Nah, a beer will make you sleep, but not well. A post on alcohol and sleep quality

Alcohol is widely consumed and for many reasons, including its potential to aid sleep. Sort of aid sleep that is.

Alcohol is known for its sedative effects, often helping people fall asleep faster. However, while alcohol may initially assist in sleep onset, it can cause sleep disruptions throughout the night.

Its effects on sleep are complex, and the timing, dosage, and frequency of consumption may all influence the outcomes.

A group of researchers have reviewed how alcohol affects sleep. The research focuses on parameters, such as sleep onset latency (the time it takes to fall asleep), wake after sleep onset and the overall sleep architecture, including the amount of the different sleep stages.

And the outcome is pretty interesting - also for us who enjoy a glass of wine in the evening ...

First a bit about the natural sleep

Sleep pressure is the natural drive to sleep that builds up the longer you stay awake. It’s driven by a chemical called adenosine, which accumulates in the brain during waking hours, making you feel sleepier as time goes on.

Once you sleep, adenosine levels decrease, reducing sleep pressure and helping you wake up refreshed

Sleep has different stages that repeat in cycles throughout the night. Stage 1, the lightest sleep, where brain activity begins to slow. Stage 2 features brain waves in bursts of activity and is linked to memory processing. Stage 3 is called deep sleep and is critical for physical and mental recovery. 

After the deep sleep comes a stage of REM sleep where your brain is very active. This is the sleep stage where you dream.

The full sleep cycle lasts about 90 minutes and repeats multiple times per night.

Alcohol and sleep onset

One of the most notable effects of alcohol is its ability to reduce sleep onset latency, meaning it helps individuals fall asleep faster.

Studies have shown that alcohol, particularly in low-to-moderate doses, can shorten the time taken to fall asleep. This is because alcohol boost the action of adenosine, the neurotransmitter that promotes sleep.

However, this effect is dose-dependent and varies between individuals. While alcohol may help some fall asleep faster, it can also disrupt sleep later in the night, particularly in terms of the overall sleep architecture.

Wake after sleep onset

Refers to the amount of time spent awake during the night after initially falling asleep.

Alcohol consumption has been shown to increase the time awake during the night, meaning individuals who drink alcohol in th evening, may fall a sleep quicker, but experience more frequent awakenings throughout the night.

There is no clear dose-response relationship between alcohol consumption and time awake at night. This suggests that the amount of alcohol consumed does not necessarily predict how much time an individual will spend awake during the night. So, its more like, alcohol whatever dose will disturb sleep.

One of the reasons alcohol may wake you up at night is its diuretic effect. Alcohol increases urine production, which can lead to individuals waking up more frequently to use the bathroom.

Additionally, alcohol’s effect on the body’s sleep pressure (the need for sleep) diminishes as the night progresses. This could lead to increased arousal and more frequent awakenings.

Alcohol’s effect on sleep architecture

Sleep architecture refers to thedistribution of different sleep stages during the night. Alcohol’s effects on sleep architecture are complex and vary based on the dose consumed.

Stage 3 deep sleep: Alcohol has a mixed effect on deep sleep. Some studies report that alcohol increases it during the first few hours of sleep. Larger doses appear to enhance deep sleep in the early part of the night. But, as alcohol is metabolized, the proportion of lighter sleep stages 1 and 2 increases.

This pattern suggests that alcohol initially promotes deeper sleep but later shifts the individual into lighter, less restorative sleep stages.

REM sleep: REM sleep is crucial for memory consolidation, emotional regulation, and cognitive function. Alcohol consistently disrupts REM sleep.
At lower doses, alcohol can delay the onset of the first REM sleep, and at higher doses, it significantly reduces the total amount of REM sleep.

The reduction in REM sleep is especially prominent in the latter half of the night when alcohol has been metabolized and acetaldehyde (a metabolite of alcohol) accumulates in the bloodstream.

This disruption of REM sleep can lead to impaired cognitive function and is just plain unhealthy.

But it feels like I sleep better!

Despite the objective findings of alcohol's disruptive effects on sleep, subjective reports of sleep quality and time spent asleep are often inconsistent.

In particular, while alcohol might reduce the perception of sleep onset latency, it does not always result in better quality or more restorative sleep.

