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Alcohol is a central nervous system depressant that causes brain activity to slow down. Alcohol has sedative effects that can induce feelings of relaxation and sleepiness, but the consumption of alcohol – especially in excess – has been linked to poor sleep quality and duration. People with alcohol use disorders commonly experience insomnia symptoms. Studies have shown that alcohol use can exacerbate the symptoms of sleep apnea.
Drinking in moderation is generally considered safe but every individual reacts differently to alcohol. As a result, alcohol’s impact on sleep largely depends on the individual.
How Does Alcohol Affect Sleep?
After a person consumes alcohol, the substance is absorbed into their bloodstream from the stomach and small intestine. Enzymes in the liver eventually metabolize the alcohol, but because this is a fairly slow process, excess alcohol will continue to circulate throughout the body. The effects of alcohol largely depend on the consumer. Important factors include the amount of alcohol and how quickly it is consumed, as well as the person’s age, sex, body type, and physical shape.
The relationship between alcohol and sleep has been studied since the 1930s, yet many aspects of this relationship are still unknown. Research has shown sleepers who drink large amounts of alcohol before going to bed are often prone to delayed sleep onset, meaning they need more time to fall asleep. As liver enzymes metabolize the alcohol during their night and the blood alcohol level decreases, these individuals are also more likely to experience sleep disruptions and decreases in sleep quality.
To understand how alcohol impacts sleep, it’s important to discuss different stages of the human sleep cycle. A normal sleep cycle consists of four different stages: three non-rapid eye movement (NREM) stages and one rapid eye movement (REM) stage.
- Stage 1 (NREM): This initial stage is essentially the transition period between wakefulness and sleep, during which the body will begin to shut down. The sleeper’s heart beat, breathing, and eye movements start to slow down and their muscles will relax. Brain activity also begins to decrease, as well. This phase is also known as light sleep.
- Stage 2 (NREM): The sleeper’s heartbeat and breathing rates continue to slow down as they progress toward deeper sleep. Their body temperature will also decrease and the eyes become still. Stage 2 is usually the longest of the four sleep cycle stages.
- Stages 3 (NREM): Heartbeat, breathing rates, and brain activity all reach their lowest levels of the sleep cycle. Eye movements cease and the muscles are totally relaxed. This stage is known as slow-wave sleep.
- REM: REM sleep kicks in about 90 minutes after the individual initially falls asleep. Eye movements will restart and the sleeper’s breathing rate and heartbeat will quicken. Dreaming mostly takes place during REM sleep. This stage is also thought to play a role in memory consolidation.
These four NREM and REM stages repeat in cyclical fashion throughout the night. Each cycle should last roughly 90-120 minutes, resulting in four to five cycles for every eight hours of sleep. For the first one or two cycles, NREM slow-wave sleep is dominant, whereas REM sleep typically lasts no longer than 10 minutes. For later cycles, these roles will flip and REM will become more dominant, sometimes lasting 40 minutes or longer without interruption; NREM sleep will essentially cease during these cycles.
Drinking alcohol before bed can add to the suppression of REM sleep during the first two cycles. Since alcohol is a sedative, sleep onset is often shorter for drinkers and some fall into deep sleep rather quickly. As the night progresses, this can create an imbalance between slow-wave sleep and REM sleep, resulting in less of the latter and more of the former. This decreases overall sleep quality, which can result in shorter sleep duration and more sleep disruptions.
Alcohol and Insomnia
Insomnia, the most common sleep disorder, is defined as “a persistent difficulty with sleep initiation, duration, consolidation, or quality.” Insomnia occurs despite the opportunity and desire to sleep, and leads to excessive daytime sleepiness and other negative effects.
Since alcohol can reduce REM sleep and cause sleep disruptions, people who drink before bed often experience insomnia symptoms and feel excessively sleepy the following day. This can lead them into a vicious cycle that consists of self-medicating with alcohol in order to fall asleep, consuming caffeine and other stimulants during the day to stay awake, and then using alcohol as a sedative to offset the effects of these stimulants.
