Alcohol And Rem Sleep: A Troubling Relationship

Alcohol can have a detrimental effect on sleep quality, even in moderate amounts. While alcohol can help people fall asleep faster, it ultimately compromises sleep quality and quantity by causing disruptions later in the night.

Alcohol affects the sleep cycle by altering the four stages of sleep. Initially, it increases slow-wave sleep and suppresses REM sleep. However, later in the night, as alcohol levels drop, people experience more fragmented sleep with frequent awakenings. This is because alcohol inhibits REM sleep, which is considered the most mentally restorative phase of sleep.

Additionally, alcohol is a diuretic, increasing urine output and leading to more frequent urination during the night.

Research suggests that the negative impact of alcohol on sleep is similar for men and women and affects younger people more than older adults. To minimise the impact of alcohol on sleep, it is recommended to avoid alcohol at least three hours before bed.

Alcohol suppresses REM sleep, especially in the first half of the night

Research has shown that the effects of alcohol on REM sleep are dose-related. Low and moderate doses show no clear trend on REM sleep in the first half of the night, whereas high doses significantly reduce REM sleep in the initial part of sleep. Total REM sleep percentage decreases for the majority of studies at moderate and high doses, with no clear trend apparent at low doses. The onset of the first REM sleep period is significantly delayed at all doses and appears to be the most recognisable effect of alcohol on REM sleep.

The impact of alcohol on sleep can be both acute and chronic. Acute administration of large amounts of alcohol before sleep leads to decreased sleep onset latency and changes in sleep architecture early in the night, when blood alcohol levels are high, with subsequent disrupted, poor-quality sleep later in the night. Chronic alcohol abuse and dependence are associated with long-term sleep disturbances, lower slow-wave sleep, and more REM sleep than normal, which can last long into periods of abstinence and may play a role in relapse.

Alcohol increases urine output, causing more frequent bathroom trips

Alcohol is a diuretic, which means it increases urine output. This can cause more frequent bathroom trips during the night, interrupting your sleep.

Alcohol is initially sedating, but as it is metabolised, it becomes activating. This means that while you may fall asleep faster, you will experience more disrupted sleep in the second half of the night. As alcohol levels in your blood drop, your brain kicks into overdrive, causing you to toss and turn.

Alcohol also inhibits REM sleep, which is the most mentally restorative phase of sleep. This can lead to more vivid or stressful dreams, and you are more likely to remember them due to the fragmented nature of your sleep.

To minimise the impact of alcohol on your sleep, it is recommended to allow at least three hours between your last drink and bedtime. Drinking water alongside alcohol can also help to flush it out of your system.

Alcohol negatively impacts sleep quality, causing more disrupted sleep in the second half of the night

During the first half of the night, when blood alcohol levels are high, people tend to experience more slow-wave sleep and less REM sleep than usual. Slow-wave sleep, also known as deep sleep, is characterised by slow delta activity in the brain. REM sleep, on the other hand, is when most dreaming occurs and is considered the most mentally restorative phase of sleep.

Later in the night, once the body has metabolised the alcohol, people are likely to experience a rise in N1 sleep, the lightest stage of sleep, leading to more frequent wakings and fragmented sleep. This pattern of initial sleep augmentation followed by poor-quality sleep can lead to a vicious cycle where insomnia is self-treated with alcohol, resulting in further disrupted sleep and daytime sleepiness.

Research suggests that alcohol negatively impacts sleep quality regardless of consumption level. A 2018 study found that low alcohol intake reduced sleep quality by 9.3%, moderate alcohol intake by 24%, and heavy alcohol intake by nearly 40%. The study also showed that alcohol affected men and women similarly and that it had a more significant impact on younger people than older adults.

To minimise the negative impact of alcohol on sleep, it is recommended to allow at least three hours between the last drink and bedtime. Drinking water alongside alcohol and having drinks with meals can also help.

Alcohol increases the risk of snoring and sleep apnea

Alcohol is a relaxant that can worsen sleep apnea because it hinders the nervous system and the brain's response to breathing problems while asleep. It reduces the body's natural impulse to wake up when you can't breathe. With this arousal response diminished, an apnea event is prolonged. This reduces oxygen flow to the lungs, leaving you unrested in the morning.

Heavy drinking can increase the risk of prolonged apnea events in people with obstructive sleep apnea (OSA). Because of the sedative effects of alcohol, it may even trigger apnea events in people without OSA. Obstructive sleep apnea can be caused by mild to heavy drinking, according to studies, which were conducted on individuals who did not know they had the disorder.

Alcohol also increases the risk of snoring and sleep apnea by causing nasal congestion, making it harder to breathe through the nose. It can also lead to increased nasal congestion, especially when consumed in the evening or shortly before bed, as it raises blood alcohol levels during sleep.

The more alcohol a person drinks, the more it affects their overall health, sleep quality, and quantity. Older people are more affected by alcohol, so drinking before bed will further worsen their sleep apnea.

Alcohol disrupts the body's circadian rhythm

Alcohol can have a detrimental effect on the body's circadian rhythm, which is the 24-hour cycle that regulates important biological processes, including sleep.

Evidence suggests that alcohol consumption may decrease the body's sensitivity to cues such as daylight and darkness, which are essential triggers for shifts in body temperature and the secretion of the sleep hormone melatonin. These fluctuations are vital for maintaining a healthy sleep-wake cycle. When these cues are weakened or absent, a person may feel alert when they want to sleep and sleepy when they want to be awake.

In addition to altering sleep architecture, alcohol can interfere with circadian rhythms and contribute to sleep disorders. The effects of alcohol on sleep can be both acute and chronic, impacting heavy drinkers in the long term.

Alcohol's impact on sleep is complex and involves interactions between various neurotransmitter systems that regulate sleep. As a central nervous system depressant, alcohol initially acts as a sedative, helping individuals fall asleep faster. However, as the body metabolises alcohol, it can lead to disrupted and poor-quality sleep later in the night. This is because alcohol interferes with the normal sleep cycle, reducing REM sleep and increasing slow-wave sleep initially. Later in the night, once the body has metabolised the alcohol, individuals may experience more frequent awakenings and fragmented sleep.

The negative impact of alcohol on sleep is supported by research, which found that even light alcohol consumption can reduce sleep quality. The study analysed the sleep and alcohol habits of 4,098 adults and found that low alcohol intake reduced sleep quality by 9.3%, while moderate alcohol intake reduced sleep quality by 24%. Heavy alcohol intake reduced sleep quality by nearly 40%.

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