Alcohol Affects Sleep Patterns 

Do you like to have a beer or a glass of wine with dinner?
Do you regularly drink alcohol?

A small amount of alcohol can’t have much of an impact on sleep can it?

Or can it?

It's already well established in sleep medicine that drinking impacts sleep cycles and makes sleep disorders such as insomnia, obstructive sleep apnea, and restless legs syndrome worse. 

People mostly tend to notice the sedating effects of alcohol. In terms of sleep cycles, this typically shows up as faster times to get to sleep or “shorter sleep onset” times as a researcher might say. 

But the effects of alcohol on sleep don't stop there.

You’ll also hear sleep scientists say that alcohol increases slow wave sleep (SWS) or deep sleep at the start of the night and decreases the amount of REM sleep in the first half of the night. 

But hold on.

Deep sleep is the kind of sleep that gives us physical repair and restoration. So getting more of that is going to be a good thing right? Wouldn't that mean the quality of your sleep would be better?

Not so fast.

Sleep After Drinking Isn't The Same

A study by researchers from the Sleep Research Laboratory at The University of Melbourne has uncovered some lesser known ways drinking can affect your sleep that may require you to think again.

The team sourced 24 participants (12 males, 12 females) between the ages of 18-21 for a study on social drinking habits. All participants had consumed less than seven standard drinks in the past 30 days

The study utilized a double-blind procedure, where each participant was given pre-sleep alcohol or placebo followed by polysomnography recordings to measure EEG activity.

Like many studies the results found that alcohol consumption led to increases in SWS delta power in individuals during NREM (non-REM) sleep - that’s an increase in deep sleep. 

So far so good. 

But the scientists also noted something else:

Effects Of Alcohol On Sleep

Brain scans revealed participants also showed concurrent increases in frontal alpha power, or alpha waves in the frontal parts of the brain. Alpha brain waves are actually a phenomenon associated with disturbed sleep or light sleep.

Lead author of the study, Christian L. Nicholas explained that these increases in frontal alpha power caused by pre-sleep alcohol consumption indicates a disruption of the usual characteristics of Non-Rapid Eye Movement (NREM) Slow Wave Sleep. 

He noted that similar increases in alpha-delta activity are associated with unsatisfactory or non- restorative sleep and impaired daytime performance. 

In fact these are the kind of brain wave patterns that have been observed in the sleep of people suffering from chronic pain. 

This led to the researchers suggesting that if sleep is frequently disrupted due to pre-sleep alcohol use over extended periods of time, chronic alcohol consumption, it could have a considerable negative impact on the wellbeing of drinkers during the day and cognitive functions such as learning and memory.

Nicholas stated:

"Although the exact function of (NREM) non- Rapid Eye Movement  sleep, and in particular SWS, is a topic of debate, it is thought to reflect sleep need and quality; thus any disruption to this may affect the underlying restorative properties of sleep and be detrimental to daytime functioning."

This means that sleep researchers need to be alert to simply assuming the deep sleep or SWS seen with consuming alcohol is the same as in non-drinkers

Nicholas said:

"For individuals researching sleep in the field of alcohol studies our findings indicate that care needs to be taken when interpreting increases in 'visually scored' SWS associated with alcohol consumption. 

Increases in SWS, which traditionally would be interpreted as a good thing, can be associated with more subtle changes indicating disrupted sleep, such as the increases we observed in alpha activity, which are revealed when more detailed micro-structural components of the sleep electroencephalogram are assessed."

And for the public there needs to be more awareness of the health impacts of drinking in the evening and the negative effect on sleep quality. Although alcohol may make you fall asleep quickly, the quality of sleep you get has been considerably altered from that of a natural sleep cycle. This is likely to be especially true for those that regularly drink with their evening meal. Moderate alcohol consumption (e.g. one drink a night), could lead to consistently non-refreshing sleep and increasing levels of fatigue. 

The study was published in the journal Alcohol: Clinical and Experimental Research (Chan et al., 2015).

Clinical Comment

In working with sleep disorders and sleep issues we are looking at client sleep logs/diaries every day. From this experience we've noticed the impact of regular alcohol consumption on sleep quality is under-appreciated by the public. 

It’s not hard to spot on a sleep log that those that use alcohol have sleep problems in the form of increases in the number of awakenings, and increases the length of those awakenings. Fragmented sleep is standard with alcohol. But the more subtle effect from alcohol intake is that regular drinkers have increased levels of daytime fatigue owing to the poorer sleep quality that results from not getting the deep type of sleep the body needs to feel refreshed. 

Often we see a spontaneous increase in people feeling rested and refreshed by their night's sleep once they eliminate alcohol from evenings. This can happen without any appreciable improvement in sleep quantity or wake ups etc. This research sheds light on the hidden ways alcohol may be affecting your sleep and what might be behind our clinical observations.

As always, if you think you need support, or you have questions about treatment then get in touch or book an appointment directly.

And don’t forget that, while we primarily see individuals suffering from insomnia, alcohol can also worsen other sleep disorders such as obstructive sleep apnea and restless legs syndrome.  

Article Author: Dan Ford Sleep Psychologist