Alcohol's Effect On Rem Sleep: What You Need To Know

Alcohol has a complex relationship with sleep. While it can help people fall asleep faster, it often leads to disrupted sleep and a feeling of fatigue the next day. The more alcohol consumed, the more negative the impact on sleep.

Alcohol alters sleep stages, increasing deep sleep initially and decreasing REM sleep. This can have detrimental effects on memory consolidation and other cognitive processes. As the body metabolises alcohol, people tend to experience more light sleep and frequent awakenings, resulting in overall poorer sleep.

Alcohol also affects levels of adenosine, a chemical that induces sleep. While increased adenosine helps people fall asleep faster, it can lead to more disrupted sleep later in the night.

Additionally, alcohol consumption is linked to increased snoring and symptoms of obstructive sleep apnea, a disorder characterised by frequent breathing cessations during sleep.

Overall, while moderate alcohol consumption may not significantly impact sleep, heavier drinking can lead to a reduction in sleep quality by up to 40%. Therefore, it is generally recommended to avoid alcohol close to bedtime to ensure a good night's rest.

Alcohol and sleep architecture

Alcohol is a sedative that interacts with several neurotransmitter systems that are important in regulating sleep. It is rapidly absorbed into the bloodstream and remains there until metabolised by the liver, typically at a rate of about one drink per hour. When consumed before bed, alcohol leads to alterations in sleep architecture, that is, how the body cycles through the four stages of sleep.

The typical sleep cycle begins with three non-rapid eye movement (NREM) stages of sleep and ends with rapid eye movement (REM) sleep. During sleep, the body cycles through all these stages every 90 to 120 minutes, with NREM sleep dominating the first part of the night and REM increasing during the second part. Each stage is necessary for sleep to be refreshing and for vital processes like learning and memory consolidation to occur.

When going to bed with alcohol in the system, one is likely to experience more N3 sleep, or "deep sleep", and less REM sleep than usual, at least initially. Later in the night, once the body has metabolised the alcohol, one is likely to experience a rise in N1 sleep, the lightest stage of sleep, leading to frequent wakings and fragmented, low-quality sleep.

Alcohol's effects on sleep can be both acute, that is, immediate, and chronic, affecting heavy drinkers in the long term. Acute administration of large amounts of alcohol prior to 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.

Alcohol abuse and dependence are associated with chronic sleep disturbances, lower slow-wave sleep, and more REM sleep than normal, lasting long into periods of abstinence and possibly playing a role in relapse. Sleep studies of abstinent alcoholics typically show a pattern of sleep disturbance with increased wakefulness, consistent with self-reports of persistent sleep disturbance common in this population.

Alcohol increases levels of adenosine, a key component of the homeostatic drive, responsible for keeping the body balanced and regulating the sleep-wake cycle. After a few drinks, increased adenosine levels send one into a deep sleep. However, once the body realises it has had too much slow-wave sleep, the homeostatic drive compensates by allowing less deep sleep in the second half of the night. Frequent disruptions to the natural sleep cycle may alter the homeostatic drive in a more permanent way.

Alcohol may also exert effects on sleep by influencing the circadian rhythm, which is responsible for keeping the body anchored to a 24-hour cycle. As part of this cycle, the body releases melatonin to prepare for sleep in the evening. Older studies have found that drinking alcohol before bedtime lowers melatonin levels and interferes with core body temperatures, impacting sleep quality.

Alcohol is also a diuretic, increasing urine output, which can lead to frequent awakenings to urinate. Moderate amounts of alcohol, especially wine and spirits, have an early diuretic effect, especially in the elderly. It is unclear whether the urge to urinate wakes one up or if one is just more attuned to their body in the second half of the night due to more fitful sleep.

In summary, while alcohol may help one fall asleep faster, it ultimately has a negative impact on sleep quality. It is recommended to avoid alcohol at least three hours before bed to minimise its disruptive effects on sleep.

Alcohol and adenosine

Alcohol initially acts as a sedative, increasing the proportion of deep sleep at the beginning of the night. However, as the alcohol's effects start to wear off, the body spends more time in light sleep, which is not as sound and may lead to more nighttime awakenings. As a result of these frequent awakenings, people tend to clock fewer hours of sleep after drinking alcohol.

Adenosine is a neuromodulator, a chemical that modifies brain function and has been linked to several of alcohol's acute and chronic effects. Alcohol interferes with the function of the adenosine system, affecting the function of adenosine-carrying nucleoside transporters and, in turn, altering the levels of small signalling molecules in the cells.

In cell cultures, acute exposure to alcohol inhibits adenosine reuptake via the equilibrative nucleoside transporter type 1 (ENT1), leading to increased extracellular concentrations of adenosine. Conversely, chronic exposure to alcohol downregulates the expression of ENT1, so that alcohol-mediated inhibition of ENT1 is reduced and extracellular adenosine decreases.

In vivo rodent studies have shown that adenosine is a key player in the behavioural effects of alcohol, such as the promotion of sleep and the impairment of motor movements. For example, a recent study found that the sleep-promoting effects of acute alcohol result from an adenosine A1 receptor-mediated inhibition of orexin neurons in the hypothalamus. These neurons are known to maintain wakefulness when activated, whereas a loss of orexin neurotransmission in the hypothalamus promotes sleep and can cause narcolepsy.