Binge-drinking – consuming an excessive amount of alcohol in a short period of time that results in a blood alcohol level of 0.08% or higher – can be particularly detrimental to sleep quality. In recent studies, people who took part in binge-drinking on a weekly basis were significantly more likely to have trouble falling and staying asleep. These findings were true for both men and women. Similar trends were observed in adolescents and young adults, as well as middle-aged and older adults.
Researchers have noted a link between long-term alcohol abuse and chronic sleep problems. People can develop a tolerance for alcohol rather quickly, leading them to drink more before bed in order to initiate sleep. Those who have been diagnosed with alcohol use disorders frequently report insomnia symptoms.
Alcohol and Sleep Apnea
Sleep apnea is a disorder characterized by abnormal breathing and temporary loss of breath during sleep. These lapses in breathing can in turn cause sleep disruptions and decrease sleep quality. Obstructive sleep apnea (OSA) occurs due to physical blockages in the back of the throat, while central sleep apnea (CSA) occurs because the brain cannot properly signal the muscles that control breathing.
During apnea-related breathing episodes – which can occur throughout the night – the sleeper may make choking noises. People with sleep apnea are also prone to loud, disruptive snoring. Some studies have suggested that alcohol contributes to sleep apnea because it causes the throat muscles to relax, which in turn creates more resistance during breathing. This can exacerbate OSA symptoms and lead to disruptive breathing episodes, as well as heavier snoring. Additionally, consuming just one serving of alcohol before bed can lead to OSA and heavy snoring even for people who have not been diagnosed with sleep apnea.
The relationship between sleep apnea and alcohol has been researched somewhat extensively. The general consensus based on various studies is that consuming alcohol increases the risk of sleep apnea by 25%.
Alcohol and Sleep FAQ
Does Alcohol Help You Sleep?
Alcohol may aid with sleep onset due to its sedative properties, allowing you to fall asleep more quickly. However, people who drink before bed often experience disruptions later in their sleep cycle as liver enzymes metabolize alcohol. This can also lead to excessive daytime sleepiness and other issues the following day. Furthermore, drinking to fall asleep can build a tolerance, forcing you to consume more alcohol each successive night in order to experience the sedative effects.
Does Alcohol Affect Men and Women Differently?
On average, women exhibit signs of intoxication earlier and with lower doses of alcohol than men. This can mostly be attributed to two factors. First, women tend to weigh less than men and those with lower body weights often become intoxicated more quickly. Most women also have a lower amount of water in their bodies than men. Alcohol circulates through water in the body, so women are more likely to have higher blood alcohol concentrations than men after consuming the same amount of alcohol.
What Is the Difference Between Moderate Drinking and Heavy Drinking?
Definitions vary by source, but the following measurements are generally considered to constitute a single serving of alcohol:
- 12 ounces of beer with 5% alcohol content
- 5 ounces of wine with 12% alcohol content
- 1 ounce of liquor or distilled spirits with 40% alcohol content
Moderate drinking is loosely defined as up to two drinks per day for men and one drink per day for women. Heavy drinking means more than 15 drinks per week for men and more than eight drinks per week for women.
Will a Small Amount of Alcohol Affect My Sleep?
Drinking to excess will probably have a more negative impact on sleep than light or moderate alcohol consumption. However, since the effects of alcohol are different from person to person, even small amounts of alcohol can reduce sleep quality for some people.
One 2018 study compared sleep quality among subjects who consumed different amounts of alcohol. The findings are as follows:
- Low amounts of alcohol (fewer than two servings per day for men or one serving per day for women) decreased sleep quality by 9.3%.
- Moderate amounts of alcohol (two servings per day for men or one serving per day for women) decreased sleep quality by 24%.
- High amounts of alcohol (more than two servings per day for men or one serving per day for women) decreased sleep quality by 39.2%.
When Should I Stop Drinking Prior To Bed To Minimize Sleep Disruption?
To reduce the risk of sleep disruptions, you should stop drinking alcohol at least four hours before bedtime.
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