Why does alcohol disrupt my sleep?

The relationship between alcohol and sleep patterns

Have you ever noticed that when you drink alcohol before bed, you typically fall asleep faster, but then wake up through the night or toss and turn? This is because drinking has been shown to directly affect your quality of sleep. Alcohol in your system disrupts your Rapid Eye Movement (REM) stage of sleep — even if it’s just a couple of drinks.

How sleep cycles work

Sleep cycles consist of 4 stages: 3 non-rapid eye movement (NREM) stages, and one rapid eye movement (REM) stage. During the NREM stages (collectively stages 1-3), a person falls asleep, moving from light to deep sleep. The muscles are relaxed, temperature is dropped, and slowed breathing & heart rate all contribute to this stage of deeper sleep.  Simultaneously, brain waves show a new pattern, and eye movement stops. REM sleep occurs about an hour after you fall asleep, and this is when you tend to have vivid dreams. Every REM stage that follows gets longer (the first REM period lasts 10 minutes, and they get longer from there). Your buddy experiences faster breathing and increased heart rate & blood pressure. 

How alcohol moves through your system

GABAa receptors are the inhibitory neurotransmitters that are affected by alcohol. They assist in focusing, help control fear and anxiety, and suppress distractions. When you drink, the GABAa receptors increase their effects, causing you to feel more relaxed. These effects also help you fall asleep faster. Additionally, alcohol supresses REM sleep, which is when the deepest sleep occurs. This contributes to great sleep during the first half of the night, when your blood alcohol concentration (BAC) is still in your system. 

Once your BAC levels start to drop, it has the opposite effect on your sleep. Your brain goes into rebound, causing you to toss and turn. By the time your blood alcohol concentration hits zero, you're in full blown withdrawal, leading to severely disrupted sleep, and in turn, magnifying your hangover.

Drinking & snoring

Another side effect of drinking pre-bedtime results in more (and louder) snoring. Alcohol relaxes your muscles and narrows your respiratory pathways, disrupting your normal breathing and causing sleep apnea & snoring.

Start early, end early.

A nightcap is not the way to go. You can manage your sleep patterns better by giving your body enough time to metabolize alcohol before falling asleep. If you plan on drinking, ideally try to have a few hours of buffer before bedtime. The earlier you stop drinking, the more time your body has to go through GABAa rebound. This will ensure you having a more restful sleep and happier morning.