Drinking alcohol right before bed can certainly make you drowsy—but will result in a night of poor sleep overall, according to new research from Australia's University of Melbourne.
"Alcohol is not actually a particularly good sleep aid," Dr. Christian Nicholas, a research fellow at the university's Sleep Research Laboratory, told Wine Spectator. "Even though it may seem like it helps you get to sleep quicker, the quality of the sleep you get is significantly altered and disrupted."
For their recent study, published in Alcoholism: Clinical and Experimental Research, Nicholas and co-author Dr. Julia Chan studied the sleep patterns of 24 college students—12 men and 12 women—ages 18 to 21, on three separate nights. (The legal drinking age Down Under is 18.)
All subjects received both alcoholic drinks (orange juice with vodka) and placebo drinks (orange juice with a vodka-dipped straw) over the course of the experiment; alcohol content was adjusted for body weight, designed to produce a peak blood-alcohol content (BAC) of 0.1 percent. Subjects' sleep patterns were observed overnight by electroencephalogram (EEG), which monitors electrical impulses in the brain.
Understanding sleep remains a relatively new scientific endeavor, and research that employs an EEG is newer still. Previous studies focused on the effects of alcohol and sleep have been inconclusive. Nicholas' and Chan’s research builds upon these previous findings with a more-comprehensive exploration of the effects of acute alcohol consumption across different sleep cycles and in different brain regions.
As anyone who’s gone to bed after several drinks will tell you, alcohol initially put the subjects right to sleep, and they slept deeply for the first half of the night. But the second half of the night proved to be restless. "We showed that after pre-sleep alcohol consumption there is an increase in slow-wave sleep early in the night, and later in the night there is a lot of sleep disruption, greater numbers of awakenings and more time spent awake," said Nicholas.
Slow-wave sleep is marked by high delta activity (delta waves are the brain waves associated with the deepest level of sleep). In the second half of the night, those who had consumed alcohol experienced what's known as alpha-delta sleep—which means that alpha waves (those associated with a state of calm wakefulness, such as would be achieved in meditation) and delta waves were occurring at the same time."The simultaneous increase in alpha power observed after alcohol, we believe, indicates that NREM sleep [non-rapid eye-movement sleep, or dreamless sleep] is being disrupted, and thus the normal restorative effects of sleep are likely not being achieved," said Nicholas.
The reasons why alcohol affects sleep were not directly addressed here, but one hypothesized mechanism has to do with a major inhibitory neurotransmitter called GABA, which helps to regulate sleep. Nicholas explained that alcohol can mimic or stimulate GABA activity, thus interfering with its regulation.
Nicholas and Chan chose college students as their sample group because sleep patterns tend to change significantly during late adolescence—and so do alcohol-consumption habits. Adolescents show a sharp decline in slow-wave sleep and delta activity frequency beginning at the age of 12 and stretching sometimes into their twenties. Although acute alcohol consumption might not change sleeping patterns permanently, Nicholas noted, “it is highly likely that chronic drinking does have effects on sleeping patterns, though it is unclear exactly why the changes appear.”
So how should one proceed when it comes to wine before bedtime? "The National Institute on Alcohol Abuse and Alcoholism [NIAAA, part of America's National Institutes of Health] considers moderate drinking as up to one drink per day for women and up to two drinks per day for men," said Nicholas. "Drinking at these levels is unlikely to significantly disrupt your sleep. So if you are drinking, ideally BAC should be minimized by the time you go to bed (meaning drinking in moderation and stopping preferably several hours before bedtime), and ensuring that you have adequate time in bed to get a good night’s sleep."