Researchers have been studying how alcohol affects sleep for nearly a century. Because alcohol acts as a depressant on the central nervous system, its sedative effect can help you relax and fall asleep faster. But once alcohol metabolizes in the body, it disrupts your sleep and interferes with the vital processes during the deep sleep cycle. For the nearly 30 million Americans who suffer from sleep apnea, alcohol can worsen the severity of this sleep health disorder.

The Stages of Sleep

To better understand how alcohol interferes with sleep, it is helpful to know how your body transitions from wakefulness to sleep. When you sleep, your body cycles through four stages divided between non-REM (Rapid Eye Movement) or quiet sleep and REM sleep, also known as active sleep.

During the first three stages, breathing and heart rate slow as the body begins to fall asleep. The last of the non-REM stages, known as deep sleep, is when a host of important biological processes take place. This deep sleep phase is responsible for cell regeneration, tissue repair and growth, and the strengthening of the immune system. 

The last sleep stage, known as REM, is when your breathing, heart rate, and blood pressure increase; as the name indicates, the eyes begin moving. REM sleep occurs about 90 minutes after you fall asleep and is when we do our most vivid dreaming. Unlike deep sleep, REM sleep is associated with brain function rather than the body’s biological processes.

According to the Sleep Foundation, these four cycles repeat throughout the night resulting in four or five cycles per eight hours of sleep. Because of alcohol’s sedative effect, you may fall into a deep sleep quickly, but this leaves an imbalance in the sleep cycles. As a result, less time will be spent in the deep sleep phase and more time in the active REM phase. This reduction leaves you feeling less rested, groggy and can affect mood, memory, and overall cognitive function.

Alcohol and Obstructive Sleep Apnea

A person diagnosed with obstructive sleep apnea (OSA), the most common form of sleep apnea, also wakes up feeling tired and experiences daytime grogginess and brain fog. During a sleep apnea event, the muscles in the throat and mouth relax, creating a blocked airway, resulting in multiple arousals from sleep throughout the night. This sleep-wake pattern is most recognizable by the snoring and grunts that occur when struggling for breath.

Researchers believe that alcohol can exacerbate sleep apnea because the sedative effect of alcohol also relaxes the muscles in the throat, mouth, and nose, adding to the already obstructed airway. While it is debated whether or not alcohol can actually cause sleep apnea, there is much anecdotal evidence to suggest further study.

Suppression of hormones

Alcohol also suppresses the production of hormones in the body that help regulate sleep, including melatonin. Melatonin is often referred to as the sleep hormone, as it increases when it gets dark outside, signaling that it is time for sleep. It plays an essential role as a regulator of our circadian rhythm, also known as our biological clock. The National Institute of Health’s Heart, Lung and Blood Institute defines circadian rhythm as the natural cycle of processes our body goes through in a 24-hour period.

Our circadian rhythm controls the sleep-wake cycle in addition to other physical, mental, and behavioral processes and is mainly affected by light and darkness. Even though alcohol can make you feel tired and help you get to sleep, once in your system, it will suppress the amount of melatonin produced in the brain, resulting in disrupted sleep cycles and less restful sleep. This can lead to a dangerous habit of drinking to fall asleep because you have had a poor quality night of sleep, leading to alcohol abuse. 

In Summary

The poor quality, disrupted sleep associated with obstructive sleep apnea can lead to more serious comorbidities, including cardiovascular disease, high blood pressure, and even diabetes. Because alcohol can worsen sleep apnea, sufferers should drink in moderation and stop alcohol consumption at least a couple of hours before going to sleep. If CPAP is the recommended sleep apnea treatment, it is best to continue use and not allow alcohol to get in the way of getting a restful night of sleep.