Dave Gibson
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Food Science of Sleep

How does alcohol effect sleep

Most of us would agree with the statement that alcohol helps you fall to sleep more easily. However, sleep scientists have now shown that the impact of alcohol on the quality of sleep makes its use as a sleep aid one to avoid. As Mathew Walker describes in his brilliant book Alcohol ‘sedates’ you, rather than gets you to sleep.

Here is a background to Alcohol’s effects on sleep, and why the overall advice for those who drink too much before bedtime is that if you ‘booze you lose’

A quick acting sedative, but then the disruption starts

Without a doubt it’s easier to get to sleep when we drink. Alcohol allows reduces ‘sleep latency’ which is the amount of time it takes to get to sleep. Once asleep, alcohol then increases the proportion of deep sleep during the first part of the night. Theoretically this increase in deep sleep is positive, as deep sleep is associated with the body’s healing process via the secretion of growth hormone. However, studies have shown that alcohol induced sleep sees an overall decrease in growth hormone produced despite the fact that there has been an increase in deep sleep. It’s also been shown that the more you drink the greater the reduction in growth hormone secretion.

You won’t remember

Drinking too much alcohol before bed also reduces the amount of Rapid Eye Movement (REM) sleep, which is the part of sleep where we dream and form memories. As the body starts to metabolise through the night alcohol its break down produces chemicals including aldehydes.  These aldehydes then build up and up and eventually block the brain’s ability to generate REM sleep. As we get naturally get more REM sleep in the second half of our night than the first, drinking alcohol in the evening can have a massive effect on this vital period of our sleep.

For moderate and heavy drinkers, the impact of disruption in REM sleep is felt the next day with poor concentration, poor memory and sometimes daytime sleepiness. The more you drink before bed, the more pronounced these effects. What’s somewhat surprising even if we drink three nights after learning something new our ability to recall the detail is still reduced. It would seem that memories are consolidated over consecutive rather than a single night’s REM sleep.

For those who are light drinkers (less than two drinks) researchers have concluded that this level of alcohol consumption is not shown to have this effect on REM Sleep.

Further disrupted sleep

Drinking alcohol gives us a burst of adenosine, a chemical produced in the brain during the day which helps us get to sleep at night. This quick burst works as a sleeping aid, however the kick back later is thought to be part of the process which leads to disrupted sleep throughout the night. These disruptions more often than not go undetected, and are only noticed with the resulting sluggishness the morning after.

Another factor is that alcohol use suppresses the sympathetic (fight or flight) nervous system. Whilst this suppression helps us get to sleep as the blood level of alcohol drops later in the night, the sympathetic nervous system then becomes re-activated and wakes us. This part of the nervous system is also responsible for the night sweats and headaches that people can suffer with over-drinking.

Additionally, as alcohol is a diuretic it is likely to make you need to go to the bathroom more often in the night, leading to further broken sleep.

For those with sleep disorders

As alcohol suppresses breathing it can exacerbate sleep apnoea, a condition which occurs through the night in suffers, with pausing in breathing.  Furthermore, alcohol can also reduce the brain’s ability to wake and detect a lack of oxygen in the body, and this can lead to longer and more frequent breathing pauses. As such, it is recommended that people with sleep apnea either avoid drinking alcohol altogether or at least cut back on their drinking.

Alcohols effects on increasing snoring are also well documented. Alcohol consumption allows all the muscles of the body to relax, including your throat muscles which then leads to the vibration of snoring.

Booze you lose

Moderation is therefore the key to a good night’s sleep for all. For those however who who drink too much before bedtime the message is that ‘if you booze you lose’