The Science Behind How Alcohol Affects the Quality of Your Sleep
Whilst, historically, alcohol has been used as a way of getting to sleep, modern science now knows of its negative effects on the sleep cycle. Although alcohol can make you drowsy, in the long run, it can actually cause poor sleep hygiene.
The way your body works whilst you are asleep is finely calibrated to meet your physical and emotional needs — and drinking too much alcohol disrupts this natural circadian rhythm by preventing you from getting enough quality, restorative rest. Here’s what happens to your sleep quality consuming too much alcohol.
How does alcohol affect sleep quality?
Alcohol affects REM sleep
Your sleep is regulated by cycles of activity in the brain, comprising of two primary states: non-rapid eye movement (NREM) and rapid eye movement (REM). You begin the sleep cycle with NREM sleep followed by a short burst of REM sleep. Thereafter, you proceed to get more NREM and REM sleep in each 90-minute sleep cycle throughout the night. Learn more about REM, light and deep sleep here.
While all stages of the sleep cycle are vitally important to your overall wellbeing, REM sleep — which is the point at which you dream — is critical for emotional wellbeing. During this stage of rest, processes affecting mood regulation, mental restoration, cognition, and memory happen throughout the body, allowing us to restore our mental and emotional wellbeing every day.
A review of 27 studies demonstrates the negative effects that alcohol can have on REM sleep.i According to these findings, even though alcohol helped participants fall asleep faster and rest more deeply for a short period, it reduced overall REM (rapid eye movement). Not getting enough quality REM sleep can have various negative effects on cognitive and emotional health.
Alcohol causes fragmented sleep
Drinking in the evening leads to decreased sleep onset latency, too, which can result in disturbed and fragmented rest.ii In the first half of the night — as your body is metabolising alcohol — you will fall asleep quicker and spend more time in deep sleep (also known as stage three of NREM sleep).
However, this is offset by increased sleep disturbances in the second half of the night. Once the alcohol is fully metabolised and any of its sedative properties dissipate, your body will experience a ‘rebound effect’.iii At this point, you will transition from deeper to lighter sleep, with frequent awakenings and arousals. Although you may not remember waking up throughout the night, you will wake up in the morning feeling tired and unfocused.
Interference with your sleep-wake cycle
Drinking alcohol in the evening also has a significant impact on your sleep hormone, melatonin. This sleep-regulating hormone is essential in helping you to fall asleep. There’s a body of evidence suggesting that drinking moderately up to an hour before bed can suppress melatonin production by nearly 20 per cent.iv
Furthermore, alcohol increases levels of adenosine — a chemical that naturally regulates sleep. The longer you are awake, the more your levels of adenosine rise, which inhibits other chemicals that promote wakefulness. Alcohol’s adenosine-enhancing effects can lead to you sleep more than you would usually, disrupting your biological sleep cycle.v
Alcohol affects bodily functions
While you are asleep, various biological processes, including those involved in your bladder, are put into a sort of hibernation mode. But since alcohol is a diuretic — a drug that increases the passing of urine — it disrupts this practical system by making you need to use the bathroom more.vi This further interrupts your natural sleeping pattern and compromises rest.
How much alcohol does it take to affect sleep?
While heavy drinking can exacerbate the effects of alcohol on sleep, even regular, moderate drinking is enough to create sleep problems. Just one glass of alcohol in the evening can affect the quality of your sleep. Generally speaking, if you’re going to bed feeling slightly inebriated, you’ve probably had too much to drink and your sleep will be impaired.
As a rule of thumb, aim to drink moderately — that is, no more than two drinks — a maximum of two to three times per week. You should always drink two glasses of water for every alcoholic beverage to flush out the alcohol and promote better sleep quality.
When’s the best time to drink alcohol?
If you want to enjoy a drink whilst minimising the negative effects of alcohol, the best time of day for your body to metabolise alcohol is early to mid-evening. This is because it takes around an hour for each serving of alcohol to be processed by the body.
How can I reduce my alcohol consumption?
Reducing your alcohol consumption is a sensible place to start if you want to prioritise your sleep quality and wake up energised.
Here are some of our tips to help moderate your intake:
Mix a glass of wine with mineral water
Mix beer or stout with lemonade
Avoid situations where there’s pressure to drink in rounds
Alternate an alcohol-free beverage with an alcoholic one
Use smaller glasses for your drinks
Don’t be afraid of saying ‘no, thank you’
Have drink-free days of the week
Most of us like to unwind with a drink now and again, but if you think alcohol is regularly affecting your quality of sleep, it could mean that you need to cut back. Restful sleep is one of the most important aspects of staying healthy. Without enough of it, the accumulated poor sleep hygiene can compromise your overall wellbeing.
Want to learn more about how sleep affects our bodies? Feel free to explore the rest of our sleep hub.
Ebrahim. I., Shapiro. C., Williams. A. & Fenwick. P. (2013). Alcohol and Sleep I: Effects on Normal Sleep. Alcoholism: Clinical and Experimental Research. 37(4), 539`-549.
Stein. M.D. & Friedmann. P.D. (2005). Disturbed sleep and its relationship to alcohol use. Substance abuse. 26(1), 1–13.
Colrain. I.M., Nicholas. C.L. & Baker. F.C. (2014). Alcohol and the sleeping brain. Handbook of clinical neurology. 125, 415–431.
Rupp. T., Acebo. C. & Carskadon. M. (2007). Evening Alcohol Suppresses Salivary Melatonin in Young Adults. Chronobiology International. 24(3), 463-470.
Wiers. C. (2014). Adenosine Sheds Light on the Relationship between Alcohol and Sleep. Journal of Neuroscience. 34(23), 7733-7734.
Thakkar. M., Sharma. R. & Sahota. P. (2015). Alcohol disrupts sleep homeostasis. Alcohol. 49(4), 299-310.
Olivia Salter has always been an avid health nut. After graduating from the University of Bristol, she began working for a nutritional consultancy where she discovered her passion for all things wellness-related. There, she executed much of the company’s content marketing strategy and found her niche in health writing, publishing articles in Women’s Health, Mind Body Green, Thrive and Psychologies.