48 adults, sleeping 6 hours a night for 14 days hurt attention as much as 2 all-nighters in a row (Van Dongen, 2003). Source: Van Dongen et al., "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 - Estimated curves (All day, Hypothesis)
Only the figures in the notes are measured; the curves show the trends described in the studies.
Nap, coffee, sleep: how do you recover after an all-nighter?
A coffee helps for a few hours, and so does a 10 to 20-minute nap, but only sleep clears the debt. Curves estimated from published durations.
| Hours awake or time of day the next day | Alertness with no help (dotted) | With a coffee at 8 a.m. (dotted) | With a 10-minute nap at 2 p.m. (dotted) | After a good night, for comparison (dotted) | What happens |
|---|---|---|---|---|---|
| 7 a.m. | 35 | 35 | 35 | 70 | the next day, 24 h without sleep |
| 9 a.m. | 38 | 58 | 38 | 88 | the next day, 26 h without sleep |
| 11 a.m. | 36 | 60 | 36 | 90 | the next day, 28 h without sleep |
| 1 p.m. | 25 | 35 | 25 | 78 | the next day, 30 h without sleep |
| 3 p.m. | 19 | 23 | 50 | 74 | the next day, 32 h without sleep |
| 5 p.m. | 27 | 29 | 32 | 86 | the next day, 34 h without sleep |
| 7 p.m. | 33 | 33 | 32 | 88 | the next day, 36 h without sleep |
| 9 p.m. | 33 | 33 | 33 | 85 | the next day, 38 h without sleep |
| 11 p.m. | 15 | 15 | 15 | 55 | the next day, 40 h without sleep |
Key points
- Coffee masks fatigue (From 8 a.m. to 1 p.m., Shown in humans)
Caffeine takes adenosine's place on its receptors: the fatigue signal is masked, not erased (Fredholm, 1999). From about 40 to 300 mg, it improves alertness, attention and reaction time, less so memory and reasoning (McLellan, 2016). Source: McLellan, Caldwell and Lieberman, "A review of caffeine’s effects on cognitive, physical and occupational performance", Neurosci Biobehav Rev, 2016 - It lasts a long time (From 10 a.m. to 4 p.m., Shown in humans)
Half of the caffeine leaves the blood in about 5 hours, from 1.5 to 9.5 hours depending on the person (IOM, 2001). An afternoon coffee can disturb your recovery night. Source: Institute of Medicine, "Caffeine for the Sustainment of Mental Task Performance", chapter Pharmacology of Caffeine, 2001 - A 10-minute nap (From 2 p.m. to 5 p.m., Shown in humans)
In 24 young adults who had slept little, a 10-minute nap at 3 p.m. improved alertness right away, for 155 minutes. With 20 minutes, the benefit came 35 minutes after waking; with 30 minutes, people first woke up groggy (Brooks and Lack, 2006). Source: Brooks and Lack, "A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative?", Sleep, 2006 - Coffee, then a nap (From 2 p.m. to 5 p.m., Shown in humans)
In 10 young adults, a 200 mg coffee taken just before a 20-minute nap gave the best alertness for the following hour, better than the nap alone (Hayashi, 2003). Source: Hayashi, Masuda and Hori, "The alerting effects of caffeine, bright light and face washing after a short daytime nap", Clin Neurophysiol, 2003 - Only sleep clears the debt (From 8 p.m., Shown in humans)
In 15 men kept awake for 52 hours, a 14-hour recovery night brought adenosine receptors back to their normal level (Elmenhorst, 2017). Source: Elmenhorst et al., "Recovery sleep after extended wakefulness restores elevated A1 adenosine receptor availability in the human brain", PNAS, 2017 - Sometimes more than one night (From 8 p.m., Shown in humans)
After 7 nights of 3 hours, a first 8-hour night quickly restored reaction speed; after 7 nights of 5 or 7 hours, 3 nights of 8 hours were not enough to recover fully (Belenky, 2003). Source: Belenky et al., "Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose-response study", J Sleep Res, 2003 - Estimated curves (All day, Hypothesis)
The durations of effect come from the studies; the height of the curves is an estimate.
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