Why does drinking alcohol affect your sleep?

How alcohol affects your sleep

Disrupted sleep

At first, drinking alcohol can make you feel sleepy and relaxed, because it has a sedative effect on your central nervous system. Although this means you might fall asleep quicker, drinking too much alcohol has been linked to poor sleep quality, which means you're more likely to have a bad night's sleep.

After you drink alcohol, it is absorbed into your bloodstream and processed in the liver. How long this takes can depend on many factors - including the amount of alcohol, your age, how much you've eaten, your sex, and your body type.

If you fall asleep after drinking too much, your body will continue to break down the alcohol during the night. As your body works to lower your blood alcohol level, you may experience disrupted sleep and wake up more often than usual.

In turn, this affects all the different phases of sleep we get a night - which are usually finely tuned to make sure we are rested and our brains can function properly. This includes disrupting our restful deep sleep, or REM sleep, leading to more periods of wakefulness.

The occasional bad night's sleep may be unpleasant, but is unlikely to have a lasting effect. However, studies have shown that a continuous lack of REM sleep can negatively affect memory and learning¹, may impact our emotional abilities² and increase the risk of migraine³. Poor sleep has also been linked to an increased risk of mental health problems such as anxiety and depression, hypertension, obesity, heart attack and stroke⁴.

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Alcohol and toilet trips

If you drink alcohol before bed, you may also find yourself getting up more often in the night to go to the toilet. Alcohol is a diuretic, which means you pee and sweat more⁵. This can also make you feel even more dehydrated.

Alcohol and sleep apnoea

Research has also shown that alcohol use can worsen the symptoms of sleep apnoea, a disorder in which your breathing stops and starts while you sleep⁶. The most common type is called obstructive sleep apnoea. Even if you don't have the condition, studies show that moderate or heavy drinking can cause episodes of obstructive sleep apnoea.

Why drinking makes you snore

Drinking alcohol relaxes the muscles around your throat, making you more likely to snore too. This is because alcohol can make the tissue in the nose swell, which can cause congestion and create a need to breathe through the mouth, making you snore. Snoring may well disturb your own sleep by waking you up - but it is likely to cause problems for partners too.

Alcohol guidelines

Men and women are advised not to drink more than 14 units of alcohol a week. It helps to know how many units are in a drink - 14 units is the same as six pints of average-strength beer or ten small glasses of lower-strength wine.

If you want to cut down, it can help to have several drink-free days each week. If you're at a party, you could try opting for a soft drink or glass of water between alcoholic drinks, which will help keep you hydrated and mean you drink less alcohol over the night.

Further reading

1. Schmid et al: Sleep-dependent motor memory consolidation in healthy adults: A meta-analysis.

2. Krause et al: The sleep-deprived human brain.

3. Burtisch et al: Nightly sleep duration, fragmentation, and quality and daily risk of migraine.

4. Institute of Medicine (US) Committee on Sleep Medicine and Research: Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem.

5. Roberts: Mechanism of dehydration following alcohol ingestion.

6. Simou at al: Alcohol and the risk of sleep apnoea - a systematic review and meta-analysis.