What Are the Effects of Alcohol on Sleep

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Two shaker and a champagne glass on the counter in a bar.

At a Glance

  • In contrast to widely held beliefs, alcohol has very few positive effects on sleep.
  • There are numerous negative effects to consuming alcohol before bedtime, including increased insomnia and a reduction in sleep quality
  • We discuss the scientific evidence regarding the effects of alcohol on sleep in relation to normal, healthy sleep patterns

All of the functions of sleep are not yet fully understood. What we do know, however, is it’s very important in terms of our physical and mental health, safety and our quality of life.

There are many different approaches to making sure people get good night’s sleep. Some ideas are based on scientific evidence; others are traditional remedies, or even urban myths.

Many people still hold true to the tradition of a nightcap – a little tipple before bedtime – to help improve their sleep.

However, research into the effects of alcohol on sleep suggests it may not be the best thing for you. If you are one of the people who indulge in alcohol in the belief that it will help you sleep, it is important to arm yourself with the facts about sleep and alcohol.

In this article, we discuss the relationship between alcohol and sleep and take a thorough look at the scientific evidence which describes what sleep is, the importance of sleep and how alcohol affects the body, with particular regard to the impact on sleep.

What Is Alcohol?

Essentially, alcohol, or ethanol, is a type of carbohydrate which is produced by yeast when it breaks down sugars without the presence of oxygen. This process is called fermentation, and is used in different ways by a number of manufacturers to produce the various different types of alcohol we see on our liquor store shelves.

How Does Alcohol Affect the Body?

Two wine glasses and a glass of wine in a living room.

According to the Centers for Disease Control and Prevention (CDC), alcohol depresses the central nervous system. After consuming alcohol, it is assimilated into the bloodstream from the digestive system.

Alcohol affects all of the organs in the body, and the effect of the alcohol depends on the amount and speed of alcohol consumption; how much food is in the stomach prior to drinking alcohol, our age, physical health and interaction between alcohol and any drugs – prescription or otherwise – are all factors on how alcohol affects and individual. (source)

Alcohol has many different effects on the various organs of the body:


– alcohol disrupts the communication pathways in the brain, changing the efficiency of the messages between different parts of the brain. This can decrease our coordination of movement, decrease our ability to think clearly and judge accurately as well as change our mood and behavior. (source)


– A high level of alcohol consumption has been shown to cause stretching and decreased elasticity of the heart muscle fibers, and has also been linked with irregular heartbeat. Alcohol also causes changes in our cardiovascular system that increases the risk of stroke, high blood pressure and heart attack.

A low to moderate level of consumption, however, has been linked with increased vascular health, and lower risk of coronary heart disease. Studies do note, however, that more research is needed to confirm that health benefits are a direct result of moderate alcohol intake, and observe that they may be linked to the type of alcohol consumed. (source)


– the liver is responsible for breaking down and disposing of alcohol, but can only deal with a little at a time. Consuming more alcohol than the liver can handle can lead to fatty liver disease, a form of alcohol-related hepatitis, liver fibrosis and cirrhosis of the liver. (source)


– essential for, among other functions, producing and secreting substances which facilitate digestion, and producing insulin to help balance blood sugar. Alcohol stimulates the pancreas to produce poisonous chemicals which can lead to pancreatitis; a condition where inflammation of in the pancreas leads to the breakdown of pancreatic tissue, resulting in tissue damage, bleeding, increased risk of infection and permanent damage to the pancreas. (source)

Immune system

– responsible for protecting the body against illness and infection, alcohol has been shown in research to increase the body’s susceptibility to diseases, including pneumonia and other respiratory problems, lead to increased systemic inflammation, increase the risk of some types of cancers, decrease the body’s ability to recover from infections and slow down wound healing. (source)

How Does Sleep Work?

Research indicates that sleep is actually a series of different phases which follow a specific pattern that recurs throughout the night. The cycle begins with a type of sleep called non-rapid eye movement (NREM), followed by rapid eye movement (REM) sleep. NREM has three distinct phases:

N1 – when you first close your eyes. For the first 10-15 minutes of sleep, you sleep very lightly and are very easily disturbed.

