Alcohol

Alcohol can help you fall asleep, then breaks up the second half of the night, cuts REM sleep, raises your heart rate and lowers HRV. Less, and earlier, is better.

• Evidence: Strong
• Medium effort
• Free
• Works: tonight

Why it matters

A 2013 review of all known studies in healthy volunteers found that, at all doses, alcohol shortened the time to fall asleep and made the first half of the night more solid. The second half was more disrupted. The most consistent effect on REM (dreaming) sleep was that the first REM period came later, and most studies at moderate and high doses found less REM over the whole night [2].

A 2025 meta-analysis of 27 studies is more cautious about the upside. Faster sleep onset and faster entry into deep sleep only showed up at high doses, about five standard drinks or more. REM loss started at low doses, about two drinks, and grew with each extra drink. The effects on total sleep, efficiency and wake-ups were too uncertain to call [1].

Alcohol also changes your heart overnight. In 4,098 Finnish employees who wore heart monitors in daily life, nights after drinking had a higher heart rate and lower HRV in the first 3 hours of sleep, compared with the same person’s nights without alcohol. Heart rate was up by an average of 1.4 beats per minute after a low dose, 4.0 after a moderate dose and 8.7 after a high dose. RMSSD, the HRV measure many wearables use, fell by 2.0, 5.7 and 12.9 ms. Even low intake had a measurable effect, and being young or physically active didn’t protect people [4]. A small lab trial in 10 young men found the same dose-dependent pattern [5].

How to do it

1. Know what a drink is. In the US, a standard drink is about 14 g of pure alcohol: 12 fl oz (355 mL) of 5% beer, 5 fl oz (148 mL) of 12% wine, or 1.5 fl oz (44 mL) of 40% spirits [7].
2. Keep it to one or two on nights you care about sleep. Two drinks is around the dose where REM loss starts showing up [1]. Less is better.
3. Stop early. In 10 men in their 60s, a moderate dose (0.55 g per kg of body weight) 6 hours before bed still cut sleep time, efficiency and REM, and doubled time awake in the second half of the night. Their breath alcohol was already zero at bedtime [3]. No study we found sets a safe cutoff, so earlier is better and “with dinner” beats “nightcap”.
4. Don’t use it as a sleep aid. The sedation is short and the second half of the night pays for it [2].
5. Keep your wake time. Sleeping in after a big night shifts your clock; see consistent wake time.

If you snore or might have sleep apnea, be extra careful: a meta-analysis of 14 trials found alcohol increased breathing pauses during sleep, more so in snorers and people with sleep apnea [6]. See when to see a doctor.

Common mistakes

• “It helps me sleep.” It may help you drop off, but REM and the second half of the night get worse [1][2].
• Thinking a glass or two doesn’t count. Heart rate and HRV changed even at low intake [4], and REM loss begins around two drinks [1].
• Trusting that you’ve “sobered up”. Sleep was still disrupted after breath alcohol was back to zero [3].
• Pairing it with sleeping pills or other sedatives. Don’t. Ask your doctor or pharmacist about any medication you take.

Effect on your sleep score

• Resting heart rate: up, by about 1 to 9 beats per minute depending on dose, early in the night [4]. Oura lists alcohol among things that can raise your resting heart rate, and suggests avoiding it if your heart rate reaches its lowest point late in the night [8].
• HRV: down, in a dose-dependent way [4][5]. This is often the clearest sign of a drink in your data.
• REM: less, and later [1][2].
• Time to fall asleep and deep sleep: may be shorter or more at high doses only [1].
• Efficiency and wake-ups: more waking in the second half of the night in lab studies [2][3], though the meta-analysis couldn’t pin down the size [1].

How confident: high for REM, heart rate and HRV; low for total sleep and efficiency.

Evidence

Rated Strong. A meta-analysis of 27 studies [1] and a review of all earlier studies [2] agree that alcohol reduces REM in a dose-dependent way. The heart rate and HRV findings come from a very large real-world study [4] and a small controlled trial [5].

Limits: lab studies mostly gave a single dose to young, healthy volunteers, often men. The heart rate study relied on people reporting their own drinking, and only covered the first 3 hours of sleep [4]. The timing study had 10 older men [3]. The meta-analysis authors note that sex differences and individual metabolism still need study [1].

General information for healthy adults, not medical advice. If you have a sleep problem that lasts, read when to see a doctor. Sources checked 4 October 2026. Spot a mistake? Tell us.