Alcohol has played a vital role in human culture for thousands of years. As well as the ability to intoxicate, its sleep-inducing effects are legendary. is So it should come as no surprise that booze - cheap, readily available and prescription-free - is one of the most common sleep aids on the planet. Whilst it undeniably has soporific qualities, acohol's actual effect is biphasic, ie in two phases.
To begin, the booze acts as a stimulant, flooding the brain with endorphins, feel-good chemicals which make us more talkative, self-confident and less socially inhibited. But after a while, the buzz wears off and the alcohol starts to act as a sedative, causing you to feel drowsy. At higher blood alcohol levels, this can become dangerous, leading to loss of consciousness or worse.
This has understandably led to a widespread belief that a drink or two may be a perfectly good way to help you fall asleep. Hence, the tradition of a night-cap before bed, or grandma dipping the baby's pacifier into a glass of whiskey. But in the last few decades, as modern science has probed deeper into the mysteries of our sleeping lives, the evidence is beginning to stack up - drinking alcohol has complex and profound effects on sleep, most of which are detrimental to our health.
The science of sleep and alcohol
A 2013 review of 27 published studies found some broad themes across the research; alcohol reduces the time it takes to fall asleep and increases the amount of deep sleep during the first half of the night. However, this is offset by increased sleep disturbances in the second half of the night. Dr Irshaad O. Ebrahim one of the researchers said,
"This review confirms that the immediate and short-term impact of alcohol is to reduce the time it takes to fall asleep. In addition, the higher the dose, the greater the impact on increasing deep sleep. This effect on the first half of sleep may be partly the reason some people with insomnia use alcohol as a sleep aid. However, the effect of consolidating sleep in the first half of the night is offset by having more disrupted sleep in the second half of the night." Source
The researchers concluded that short-term alcohol use, whilst giving the impression that it improves sleep, should not be used to treat insomnia. Commenting on the findings, Chris Idzikowski, Director of the Edinburgh Sleep Centre added: "alcohol on the whole is not useful for improving a whole night's sleep. Sleep may be deeper to start with, but then becomes disrupted. Additionally, that deeper sleep will probably promote snoring and poorer breathing. So, one shouldn't expect better sleep with alcohol." Source
Is alcohol always bad for sleep?
Although high levels of blood alcohol content (BAC) certainly have a detrimental effect on sleep architecture, there is some evidence that small dosages could actually increase total sleep time. These benefits however may be outweighed by the body's rapid tolerance to alcohol's sedative properties, plus the risk of dependency. A comprehensive report commisioned by the National Institute on Alcohol Abuse and Alcoholism summarized that;
"Data from healthy people suggest, however, that tolerance to alcohol’s sedative effects probably develops rapidly. This tolerance development may lead to excessive hypnotic use and, possibly, excessive daytime use for insomniacs." Source
Alcohol and sleep architecture
Sleep architecture is a fancy name for the order and duration of the various sleep stages. Sleep falls into two basic categories; rapid eye movement, REM and non-rapid eye movement, NREM. A healthy adult typically starts their night's sleep in NREM (which is broken into 4 stages), followed by a period of REM. This cycle repeats 4 or 5 times during the night. The REM period is short , but subsequent REM stages get longer as the night progresses.
When alcohol enters the equation however, this finely choreographed behaviour is thrown into disarray. The three main ways alcohol affects sleep architecture are:
- you fall asleep faster - the technical term for the time it takes to fall asleep is sleep onset latency (SOL). The 2013 review found that "SOL is reduced at all dosages in all studies and appears to be the single most robust effect of alcohol on nocturnal sleep ".
- an increase in deep sleep - deep sleep occurs in stages 3 and 41 of NREM. Also known as slow-wave sleep (SWS). During SWS, the body heals and regenerates itself, releasing human growth hormone, and strengthening the immune system. A majority of studies have shown that drinking increases SWS during the first half of the night at all dosages.2
- a decrease in REM sleep - whilst the effect is not significant at low doses, moderate and high amounts of alcohol cause an overall reduction in total REM percentage throughout the night. In addition, it has been shown that alcohol delays the first period of REM.
To the uninitiated this might not seem such a bad thing; less time to fall asleep, a deeper slumber, and less chance of any disturbing dreams. However, just as there can be side effects with sleeping pills, alcohol can affect your sleep in numerous ways too. So here's our list of the top 8 ways that drinking alcohol can mess with your sleep.
1) The rebound effect: wide awake at 4am
A night on the booze will most likely cause you to sleep deeper during the first part of the night, but later on the chances are you will be more restless than usual. This is known as the rebound effect, and is the reason why drinkers often find themselves wide awake in the early hours of the morning.
Alcholol is a fast acting drug entering the bloodstream quickly and reaching the brain within minutes. But the effects are short lived. The liver quickly metabolises the alcohol and any sleepiness you felt quickly wears off. Once your BAC goes down, sleep variables are reversed, manifesting itself as disturbed sleep.
2) It's dangerous if you take sleeping pills
Combining prescription drugs with drinking is asking for trouble. But when your pills happen to be sleep medications, the effects can be greater than the sum of it's parts. Alcohol and sleeping pills can lead to an increased risk of accidents, overdoses and even worse. Get it wrong and this deadly cocktail can end up killing you. According to the Santa Clara University Wellness Center,
When combined with alcohol these drugs have a synergistic effect, meaning that the combined depression of the CNS is greater than the sum of the depression caused by alcohol and that of the barbiturate. This effect can be expressed with the equation 1+1 = 3 (the combined effect is greater than the effects combined).