Moreover, there is increasing evidence that the motor-impairing effects of alcohol are mediated by A1 receptors in several brain areas, including the cerebellum, striatum, and cortex.

Alcohol and REM sleep

Alcohol is a sedative that interacts with several neurotransmitter systems that are important in regulating sleep. While alcohol can help people fall asleep faster, it ultimately has a negative impact on sleep quality. Even in moderate amounts, alcohol consumed in the hours before bedtime can disrupt sleep and leave people feeling tired the next day.

Alcohol increases levels of adenosine, a chemical in the brain that acts as a sleep-inducer. This increase in adenosine sends people into a deep sleep. However, once the body realises it has had too much slow-wave sleep, it compensates by allowing less deep sleep in the second half of the night. This can lead to a pattern of initial sleep augmentation followed by a period of poor-quality sleep.

Alcohol also inhibits REM sleep, which is often considered the most mentally restorative phase of sleep. REM sleep is when most dreaming occurs. As alcohol levels drop, people may experience more vivid or stressful dreams and are more likely to remember them due to frequent awakenings.

Alcohol and Sleep by the Numbers

A 2018 study found that alcohol had significant effects on sleep quality, regardless of whether consumption was light, moderate, or heavy. The study analysed the sleep and alcohol habits of 4,098 adults and found that:

• Low alcohol intake reduced sleep quality by 9.3%
• Moderate alcohol intake (defined as two drinks per day for men and one for women) reduced sleep quality by 24%
• Heavy alcohol intake reduced sleep quality by nearly 40%

The study also showed that alcohol affected men and women similarly and that it impacted the sleep of younger people more than older adults.

Alcohol and sleep disorders

Alcohol is a depressant that can help you fall asleep faster. However, its effects wear off a few hours later as your body tries to eliminate it from your system. According to the National Sleep Foundation, the production of adenosine, a sleep-inducing chemical in the brain, increases when drinking alcohol, allowing you to fall asleep quickly. However, this chemical quickly subsides, making you more likely to wake up during the night.

Alcohol inhibits REM sleep, considered the most mentally restorative sleep phase. It also affects the slow-wave sleep patterns called delta activity and turns on alpha activity, which indicates wakefulness with eyes closed. Experiencing these two brain activities simultaneously inhibits quality rest.

A 2018 study found that alcohol significantly affected sleep quality, with higher consumption causing more disruption. Low alcohol intake reduced sleep quality by 9.3%, moderate intake by 24%, and heavy intake by nearly 40%. The study also showed that alcohol affected men and women similarly and that it impacted younger people more than older adults.

Alcohol also increases the risk of snoring and symptoms of obstructive sleep apnea, a disorder characterised by short and frequent breathing cessations during sleep. It can worsen existing cases of sleep apnea and increase the risk of developing it.

Additionally, alcohol interferes with the circadian rhythm, the biological pattern that operates on a 24-hour clock. It may decrease the body's sensitivity to cues like daylight and darkness, which trigger shifts in body temperature and the release of the sleep hormone melatonin, vital for the sleep-wake cycle.

Heavy alcohol use can contribute to insomnia, a disorder characterised by difficulty falling and staying asleep. Conversely, people with insomnia have an increased risk of developing alcohol use disorder, as they may turn to alcohol as a sleep aid.

Alcohol and sleep tips

How Alcohol Affects Sleep

Alcohol is a sedative that interacts with several neurotransmitter systems that regulate sleep. It can cause a shorter overall sleep time and disrupted sleep, leading to next-day fatigue and sleepiness. The more alcohol you drink, the greater the negative effects on your sleep.

Alcohol Alters Sleep Stages

During a normal night of sleep, we cycle through periods of light sleep, deep sleep, and rapid eye movement (REM) sleep. Each sleep stage plays an essential function, but deep sleep and REM sleep are considered the most important stages for physical and mental restoration.

Alcohol initially acts as a sedative, increasing the proportion of deep sleep at the beginning of the night. However, as the alcohol’s effects start to wear off, the body spends more time in light sleep, which is not as sound and may lead to more nighttime awakenings. As a result of these frequent awakenings, people tend to clock fewer hours of sleep after drinking alcohol.

Studies have found conflicting information about how alcohol affects REM sleep. Alcohol appears to consistently delay the first REM sleep episode, and higher doses of alcohol appear to reduce the total amount of REM sleep. Suppressing REM sleep can have detrimental consequences for memory consolidation and other cognitive processes.

Tips for Drinking and Sleeping Responsibly

• Allow at least three hours between your last drink and bedtime.
• Drink water along with alcohol to help flush it out of your system.
• Drink alcohol while eating a meal—since you’re likely eating a few hours before bed, this is a good way to keep drinking in check.
• Avoid alcohol if you’re taking sleeping pills—both are depressants, and in combination, they can make it very hard for a person to breathe while sleeping, which can be dangerous.

Frequently asked questions