The Science Behind How Alcohol Kills Your Sleep

Few people are strangers to the nightcap — a glass of wine, two fingers of whiskey, or maybe even a White Russian to wind things down before climbing into bed for the evening. No doubt, just one drink after a long day can help a person relax when it’s most needed and that’s exactly why the nightcap is so common. Once the initial buzz wears off, flooding the brain with endorphins to make you feel good, alcohol starts to work as a sedative. You feel drowsy and before you know it, it’s time to get some sleep.


Mission accomplished, right?

The truth is, drinks before bed are actually far more damaging to the quality of sleep you’re going to get than they are helpful. Nowadays, there’s plenty of science to back the suggestion that you should actually avoid that nightcap altogether for the sake of a good night’s sleep tonight as well as saving yourself from some long-term sacrifices to your health.


First, research does support that alcohol reduces the amount of time it takes you to fall asleep and increases the amount of deep sleep you’ll get initially. Both these are positives on the surface but once those effects wear off, you’re actually facing a massive increase in sleep disturbances in the second half of the night.


Take the concept of “sleep architecture,” for example, which organizes the order and variation of different stages of sleep: Rapid Eye Movement and Non-Rapid Eye Movement. There are typically four different stages of NREM followed by a brief period of REM, a process that repeats itself multiple times throughout the night as each REM period gets longer and longer throughout the night. With alcohol, however, alcohol decreases REM sleep overall, even delaying the first period of REM.


Now, a night of heavy drinking will throw all of this off entirely. As the liver metabolizes the alcohol, your sleepiness starts to wear off to the point that you’ll likely find yourself wide awake by 4 am. And even if you do manage to get back to sleep before the sun comes back up, don’t expect to get back to into a deep sleep again, as you’ll be uncomfortably tossing and turning, sweating as a result of the vasodilation caused by alcohol. This is a process in which your blood vessels widen, warming the skin and calling your sweat glands into action. It will effectively cool you down but it will also raise the odds of even more sleep disturbances.


And as if you didn’t have enough reasons to spend the night not sleeping now, expect to have to get out of bed altogether as well because you’ll probably be running to the bathroom. Alcohol suppresses the anti-diuretic hormone, vasopressin, interfering with the amount of water your kidneys absorb. Alcohol is such a strong diuretic that one study discovered every 1g of alcohol you consume, urine excretion goes up by 10ml.


So with all that said, skip the nightcap and whenever possible, give your binge drinking nights a cutoff time, allowing yourself as much time as possible to metabolize that alcohol before you try to fall asleep. Who knows, it might save you a sleepless night or two.

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