Alcohol consumption at almost any level can cause sleep disturbance and induce sleep disorders. Drinking alcohol can disrupt the structure and duration of sleep states, alter total sleep time, and affect the time required to fall asleep.﻿﻿

While researchers don't fully understand all the complex functions that occur in the body during sleep, we do know that lack of sleep is linked to serious problems including increased risk of depressive disorders, heart disease, and other health problems.

We also know that excessive daytime sleepiness, resulting from a lack of sleep, is linked to impaired social and occupational function, memory deficits, and risk of having a vehicle crash.﻿﻿

What Is a Normal Sleep Pattern?

Normal sleep consists of two alternating states of sleep in which brain waves exhibit different types of activity:

Slow-wave sleep (SWS) , during which the brain ways are very slow, is deep, restful sleep and usually makes up about 75% of a night's sleep

, during which the brain ways are very slow, is deep, restful sleep and usually makes up about 75% of a night's sleep Rapid eye movement sleep (REM), during which the eyes exhibit rapid movements, is less restful, and is usually associated with dreaming (REM occurs periodically during sleep time and makes up about 25% of sleep time for young adults; episodes of REM sleep can recur about 90 minutes and last from 5–30 minutes at a time.)

Additionally, research has identified a transitional light sleep stage that occurs at intervals during the sleep period.

Science does not know what function REM sleep performs for the body, but it seems to be required for restoration. Some studies have found that when laboratory rats are deprived of REM sleep it can result in death within a few weeks.

How the Brain Controls Sleep

It was originally thought that sleep was the result of decreased activity in the brain's systems that maintained wakefulness, but research has shown that sleep is an active process of the brain, controlled by nerve centers in the lower brain stem.

Some of these nerve stems produce serotonin, a chemical that has been linked to the onset of sleep and with the regulation of slow-wave sleep. Other nerve cells produce norepinephrine, which has been found to regulate REM sleep and facilitate arousal.

It is not known exactly how these and other chemicals in the brain interact to control sleep, but we do know that alcohol consumption alters the function of these chemical messengers and therefore alters sleep patterns.

Alcohol and Sleep

Many people suffering from insomnia will take a drink before bedtime to help them fall asleep. After an initial stimulating effect, alcohol's sedating effects can reduce the time required to fall asleep.

But alcohol's effects do not end there. Research shows that alcohol consumed within an hour of bedtime will disrupt sleep in the second half of the sleep period, causing the person to sleep fitfully—awakening from dreams and not being able to get back to sleep easily.

Over time, the drink before bedtime works even less effectively. With continued consumption, studies found alcohol's sleep-inducing effects decrease, while its sleep disturbance effects increase.

This is particularly true for elderly adults because drinking produces higher levels of alcohol in their blood and brain compared to younger drinkers. Consequently, older adults who have a drink before bedtime can experience an increased risk for falls and injuries if they get up and walk during the night.

'Happy Hour' Drinks

Studies have found that alcohol consumed even six hours before bedtime can increase wakefulness during the second half of sleep, even though the alcohol consumed has already been eliminated from the body.﻿﻿

Researchers believe the alcohol causes a long-lasting change in how the body regulates sleep.

Sleep Disorders

Chronic alcohol use appears to be linked to an increased risk for sleep apnea, especially among drinkers who snore.

Obstructive sleep apnea is a disorder in which the upper air passage narrows or closes during sleep, causing interrupted breathing. When this happens, the person will awaken, resume breathing, and then return to sleep. Incidents of apnea followed by awakening can occur hundreds of times during the night, significantly reducing sleep time.

Furthermore, drinking moderate to high amounts of alcohol prior to sleep can narrow the air passage, causing episodes of apnea in persons who normally do not exhibit sleep apnea symptoms.

Why is this effect of alcohol on apnea important? Sleep apnea sufferers who drink two or more drinks a day are five times more likely to be involved in a fatigue-related traffic crash than those who do not drink.

Research has linked the combination of sleep apnea, snoring, and alcohol consumption with an increased risk of heart attack, arrhythmia, stroke, and sudden death.

Aging

When people get older, they naturally experience a decrease in slow-wave sleep and an increase in nighttime wakefulness. Research has found that people over 65 often awake three or more times during the night.﻿﻿

This leads to sleep that is less restful and restorative and can encourage the use of alcohol to try to increase sleep. The results, however, is an increase in alcohol-related sleep disturbances for older adults.

Alcohol Use Disorder and Sleep

For those with severe alcohol use disorder, sleep disturbances may also include the following:

Daytime fatigue

Decrease in quality sleep

Frequent awakenings

Longer time required to fall asleep

It seems reasonable to think that people with an alcohol use disorder who quit drinking would return to normal sleep patterns, but actually, the sudden cessation of alcohol consumption can result in alcohol withdrawal syndrome, which can produce pronounced insomnia and persistent sleep fragmentation.

Lack of sleep is one of the most common symptoms mentioned by those who are going through alcohol withdrawal after they stop drinking.

Alcohol withdrawal syndrome can lead to the following:

Increased REM sleep related to withdrawal hallucinations

Reduction in restful sleep

Sleep consisting of brief periods of REM sleep

Sleep interrupted by numerous awakenings

Recovery, Sleep, and Relapse

After the withdrawal symptoms subside, people with an alcohol use disorder can experience some improvement in sleep patterns, but for some, normal sleep patterns may never return, even after years of sobriety.

Studies have found that people in recovering tend to sleep poorly, have less slow-wave sleep, and increased wakefulness, resulting in less restorative sleep and daytime fatigue.﻿﻿

Ironically, if the person in recovery returns to heavy drinking, their slow-wave sleep will increase and their nighttime wakefulness will decrease, at least initially. This mistaken impression that alcohol consumption improves sleep is a major reason that many people with an alcohol use disorder relapse. The relief they get, however, is only temporary.

As they continue to drink, their sleep patterns soon become disrupted again. The idea that alcohol consumption improves sleep is, in reality, only a myth.