What Science Really Says About Drinking Before Bed

Yes, there's a BAC limit for sleep.

03/10/2016 9:12 PM AEDT | Updated 04/10/2016 2:53 AM AEDT
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Alcohol is not doing any favors for your sleep. But how much boozing affects your sleep depends on when, how much and the time over which you drink.

There’s a lot of evidence that drinking before bed is doing you no favors in the sleep department. Most experts ― including the National Sleep Foundation ― put avoiding alcohol in the evening on the list of things to do to improve your slumber.

But as the temperatures start to fall and red wine season begins, is a little vino before bed really going to wreck our rest?

“Initially you might feel sleepy and fall asleep easily, but you end up awakening more often in the middle of the night and the alcohol has a disruptive effect on sleep,” Timothy Roehrs, director of research at the Sleep Disorders and Research Center of Detroit’s Henry Ford Hospital, told The Huffington Post.

Cabernet lovers everywhere, take note: That doesn’t mean one nightcap will guarantee a night of tossing and turning. “Usually it takes more than one drink to have any disruptive effects on sleep,” Roehrs said. 

Here’s everything you need to know about drinking before bed:

Why alcohol is so bad for your sleep

Alcohol knocks you out.

At first alcohol does make you drowsy, which should come as no surprise to anyone who has ever indulged in a glass of wine at the end of a long day.

Studies that compared brain activity in individuals after drinking with brain activity when the same people were sober show that our brains actually “turn off” quicker (and subsequently we fall asleep faster) after imbibing. The same sleep-inducing effect happens after drinking during the day, Roehrs said.

Unfortunately for our sleep, that’s not the end of the story.

As we move through our first cycle of sleep ― and sometimes the second cycle of sleep, depending on how many drinks we’ve had ― alcohol actually suppresses rapid eye movement sleep, Roehrs explained. REM is our lightest stage of sleep, when we dream and when a key part of the learning process happens that makes long-term memories “stick.” 

You’ll be tired and irritable the next day.

Instead during those first cycles of sleep, we fall (and stay) in the deepest and most restorative stage of sleep: slow wave sleep.

This sounds good, but research suggests after drinking, the quality of that deep sleep isn’t quite the same caliber our bodies tend to hit on nights we don’t imbibe ― and this lack of quality is linked to daytime drowsiness, headaches and irritability the next day.

You’ll wake up in the middle of the night.

What’s more, as our bodies metabolize the alcohol (i.e., as blood alcohol concentration returns to 0), our sleep experiences a rebound effect, Roehrs said. During that second half of the night, our bodies ― in an effort to make up for what was lost earlier in the night ― spend more time in REM sleep.

The effect of consolidating sleep in the first half of the night is offset by having more disrupted sleep in the second half of the night. Irshaad Ebrahim, medical director at The London Sleep Centre

The problem is REM sleep is when we are most likely to be awakened.

“The effect of consolidating sleep in the first half of the night is offset by having more disrupted sleep in the second half of the night,” Irshaad Ebrahim, medical director at The London Sleep Centre, previously said in a statement.

In a review of 153 studies that investigated the effect of alcohol on sleep, Ebrahim and his colleagues found alcohol consistently caused an increase in sleep disruption in the second half of a night’s sleep. 

One study that tracked brain activity in individuals after a night of drinking showed that they woke up roughly twice as often as they did after a night spent without drinking alcohol.

How to get smart about drinking before bed

How much and whether or not alcohol affects sleep depends on your blood alcohol content when you go to bed, Roehrs explained. His research has shown that a BAC equivalent to about 0.04 is the threshold at which sleep starts to be disrupted.

Step 1: Stop after the second round.

For an average 150-pound man, it would take about two drinks to raise a BAC to this sleep-disrupting level. And it would probably take closer to a drink and a half for a woman of the same weight to reach the same BAC.

Alcohol affects women differently than men, because women have fewer of the gut enzymes that metabolize alcohol than men do. And pound-for-pound, women have less water in their bodies than men do. That means more of the alcohol women drink goes directly into the blood compared with how the same quantity of alcohol would affect men, because in a man more of the alcohol ends up in body water.

Step 2: End with a snack

Here’s one easy thing you can do to lessen the effect alcohol has on your BAC (and therefor your sleep): Eat something. Food delays how quickly you absorb alcohol, which can help lower your BAC.

Step 3: Consider happy hour

Timing matters. Adults typically metabolize alcohol at a rate that decreases BAC by about 0.01 to 0.02 per hour. And, in theory, if you drink earlier enough in the evening ― happy hour, anyone? ― your BAC has time to drop below the 0.04 threshold before bed.

That means if your BAC is 0.08, it could take as long as four hours once you stop drinking for it to return to 0.04 ― though this depends on things like gender and weight, too.

The bottom line: Alcohol will disrupt sleep, but drinking in moderate amounts and long enough before bedtime can still let you snooze easy.

Sarah DiGiulio is The Huffington Post’s sleep reporter. You can contact her at   

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