Interestingly, alcohol's effects on sleep quality may be subjective, meaning that people may feel they sleep better due to the initial sedative effects of alcohol, but objective measures show otherwise.

Sex differences in alcohol's effects on sleep

The review did not provide strong evidence on the influence of sex on alcohol’s effects on sleep.

However, given the physiological differences between males and females, it is plausible that alcohol may affect the sleep men and women differently.

For instance, women generally have lower alcohol dehydrogenase activity (the enzyme that metabolizes alcohol) and lower total body water, which may result in higher blood alcohol concentrations for the same dose.

Research into these sex differences is still limited, and further investigation is needed to understand how hormonal changes impact alcohol-induced sleep disturbances.

In the long run

Although alcohol may help some individuals fall asleep faster, it is not a reliable or healthy long-term solution for improving sleep, as the long-term effects of alcohol consumption on sleep quality are generally negative.

Regular alcohol use can lead to a reduction in the important REM sleep and disrupt the overall sleep architecture, which may impair cognitive function and emotional regulation over time.

From a practical standpoint, it is therefore a good idea consider the potential negative effects of alcohol on sleep before using it as a sleep aid.

And for all of us to be mindful of alcohol consumption close to bedtime.

About the scientific paper:

First author: Carissa Gardiner, Australia
Published: Sleep Medicine Reviews, December 2024
Link to paper: https://www.sciencedirect.com/science/article/pii/S1087079224001345

Alcohol and Sleep: Dose-Dependent Effects on Sleep Architecture, Efficiency, and Quality

Alcohol is a widely consumed substance with complex effects on sleep. While alcohol may promote sleep initiation, its impact on overall sleep quality is multifaceted, and its effects are heavily dose-dependent. This systematic review and meta-analysis examined the effects of alcohol on various sleep parameters, including sleep onset latency, wake after sleep onset (WASO), sleep efficiency, and the disruption of sleep architecture, particularly in relation to rapid eye movement (REM) and non-rapid eye movement (NREM) sleep stages.

Alcohol and Sleep Onset Latency

Alcohol has a well-established effect on reducing sleep onset latency, meaning it can help individuals fall asleep more quickly. This effect is primarily due to alcohol’s ability to increase adenosine activity, a neurotransmitter associated with sleep promotion. Alcohol-induced sleep onset facilitation is dose-dependent, with low-to-moderate doses of alcohol having the most significant effect on sleep latency. However, this initial benefit is often followed by disruptions in sleep architecture during the course of the night, particularly as alcohol is metabolized.

Wake After Sleep Onset (WASO)

WASO refers to the total duration of wakefulness during the night after initially falling asleep. The impact of alcohol on WASO is variable and does not show a consistent dose-response relationship. Some studies indicate that alcohol consumption increases the frequency and duration of awakenings during the night, which could be attributed to the diuretic effects of alcohol or the diminishing effect of alcohol on sleep pressure. As alcohol’s sedative effects wear off, individuals may experience increased wakefulness or lighter sleep stages, contributing to higher WASO. However, the timing of alcohol intake and the dose consumed may modify this effect.

Sleep Efficiency

Sleep efficiency is defined as the proportion of time spent asleep relative to the total time spent in bed. It is a critical indicator of sleep quality. Alcohol’s effects on sleep efficiency vary across studies. In general, higher alcohol doses are associated with a decrease in sleep efficiency, suggesting that alcohol may cause fragmented sleep, despite an extended total sleep duration. In contrast, some studies suggest that low doses of alcohol might improve sleep efficiency by reducing wakefulness after sleep onset. The evidence suggests that alcohol’s effect on sleep efficiency is dose-dependent and is influenced by the specific sleep parameters being measured.

Alcohol’s Impact on Sleep Architecture

Sleep architecture refers to the distribution of different sleep stages, including NREM and REM sleep, throughout the night. Alcohol has significant, dose-dependent effects on sleep architecture, especially on the proportion of NREM and REM sleep.