N2 – another phase of light sleep which is easily disturbed, this phase usually lasts for between ten and 25 minutes. The N2 phase is characterized by a decrease in heart rate and body temperature as your body prepares for deep sleep.

N3 – this is a deep sleep phase, where brain activity slows down – brain waves become slower and larger and you become less responsive to environmental disturbances. The N3 phase usually lasts for between 20 to 40 minutes.

Research indicates that we normally experience a further phase of N2 sleep before REM sleep begins. During the NREM sleep phase, the body begins to heal, repair and renew body tissue. The immune system also starts to strengthen.

REM sleep phases make up approximately 25 percent of our total sleep, and they become longer as the night progresses. This is a deep sleep phase where dreams occur. Throughout the night, sleep then continues in a cyclical pattern through the deeper stages of NREM and REM sleep. (source)

How Does Alcohol Affect Sleep?

Woman laying sleeplessly in her bed which is one of the effects of alcohol on sleep.

It’s true that alcohol does make us feel sleepy. Research studies have shown that alcohol significantly reduces sleep onset latency – the amount of time it takes us to fall asleep. It has also been shown to increase the quality and quantity of NREM when we first fall asleep after consuming alcohol. (source)

However, it does so by depressing the nervous system. The feelings of sleepiness that accompany alcohol consumption are actually related to the effects of alcohol on relaxing the muscles and its action of slowing down brain function.

This is not a natural way to achieve sleep, and works in direct contrast with the way our brain normally stimulates us to sleep. As a result, the overall quality of sleep we get after consuming alcohol is very poor, and this doesn’t help our bodies to rest and heal properly.

We know this because research studies have observed the effects of alcohol on the brain during sleep, and found that during the latter part of a night’s sleep after consuming alcohol, our normal sleep cycles are severely disrupted. (source)

Reduced REM Sleep

In particular, clinical trials have shown that alcohol consumption, even in low and moderate amounts, dramatically reduces the amount of REM sleep. One such study demonstrated that the first period of REM sleep after consuming alcohol is significantly delayed when compared with falling asleep after no alcohol. (source)

Other research has identified increased periods of light NREM sleep and waking from sleep during the second half of a night’s sleep. This is the time when, during normal sleep, our periods of REM sleep should be increasing. (source)

According to experts at the Sleep Association, this is thought to be due to the after effects of alcohol. As the alcohol in the body is metabolized while you sleep, and no longer affects the brain, the various systems in the brain “wake up”, and cause further disturbance to brain waves – sometimes to the point of causing waking.

While you sleep, the body starts to recognize the after effects of drinking alcohol, such as an increased need for sugar and water, increased acid in the digestive system and associated stomach irritation. These alcohol-related factors can also cause waking. The more we wake from sleep, the more our normal sleep cycles are disrupted and the poorer the quality of sleep we get. (source)

Brain Waves and Alcohol

Scientists have discovered and recorded many different types of brain waves – types of electrical activity – that are produced by the brain. Brain waves changes according to our activities.

Of the six main types of brain waves, beta brain waves are the most common when we are awake and active, with alpha brain waves being produced during quiet, calm wakefulness, and theta brain waves occurring in deep meditative states.

When we sleep, the brain normally produces theta and delta brain waves of slow rhythmic electrical activity.

Many research studies have investigated the effects of alcohol consumption on brain waves produced when we sleep. One such study found that there was an increased amount of alpha waves produced during sleep compared to participants who had not consumed alcohol.

The research concluded that the alpha waves cancel out the restorative power of the delta waves produced, suggesting a much poorer quality sleep with less restorative capabilities after consuming even a small amount of alcohol. (source)

The Effect of Alcohol on Sleep Apnea

Sleep apnea is a condition in which breathing frequently stops during sleep. There are various different types of sleep apnea, but in all cases the airways become blocked during sleep. This is usually caused by the effect of gravity and the relaxation of the tongue and upper respiratory tissues during sleep.

When the brain receives signals that the respiratory obstruction results in dangerously low oxygen levels, it stimulates movement which facilitates release of the obstruction. This can happen on numerous occasions during a night’s sleep, and results in poor quality sleep which leaves the sufferer feeling tired and groggy the next day.

Alcohol has been found to significantly increase the incidence of sleep apnea, in terms of the duration of the obstruction and the number of times the airway becomes blocked.

