The short answer
Alcohol works in two halves. A review of every known sleep study in healthy volunteers found that at all doses it helps you fall asleep faster and makes the first half of the night deeper, then increases disruption in the second half, which is when many people wake around 3 a.m. Lab and real-world studies also found that evening drinks keep your heart rate higher and your body less recovered during sleep, even at low doses.
Key takeaways
- At every dose studied, alcohol shortened the time to fall asleep and then increased sleep disruption in the second half of the night.
- Alcohol delayed the first period of REM (dreaming) sleep at all doses and cut total REM sleep at moderate and high doses.
- Evening drinks raised heart rate and lowered heart rate variability during sleep in a lab study, with bigger effects after more drinks.
- In 4,098 Finnish employees, even low alcohol intake was linked with poorer physical recovery in the first hours of sleep.
- Alcohol is not a good sleep aid: the deeper first half comes at the cost of a more broken second half.
Alcohol and sleep work in two halves of the night
In 2013, sleep researchers in London reviewed every known study on how alcohol affects sleep in healthy volunteers. Their summary was consistent across doses: alcohol reduces the time it takes to fall asleep, makes the first half of the night more consolidated, and increases sleep disruption in the second half.
That pattern explains a very common experience. You fall asleep quickly after a few drinks, sleep heavily for a few hours, then find yourself awake in the early hours, often around 3 or 4 a.m., unable to settle. The exact time depends on when you went to bed and how much you drank, but the shape of the night, deep first and broken later, is what the studies describe.
What happens to REM and deep sleep after a drink
Sleep moves through stages, including deep slow-wave sleep and REM sleep, the stage most linked with dreaming. The review found that alcohol increased slow-wave sleep in the first half of the night in most studies, across doses, ages and both sexes.
REM sleep was affected differently. The onset of the first REM period was significantly delayed at all doses, and the authors called this the most recognisable effect of alcohol on REM sleep. Across the whole night, the percentage of REM sleep fell in most studies at moderate and high doses, with no clear trend at low doses.
| Part of sleep | Effect of alcohol | At which doses |
|---|---|---|
| Time to fall asleep | Shorter | All doses |
| First half of the night | More consolidated, more deep (slow-wave) sleep | All doses (slow-wave increase in most studies) |
| Second half of the night | More sleep disruption | All doses |
| First REM (dream) sleep | Starts significantly later | All doses |
| Total REM sleep | Lower | Moderate and high doses; no clear trend at low doses |
Your heart works harder on nights you drink
Waking up is not the only change. In a 2021 laboratory study published in the journal Sleep, 26 healthy adults aged 30 to 60 slept in the lab on three nights: after no alcohol, after a low dose (1 standard drink for women, 2 for men) and after a high dose (3 for women, 4 for men). Drinking before bed raised heart rate across the night, reduced heart rate variability, weakened the reflex that steadies blood pressure and increased the activity of the body's "fight or flight" system. The effects were strongest after the higher dose.
A much larger real-world study came to a similar conclusion. Researchers in Finland analysed heart-rate recordings from 4,098 employees on nights with and without alcohol. Alcohol was linked, in a dose-dependent way, with less recovery during the first three hours of sleep, and the effect showed up even at low intake. On average, the measure of physical recovery fell by 9.3 percentage units after low intake, 24.0 after moderate intake and 39.2 after high intake.
A racing heart and a body that is not recovering do not make for restful sleep, which may be part of why a night after drinking can feel unrefreshing even when you slept for hours.
Is alcohol a good sleep aid?
Because alcohol helps people fall asleep faster, some use a drink as a nightcap. The research suggests that trade is a poor one: the quicker, deeper start comes with a more disrupted second half of the night, a delayed first REM period and, at moderate and higher doses, less REM sleep overall. Add a higher heart rate and poorer overnight recovery, and alcohol looks more like a sleep disruptor than a sleep aid.
If you regularly rely on a drink to get to sleep, that is worth taking seriously. Our sister site GoodSleep has free tools for sleep problems that do not involve alcohol.
Sleep in the first weeks after you stop drinking
Many people expect to sleep better as soon as they stop drinking, and some do. Others find their sleep is unsettled at first. Difficulty sleeping is one of the alcohol withdrawal symptoms the NHS lists, and withdrawal symptoms usually begin within 6 to 12 hours of the last drink and last 3 to 7 days.
