How Does Alcohol Affect Your Sleep?

Alcohol makes it easier to fall asleep, and that’s where its benefits for sleep end. As your body breaks it down during the night, the second half of your sleep becomes lighter and more broken, REM sleep is delayed and often reduced, and your heart works harder than on a sober night. The effects grow with the amount, but even small amounts show up in heart rate during sleep.

This article is general information, not medical advice.

What Happens Over the Night

Ebrahim and colleagues reviewed every known study of alcohol and sleep in healthy volunteers. At all doses:

• Falling asleep is quicker, and the first half of the night is more consolidated, with more deep sleep.
• The second half is more disrupted, with more waking, as the alcohol is metabolised.
• The first REM period is delayed, the most consistent effect on REM, and total REM over the night is reduced at moderate and high doses.

Your Heart Notices, Even at Small Doses

In a study of 4,098 Finnish employees wearing heart rate monitors, Pietilä and colleagues found that alcohol raised heart rate and lowered heart rate variability during the first three hours of sleep in proportion to the dose. The recovery state they derived from heart rate variability fell by about 9, 24, and 39 percentage points after low, moderate, and high intake, and the effects were similar in women and men and in active and sedentary people. That’s why a drink or two often shows on a watch the next morning as a higher resting heart rate and lower HRV.

What Helps

• Drink earlier. Alcohol finished well before bed has more time to clear before you sleep.
• Drink less on nights that matter. The effects are dose-related.
• Don’t use it as a sleep aid. The quicker start comes with a worse second half of the night.

Following It in Kaizora

Dietary Alcohol comes from what you drink, logged on Food Log or imported from Cronometer, and is shown in grams or your country’s standard drinks; see What Is a Standard Drink? Each night’s sleep counts on the morning you wake, so put alcohol beside Resting Heart Rate, Heart Rate Variability (RMSSD), or REM Sleep Time on Correlations by day, and the next-morning effect shows; see Comparing Metrics. Discover (Plus) also looks for links with a lag of a few days. The Timeline puts last night’s drinks beside the night itself.

The Short Version

• Alcohol speeds sleep onset but disrupts the second half of the night.
• It delays REM sleep and, at moderate and high doses, reduces it.
• Even small amounts raise heart rate and lower HRV in the first hours of sleep.

Sources

• Ebrahim IO et al., “Alcohol and sleep I: effects on normal sleep,” Alcoholism: Clinical and Experimental Research 37, no. 4 (2013). doi:10.1111/acer.12006
• Pietilä J et al., “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, no. 1 (2018): e23. doi:10.2196/mental.9519