1. N3 Sleep (Deep Sleep): Alcohol has a mixed effect on N3 sleep, the deepest stage of NREM sleep. At moderate doses, alcohol may initially increase the duration of N3 sleep, especially in the first half of the night. However, as alcohol is metabolized, there is a reduction in the amount of N3 sleep, and individuals tend to experience lighter sleep stages.
2. REM Sleep: Alcohol consistently disrupts REM sleep, an essential phase for memory consolidation, emotional regulation, and cognitive function. At lower doses, alcohol may delay the onset of REM sleep, while at higher doses, it reduces the total duration of REM sleep. The impact on REM sleep is most pronounced during the latter half of the sleep period, after alcohol has been metabolized and its sedative effects have diminished. This reduction in REM sleep is associated with cognitive deficits and mood disturbances.
3. Proportions of NREM Sleep: Alcohol tends to increase the proportion of NREM sleep, particularly N3, in the early stages of the sleep cycle. However, as alcohol is metabolized, the proportion of lighter NREM stages (N1 and N2) increases, indicating a shift toward less restorative sleep. This transition reflects the dose-dependent impact of alcohol on the sleep cycle, where the early sedative effects of alcohol promote deeper sleep, but later stages are marked by disrupted sleep patterns.
4. Dose-Dependent Effects: The impact of alcohol on sleep architecture is highly dose-dependent. Low doses of alcohol may facilitate sleep onset and initially promote deeper sleep. However, at higher doses, alcohol significantly disrupts REM sleep, impairs sleep continuity, and increases the likelihood of fragmented sleep in the second half of the night. The greater the dose, the more pronounced the negative effects on sleep quality, particularly regarding REM sleep.

Subjective Sleep Outcomes

Despite the objective evidence that alcohol disrupts sleep architecture, individuals often report improved subjective sleep quality following alcohol consumption. This discrepancy may be due to the initial sedative effects of alcohol, which can make individuals feel as though they are sleeping better. However, objective measures reveal that alcohol-induced sleep is often fragmented, with longer periods of wakefulness during the night. Therefore, while alcohol may reduce sleep onset latency, it is not associated with improved overall sleep quality or restorative sleep.

Sex Differences in Alcohol’s Effects on Sleep

Although the review did not provide conclusive evidence regarding sex differences in the effects of alcohol on sleep, physiological differences between males and females suggest potential variations in alcohol metabolism. For instance, women generally have lower levels of alcohol dehydrogenase, the enzyme responsible for alcohol metabolism, and lower total body water, which leads to higher blood alcohol concentrations for the same dose. These factors may contribute to different sleep outcomes between sexes, particularly in relation to alcohol’s sedative effects and its impact on sleep architecture. Moreover, hormonal fluctuations throughout the menstrual cycle or menopause could influence alcohol’s effects on sleep, although more research is needed to fully understand these differences.

Practical Considerations for Alcohol Use and Sleep

While alcohol may assist with sleep initiation, its long-term effects on sleep quality are detrimental. Chronic alcohol consumption is associated with a reduction in REM sleep and disturbances in sleep continuity, which can lead to cognitive impairments and emotional dysregulation. The evidence suggests that although alcohol may help some individuals fall asleep more quickly, it does not lead to better-quality sleep in the long run. Moreover, alcohol’s negative effects on sleep efficiency and architecture are dose-dependent, with higher doses leading to greater disruption in sleep.

Given the adverse effects of alcohol on sleep architecture and quality, individuals should carefully consider its use as a sleep aid. While occasional moderate alcohol consumption may not significantly disrupt sleep, habitual use or heavy drinking before bedtime is likely to impair sleep quality. It is important to explore healthier sleep strategies, such as cognitive-behavioral therapy for insomnia (CBT-I) or sleep hygiene interventions, as more effective long-term solutions for improving sleep.

Conclusion

This systematic review and meta-analysis highlight the complex, dose-dependent effects of alcohol on sleep. While alcohol may facilitate sleep onset and initially increase deep NREM sleep, it significantly disrupts REM sleep, impairs sleep continuity, and reduces sleep efficiency as the night progresses. These disruptions are particularly pronounced at higher doses of alcohol, which should be carefully considered for their potential impact on sleep quality. Given the negative effects of alcohol on sleep architecture, individuals seeking to improve sleep quality should be cautious about alcohol consumption, particularly close to bedtime.

Further research is needed to understand the underlying mechanisms behind alcohol’s effects on sleep and to investigate potential interactions between alcohol consumption, sex, and hormonal fluctuations. These findings emphasize the need for balanced approaches to alcohol consumption and sleep hygiene to support long-term sleep health.