Alcohol Aids Sleep Onset, Disrupts Overall Quality

Alcohol is often used as a sleep aid - with some people crediting a "nightcap" with helping them fall asleep more easily. But while it might be nice to unwind after a long day with a glass of wine or a beer, alcohol may not be as beneficial for sleep as some think. In fact, it may actually lead to a worse night's sleep overall.

If alcohol is consumed before bed, it can initially have a sedative effect - making you fall asleep more quickly . But while we may think a nightcap shortens the time it takes to fall asleep, recent research shows this sedative effect only really occurs after drinking higher doses of alcohol - between 3-6 standard glasses of wine , depending on the person - within three hours of bed.

And while this might seem beneficial, using alcohol to fall asleep is not recommended. This is not only because of the negative health effects of drinking alcohol , but also because alcohol disrupts sleep later in the night.

This disruption mainly affects REM (rapid eye movement) sleep . Alcohol delays the first episode of REM sleep - and reduces the subsequent amount of REM sleep you get throughout the night. It can also make you wake up more often or lead to lighter sleep in the latter part of the night. This is significant, as REM sleep - sometimes called "dreaming sleep" - is thought to be important for memory and regulating emotions.

These disruptions to REM sleep are even seen after drinking low doses of alcohol (around two standard drinks) within three hours of bedtime .

Sleep disruptions of any kind can make you feel more tired the following day. Disturbed REM sleep can also lead to impairments in the consolidation of memories, cognitive function and how you regulate your emotions.

It's worth noting that most research only focuses on the effect of alcohol on a single night of sleep. Generally, less is known about the effect that multiple nights of drinking has on sleep - with only a small number of studies (which had low numbers of participants) showing inconsistent results.

However, one study did indicate that after multiple nights of drinking, disruptions to sleep were still apparent during the first night without drinking. This suggests it may take time for sleep to recover after repeated nights of drinking.

Why alcohol affects sleep

While there's still more research to be done to understand exactly why alcohol affects different components of sleep - particularly in those who drink large amounts on a regular basis - we do know of a few mechanisms linking alcohol consumption to sleep.

First, alcohol increases the action of a chemical messenger in the brain called GABA. This has a sedative effect, thought to contribute to the sleepy feeling many people experience when drinking alcohol. Alcohol may also increase levels of adenosine , a chemical messenger that is important for sleepiness.

But the increase in these chemicals when drinking is short-lived. Once the body has metabolised the alcohol, there's often a "rebound effect" in which the body tries to compensate for the alcohol-induced changes in physiological functions and sleep. This causes the light and disrupted sleep that people experience during the latter part of the night after drinking.

Alcohol also affects circadian rhythms - the 24-hour body clock that responds to environmental light cues in order to synchronise our sleep-wake cycle. One of the ways our circadian rhythm does this is through the release of specific hormones at certain times of the day. For instance, our body will release melatonin during the hours of darkness to help us feel tired - and stay asleep throughout the night.

But alcohol affects the production of melatonin and alters our body temperature . The timing and amount of melatonin that's released and a decrease in core body temperature are important for sleep. Changes in these will result in changes in sleep.

Further, alcohol relaxes the muscles in the airways, which can exacerbate snoring - potentially disrupting the sleep of your partner too.

Finally, due to its diuretic effect , drinking alcohol before bed may mean more bathroom visits during the night - further disrupting sleep.

How to get a better night's sleep

If you sometimes use alcohol to help you fall asleep, here are some things you can do instead to get a better night's sleep:

• Keep a regular schedule. Going to bed and waking at the same time each day helps regulate the body's circadian rhythms and improve sleep .
• Create a peaceful sleep environment. A cool, quiet and dark room is ideal for getting a good night's sleep.
• Create a consistent bedtime routine. Do some relaxing activities before bed to help the brain wind down - such as reading or taking a bath.
• Limit your afternoon caffeine intake. Caffeine is a stimulant - and its effects can last many hours, with half of it remaining in our bodies four-to-six hours after consuming it, on average. Only consume caffeinated foods and drinks earlier in the day.
• Get active. Physical activity can be beneficial for regulating circadian rhythms and helping us feel tired at the end of the day. Even better if you can do your workout in the natural morning light, as morning light exposure regulates circadian rhythm and improves sleep quality .

The good news for people who enjoy a nightcap or the odd night out is that many of the negative effects of alcohol on sleep are relatively short-lived, and can be reversed by avoiding alcohol or reducing intake. While it may take longer for sleep and circadian rhythms to return to normal in people who drink more often in higher amounts, quitting alcohol can help.

Better sleep will not only leave you feeling more refreshed, it will also benefit your overall health and wellbeing .

Emma Sweeney has previously received funding from the Society for Endocrinology.

Fran Pilkington-Cheney does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.