Should You Nix the Nightcap? How Alcohol Impacts the Sleep Cycle

Alcohol and sleep have a complicated relationship. Booze has long been considered a sleep aid, hence the term nightcap. But the impact of a nightcap on your sleep cycle is actually quite complex. Let’s take a closer look.

First, alcohol acts like a stimulant, filling the brain with endorphins that make you more social, self confident, and generally happier. Shortly after, booze acts like a sedative, especially if you stop drinking. That’s where the term nightcap comes into the picture.

A 2013 review of 27 published studies found that alcohol reduces the time it takes to fall asleep and increases the amount of deep sleep during the first two hours of the sleep cycle. This is because alcohol is a fast acting drug that goes straight to your bloodstream. But shortly thereafter, the liver metabolizes the alcohol and your blood alcohol level goes back down to normal. Once your BAC goes down, you start to wake up. This is called the rebound effect, which means that you’ll be wide awake by 4 am.

Research published in Alcoholism: Clinical and Experimental Research shows that drinking reduces rapid eye movement sleep. This is the deepest stage of sleep when most dreams and learning occur and where memories are likely stored.

“This review confirms that the immediate and short-term impact of alcohol is to reduce the time it takes to fall asleep,” lead author of the study Irshaad Ebrahim, director of the London Sleep Center, said in a statement. “In addition, the higher the dose, the greater the impact on increasing deep sleep.”

According to the study, the amount matters. If you have 1-2 drinks it increases slow wave sleep while not impacting REM sleep. While a night of heavy drinking can cause seriously disturbed sleep because your REM sleep is impacted.

“SWS or deep sleep generally promotes rest and restoration,” Ebrahim said in Time, cautioning, however, that alcohol increases in this stage can worsen sleep apnea and sleepwalking in people who are prone to those problems.

Alcohol and Prescription Sleep Aids

Combining booze with prescription sleeping pills is a recipe for disaster. It can cause accidents, overdoses, and liver damage, according to a study at Santa Clara University:

The combination can lead to extreme depression of the Central Nervous System and can be fatal. When combined with alcohol these drugs have a synergistic effect, meaning that the combined depression of the CNS is greater than the sum of the depression caused by alcohol and that of the sedative. This effect can be expressed with the equation 1+1=3 (the combined effect is more intense than the separate effects combined).

Combining alcohol and sleep is also disruptive to your partner because it increases snoring, night sweats, and nightmares. Ever been awakened by your flailing partner snoring like a train after a big night out? You’re not alone. Research at the University of Wisconsin-Madison shows that men especially suffer longer episodes of disordered breathing and snoring when they mix alcohol and sleep.

The long and the short of it: if you want to sleep and you want to enjoy a glass or two of wine, finish drinking at least 3 hours before bedtime, control your amounts, and hydrate. In other words, nix the nightcap.

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