3) Sweating like a pig
Alcohol is a chemical substance that can cause vasodilation, ie the widening of your blood vessels. When blood vessels close to the skin enlarge, the skin becomes warm. In order to maintain an optimum body temperature, your sweat glands kick into action, letting heat escape in the form of perspiration. Whilst this ultimately achieves the aim of cooling you down, it also increases the chances of sleep disturbances. Night sweats3 are common in people with alcohol dependency issues, but can also occur after bouts of heavy or binge drinking.
4) You're more likely to snore... or worse
Alcohol has many effects, including acting as a muscle relaxant. Sleep apnea, a sleep-related breathing disorder affects millions of people round the world, and is caused by the throat and airway muscles collapsing at night during sleep. If you already suffer from sleep apnea, alcohol (by means of relaxing your breathing muscles) increases the chances of making your symptoms worse45.
But it's not just people with existing sleep disorders that are affected. Alcohol can induce sleep apnea symptoms, such as snoring or interrupted breathing in perfectly healthy individuals6. Professor Karl Doghramji, director of the Sleep Disorders Center at Jefferson Hospital mentions that:
"Alcohol increases the severity of the syndrome [OSA], and may cause snoring and induce apneas in individuals without a history of obstructive sleep apnea syndrome." Source
5) It makes you pee - a lot
According to the porter in Shakespeare's Macbeth, the three things that drink provokes are "nose-painting, sleep, and urine." So why does boozing make you pee so much? It's not just the result of liquid passing through the body. Alcohol is a potent diuretic ie it makes you urinate more than you would when drinking the equivalent volume of non-alcoholic drinks. According to one study, for every 1g of alcohol drunk, urine excretion increases by 10ml.
The reason this happens is because alcohol suppresses a hormone known as vassopressin or ADH (anti-diuretic hormone)which regulates the amount of water absorbed by the kidneys. When ADH is low, instead of storing water, the kidneys dump it into the bladder, causing the urge to pee.
As if this wasn't enough, alcohol can also increase the acidic content of your urine, irritating the lining of your bladder. This can make your bladder feel fuller than it really is, creating a very strong urge to make repeated trips to the bathroom - making for some potentially very sleepless nights.
6) It's worse if you're female
A 2011 study into the effect of intoxication on healthy young adults7 found that alcohol disrupts sleep in women more than in men. These gender differences could be down tho the fact that women metabolize alcohol more quickly than men, meaning that the sedative properties of a late night drink wear off more easily, causing women to feel the second, more fragmented part of their sleep more quickly. The study found that "women objectively had fewer hours of sleep, woke more frequently and for more minutes during the night, and had more disrupted sleep than men."
7) Say goodnight to your dreams
Whilst we still don't understand fully the mechanisms of how and why we dream, recent research shows that our dreams may play a crucial role in maintaining the normal function of human physiology and brain function. One theory is that because during REM, certain neurotransmitters like serotonin are effectively switched off, we use this period of our sleep to replenish or reset these vital brain chemicals. Whilst low and moderate doses of alcohol seem to have little effect on REM sleep, high doses of alcohol have a significant impact on the amount and duration of REM. A 2013 review of sleep and alcohol found that across all of the studies, total night REM sleep percent is decreased in the at moderate and high doses. Acccording to study author, Dr Ebrahim, amongst other effects," lack of REM sleep can have a detrimental effect on concentration, motor skills".
8) It increases your chances of sleep-walking
Sleepwalking, or somnambulism is a type of parasomnia, one of many types of abnormal sleep behaviour. It most commonly occurs during NREM, in the first part of the night. Although sleepwalkers show a genetic predisposition towards the condition, according to the National Sleep Foundation, factors that increase the chances of sleepwalking include fatigue, sedative medications and alcohol. High levels of alcohol in the blood dramatically increase the amount of slow-wave sleep (SWS) you get at night, which is consistent with sleepwalking episodes, which often include quite complex, often bizarre behaviours. In 2012, office worker Becky Mason was cleared of a drink-driving conviction when a court decided that her night-time excursion was a result of a sleepwalking episode, which she'd suffered form for many years. After drinking a bottle of wine, she fell asleep, then, still in her pyjamas, got in her car and drove to work - even though it was Saturday night. Police found her car after it crashed into a lamp-post. Neuropsychiatrist Jonathon Bird who went to court to support her case said, "‘Her experience is at the extreme end of parasomnia, but the evidence strongly showed that she had indeed been asleep right up until the crash’.
So, it seems there are lots of ways that alcohol can seriously mess with your sleep. Whilst a small occasional drink before bedtime will probably do little harm, drinking moderate to high amounts of alcohol before you sleep can have lots of detrimental effects.
- As of 2008, the American Academy of Sleep Medicine (AASM) has discontinued the use of stage 4, such that the previous stages 3 and 4 now are combined as stage 3.
- Alcoholism: Clinical & Experimental Research. "Reviewing alcohol's effects on normal sleep." ScienceDaily, 22 Jan. 2013. Web. 9 Nov. 2013.
- Viera, Anthony J. et al "Diagnosing Night Sweats." American Family Physician, March 1, 2003, 1019-024.
- Alcohol, snoring and sleep apnea. J Neurol Neurosurg Psychiatry (1982) PMID: 7077345
- Effect of moderate alcohol upon obstructive sleep apnoea. Eur Respir J (2000) PMID: 11153591
- Effect of moderate alcohol intake on nocturnal sleep respiratory parameters in healthy middle-aged men. Environ Health Prev Med (2005) PMID: 21432159
- Sleep following alcohol intoxication in healthy, young adults: effects of sex and family history of alcoholism. Arnedt JT. Alcohol Clin Exp Res. 2011 May 10.1111/j.1530-0277.2010.01417.x. Epub 2011 Feb 15