How Bad Is It Really to Drink Alcohol Before Bed?

When's the last time you were buzzed when you hit the sack? Maybe you had a cocktail (or two) after dinner, or winding down with a chilled glass of chardonnay is part of your nightly routine.

Well, that evening cocktail hour can backfire. Ironically, even though drinking can make you feel drowsy, experts agree that it's kryptonite to a good night's rest.

"Alcohol can make you quickly become unconscious, but it will not help you achieve normal, healthy sleep," says neurologist and sleep specialist Chris Winter, MD, author of ‌The Sleep Solution‌. "In fact, it suppresses many of sleep's positive, restorative aspects."

Here, we explore how a nightcap affects your body and brain, and whether it throws your sleep just slightly off track — or majorly out of whack.

Initially, booze has a sedative effect. "Acute alcohol intake induces the release of adenosine, a substance naturally produced by the body to promote sleep," says Anita Shelgikar, MD, associate professor of neurology and director of the sleep medicine fellowship at the University of Michigan. As a result, you're more likely to crash as soon as your head hits the pillow.

Drinking also suppresses anxiety. If you tend to have trouble switching off your racing mind at night, alcohol helps you chill out. "It is an anxiolytic, so it makes you relax," Dr. Winter says.

Sounds good, right? But drinking your way to dreamland can have hazardous consequences.

"When alcohol tolerance develops, the individual needs more alcohol in order to achieve the same sleep-promoting effects," Dr. Shelgikar says.

People become tolerant to booze's sedative qualities in as little as three days, according to the National Institute on Alcohol Abuse and Alcoholism (NIAAA). Not to mention that upping your intake can set off a host of other problems — including potentially setting you on a slippery slope to alcohol use disorder.

Throughout the course of a typical night, your brain cycles among light sleep, slow-wave sleep and rapid eye movement sleep (or REM, the sleep stage when dreaming takes place). But drinking alters this architecture.

"In the first half of the night, alcohol increases the amount of time you spend in slow-wave sleep," Dr. Shelgikar says.

Slow-wave sleep is the deepest stage of sleep, which sounds like a good thing to get more of. This type of sleep plays a vital role in repairing tissue, consolidating memories, building bones and muscles and fortifying the immune system, according to a January 2013 review in ‌Alcoholism, Clinical and Experimental Research‌.

Slow-wave sleep is also when your body churns out growth hormones. "Growth hormones are critical for bone strength, immune function and injury recovery," Dr. Winter says.

Now here's the bad news: Booze can interfere with these benefits. Consuming alcohol before bedtime results in the suppression of growth hormones despite the uptick in slow-wave sleep, according to the NIAAA.

"Furthermore, alcohol dramatically decreases REM sleep in the first half of the night and potentially the entire night," Dr. Shelgikar says. "REM sleep is related to cognitive ability, including memory, learning and concentration. Disrupting REM can be problematic in optimizing health and performance."

After initially lulling you into a few hours of deep sleep, alcohol then triggers a series of disruptions throughout the second half of the night.

"It takes about three hours to metabolize alcohol," Dr. Shelgikar says. At that point, you'll probably find yourself making bathroom runs in the middle of the night, since booze suppresses vasopressin, an antidiuretic hormone.

What's more, booze might interfere with breathing. Drinking is associated with a 25 percent greater risk of obstructive sleep apnea (when tissues in your throat block your airway during sleep), perhaps because it increases the collapsibility of the upper airway and contributes to a higher BMI, per a February 2018 review in ‌Sleep Medicine.‌

"Studies have also shown that alcohol use leads to longer durations of apneas, along with a more dramatic drop in oxygen levels," Dr. Shelgikar says.

On top of all that, the dehydrating effects of a nightcap lead to more snoring and lighter sleep, per the National Sleep Foundation.

Fragmented sleep means you might be off your game the next day. "You're more likely to be tired and disoriented and have difficulties concentrating," Dr. Winter says.

And keep in mind that alcohol-fueled nocturnal awakenings chip away at your total amount of shut-eye. So even if you're in bed for 7 or more hours, as recommended by the American Association of Sleep Medicine, you're actually logging fewer zzzs.

"Disruptions to the overall quantity and quality of your sleep can have a negative impact on your cardiovascular health, cognitive function and metabolic outcomes," Dr. Shelgikar says.

Luckily, even if you do tip one back before bed, there are measures you can take to minimize the damage.

Give yourself a cutoff of at least three hours prior to hitting the hay (longer if you drink more). According to the NIAAA, that's approximately how long it takes an adult to metabolize one drink on an empty stomach.

That goes up to 4.5 hours to process two drinks, 6 hours for three beverages and 7 hours if you've had four servings.

"You want to give yourself a buffer in which your body can metabolize the alcohol prior to bedtime," Dr. Shelgikar says.

Eating a meal including fat, protein or carbs may reduce the total amount of alcohol absorbed into your body and helps you metabolize it more quickly, per a November 2013 ‌Clinical Liver Disease‌ review‌.‌

"Just be mindful of your overall intake," Dr. Shelgikar says. "Sometimes when there is less alcohol absorption you end up drinking more."

Although even a single cocktail affects sleep quality, the less you knock back, the better.

"I've never met someone who stopped drinking heavily and didn't notice a positive change when it came to their sleep quality and the way that they felt the next day."

Low alcohol intake (less than 0.25 grams per kilo of body weight) reduced physiological recovery during sleep by about 9 percent on average, per a January 2018 study in ‌JMIR Mental Health.‌ That went up to 24 percent with moderate consumption (between 0.25-0.75 g/kg) and 39 percent after heavy drinking (greater than 0.75 g/kg).

Bottom line: The more you drink, the less your body bounces back from the effects of alcohol as you sleep.

It depends on the amount you sip and what time you do it.

"If you have a glass of wine with dinner at 8 and then go to bed at 11, it's not a big deal," Dr. Winter says. "But consuming an entire bottle of wine every night, beginning when you're cooking and finishing it after the meal, is a big deal."

Dr. Winter references what he calls the "cupcake analogy:" If coworkers bring in cupcakes once in a while to celebrate a birthday, go for it. But indulging in sweets on the reg isn't great for you.

"Similarly, if you tear it up once a year, it's probably irrelevant, but understand that [you've] missed out on your [restorative sleep] that night," he says. "On the other hand, if you're drinking at night 30 percent of the time, then you are making the decision to turn your back on the normal synthesis and release of growth hormones."

If you're unsure where your drinking falls, experiment by quitting for two weeks. "I've never met someone who stopped drinking heavily and didn't notice a positive change when it came to their sleep quality and the way that they felt the next day," Dr. Winter says.