In people who were being treated for alcohol dependence, a 2003 review found that insomnia was common, affecting 36% to 72%, and could last for weeks to months after they stopped drinking. That finding comes from people with long-term heavy drinking, not from people taking a month off, so it should not worry most Dry January participants. If poor sleep lasts, or you have other withdrawal symptoms such as shaking, sweating or a racing heart, talk to a doctor.
What helps if you drink and want to sleep better
The studies above point to a few practical steps. The lab study found bigger effects at higher doses, so fewer drinks on an evening means less disruption. The second-half disruption follows alcohol in your system, so keeping alcohol further from bedtime is a reasonable choice, although the studies we cite did not test a specific cut-off time.
The most reliable way to avoid alcohol-related sleep disruption is to have alcohol-free evenings. If you want to try a run of them, our Dry January tracker works for any month and counts every alcohol-free night.
- Have fewer drinks on nights you drink: effects grew with dose in the lab study.
- Keep some nights completely alcohol-free and notice how you sleep on them.
- Do not use alcohol as a sleep aid; the deeper start costs you a more broken second half.
- If you wake with a racing heart, sweating or shaking when you have not had a drink, see a doctor.
Common questions
Why do I wake up so early after drinking?
A review of sleep studies found that alcohol increases sleep disruption in the second half of the night at all doses, after making the first half deeper. Waking early, often in the small hours, is how many people notice that second-half disruption.
Does even one drink affect sleep?
In the Finnish study of 4,098 employees, even low alcohol intake was linked with poorer physical recovery in the first hours of sleep. The sleep review found the first-half and second-half pattern at all doses, although effects on REM sleep were less clear at low doses.
Why is my heart racing in bed after drinking?
In a 2021 lab study, drinking before bed raised heart rate during the night and increased "fight or flight" activity, more so after higher doses. If your heart races when you have not been drinking, or you have chest pain or feel faint, get medical help.
How long until sleep improves after I stop drinking?
There is no single answer. For most people the alcohol-related disruption stops with alcohol-free nights, but withdrawal can disturb sleep for several days, and in people treated for alcohol dependence insomnia sometimes lasted weeks to months. Persistent poor sleep is worth discussing with a doctor.
When to get help
This site offers self-help tools and information, not medical advice. Talk to a doctor, or call one of the lines below, if:
- you feel shaky, sweaty, sick or anxious when you haven't had a drink;
- you find it hard to stop once you start, or you want to cut down and can't;
- drinking is causing problems with your health, work or the people close to you.
Before you stop: It can be very dangerous to stop drinking suddenly if you are dependent on alcohol. If you get withdrawal symptoms, get medical help before you try to stop drinking.
Free, confidential helplines
- United States:SAMHSA National Helpline1-800-662-HELP (4357)Treatment referral and information, 24/7.
- United States:988 Suicide & Crisis LifelineCall or text 988Free and confidential support for people in distress, 24/7.
- United Kingdom:Drinkline0300 123 1110The national alcohol helpline, free and in complete confidence. Weekdays 9am to 8pm, weekends 11am to 4pm.
In an emergency, call your local emergency number.
Sources
- Ebrahim IO, Shapiro CM, Williams AJ, Fenwick PB. (2013). Alcohol and sleep I: effects on normal sleep. Alcoholism: Clinical and Experimental Research, 37(4), 539–549. PMID 23347102
- de Zambotti M, Forouzanfar M, Javitz H, et al. (2021). Impact of evening alcohol consumption on nocturnal autonomic and cardiovascular function in adult men and women: a dose-response laboratory investigation. Sleep, 44(1), zsaa135. PMID 32663278
- Pietilä J, Helander E, Korhonen I, Myllymäki T, Kujala UM, Lindholm H. (2018). Acute Effect of Alcohol Intake on Cardiovascular Autonomic Regulation During the First Hours of Sleep in a Large Real-World Sample of Finnish Employees: Observational Study. JMIR Mental Health, 5(1), e23. PMID 29549064
- Brower KJ. (2003). Insomnia, alcoholism and relapse. Sleep Medicine Reviews, 7(6), 523–539. PMID 15018094
- Alcohol-use disorder. NHS. nhs.uk
Keep your progress on your phone
We're building a companion mobile app for dry months and drink-free days, with reminders you choose. It isn't out yet. Leave your email to get notified when it launches.