This is thought to be due to the muscle relaxant effects of alcohol and the depression of brain function; the alcohol increases the amount of time taken by the brain to recognize and manage the obstruction. (source)

Why Is Sleep Important?

Woman sleeping on her stomach in her bed between her sheets.

Sleep has many important functions that have been identified by research. Sleep has a considerable restorative impact on the brain, supporting optimal brain function, helping us to consolidate memory patterns and learning, improving problem solving ability, focus and concentration skills.

Research indicates that not only is sleep essential for improving our ability to retain information, but when we receive inadequate or poor quality sleep we are unable to learn and acquire new skills effectively. (source)

Adequate sleep can also improve our social skills, aid our decision making processes, and can significantly affect mood. Research indicates that consistent high quality sleep patterns reduce irritability, anxiety and can reduce the risk of suffering depression, as well as reducing the risk of suicide.

Good quality sleep has also been shown to support growth and development, aid body tissue repair and boost immune system function, as well as reducing the risk of many serious health conditions, including obesity, heart disease, stroke and diabetes.

In addition, inadequate and poor quality sleep, including as a result of alcohol consumption can have a serious negative impact on the ability to make good judgments. This has been shown to increase the risk of having or causing an accident or injury, particularly in individuals who operate machinery or vehicles. (source)

So sleep affects every part of our lives. According to the National Heart, Lung and Blood Institute, the amount of sleep we need varies with age. The average adult needs between seven and nine hours of sleep each night. (source)

After Effects of Alcohol and Alcohol-Induced Sleep

Consuming alcohol before sleep can cause a significant reduction in the amount of sleep as well as reducing the quality of sleep. Research has shown that even one night with inadequate sleep can impair performance when completing cognitive tasks the following day.

Further clinical trials have evaluated the effect of alcohol on performance. One study, using airline pilots as participants, created a blood alcohol level of 100 mg per liter of blood – twice the United Nations’ recommended legal driving limit.

Researchers then tested the pilot’s performance on a flight simulator the day after consuming the alcohol. The results showed a significant impairment in performance indicators compared to when they were tested after consuming no alcohol. (source)

Sleep Solutions

Woman in sweater laying on her back in her bed while holding a book.

If you are having trouble sleeping, especially if you feel lack of sleep is making you feel tired during the day, it’s worth discussing this with your doctor.

There are many ways to improve your amount and quality of sleep, but alcohol is not one of them. Sleep habits and our sleeping environment can have a significant effect on our sleep, so if you want to improve your sleep, try the following:

Avoid alcohol and stimulants such as caffeine and nicotine a few hours before bed.

Create a relaxing environment in your bedroom – consider low level lighting, and leave electronic devices outside the bedroom.

Keep the temperature in your bedroom cool but comfortable.

Take regular gentle exercise, but not too late in the evening. Leave at least a few hours between exercise and bedtime.

Prepare for bedtime by switching off the TV and reading a book (but not a book that keeps you on the edge of your seat!) or listen to some relaxing music.

Some people find that drinking warm milk, or a herbal warm drink, such as chamomile tea, helps them to relax before bed, but don’t be tempted to add sugar. Having sugar before bedtime may contribute to difficulty sleeping.

Plan regular sleeping schedule. Sleeping and waking at the same time every day helps your body to anticipate that it’s time to sleep.

Final Thoughts

When it comes down to it, alcohol is a drug, and although it is widely acceptable to use alcohol in many societies, it does have adverse effects on the body. Alcohol can increase the risk of many serious health conditions, and also has a huge effect on our sleep.

Although alcohol might help to decrease the time it takes to fall asleep, it can decrease our total sleep time and cause frequent waking as the body deals with the after effects of consuming alcohol.

In terms of sleep quality, alcohol causes us to spend more time in lighter sleep phases, and less time in the deeper sleep phases, which are the periods in our sleep cycle which are most refreshing and restorative.

As a result of a reduction in sleep quantity and quality, research has shown that not only does the risk of poor physical and mental health increase, the after effects of consuming alcohol before sleep can be seen in terms of poor performance the following day.

People who are having trouble sleeping would be well advised to avoid alcohol at bedtime. Instead there are a variety different ideas which can help to improve sleep habits.

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