Do you have a drink or two in the evening as a way to relax and help you to fall asleep? If so, you’ve got plenty of company. Alcohol is among the most common “sleep aids” that people employ to help them drift off at night. We know that alcohol doesn’t solve problems for sleep: it creates them. And a new study suggests yet another reason that alcohol can be a roadblock to good sleep: the stimulating effects of alcohol are felt more strongly in the early evening hours. That evening drink you think is sending you toward slumber? It’s likely doing just the opposite.
The effects of alcohol in the body are what are known as biphasic, meaning “in two phases.” When first consumed, alcohol has a stimulating effect. Later, after alcohol has been in the system for a period time, its effects are sedating. But as this new research indicates, the effects of alcohol—particularly the stimulating effects—are magnified during certain periods of the body’s 24-hour circadian cycle.
Many people are drawn to alcohol for both its stimulating effects and its sedating ones. Often people drink in the evenings to help them unwind and fall asleep at night. It may feel as though a drink or two in the evening can help to relax and pave the way for a good night’s sleep. But it’s actually not the case. Alcohol consumption, in excess or too close to bedtime, diminishes the quality of sleep, often leads to more waking throughout the night, and lessens time spent in REM sleep and slow wave sleep in the later part of the night, the deepest and most restorative phase of sleep.
This latest study sheds some interesting and important light on how the timing of alcohol consumption may influence how strongly its biphasic effects are experienced. Researchers at Brown University investigated how the effects of moderate alcohol consumption might vary depending on the phases of the body’s circadian clock, and the timing of drinking. They found that the timing of drinking appeared to make a difference in the effects of alcohol. In their results, drinking in the evening and before bedtime is associated with significant stimulating effects, compared to other times of day.
Researchers conducted a study using 27 men and women between the ages of 21-26.
While in the laboratory, researchers were able to isolate and analyze the effects of alcohol during several distinct periods within each participant’s circadian cycle. At four times throughout the day and night, participants were given a drink, either a mixed alcoholic drink or a placebo that mimicked the taste of the alcoholic drink.
Researchers took several measurements throughout each day and night, including:
- Breath alcohol concentration, to measure amount of alcohol in the bloodstream.
- Sleep latency onset, to measure the amount of time it took to reach the first stages of sleep, from the beginning of a sleep period. The shorter a sleep latency onset measurement, the faster a person has fallen asleep. This is a standard, objective measurement of sleepiness
- Biphasic alcohol effects, to measure the degree and timing of stimulation and sedation as perceived by each individual. This is a subjective measurement of the effects of alcohol as both a stimulant and a sedative.
- Confirm the biphasic nature of alcohol as it is processed in the body. People who drank took longer to fall asleep as their blood alcohol content rose. They also reported feeling more stimulated, compared to people who drank the placebo. As blood alcohol content fell, those people felt sleepier and fell asleep more quickly than those who drank the non-alcoholic placebo beverage.
- Indicate that the timing of drinking, relative to the body’s circadian clock, matters in how alcohol affects sleepiness and sleep onset. During the late day and early evening circadian phase (Happy Hour), people who drank alcohol experienced longer sleep latency onset compared to other points in the circadian cycle. The same was true for the subjective, self-reported measurement of stimulation and sedation: the ratings of stimulation were not only higher among people who drank than those who didn’t, but they also were highest during the late-afternoon/early-evening circadian period.
We’ve seen other research that shows the influence of time of day on the impact of alcohol as a stimulant and a sedative. We’ve also seen research that indicates circadian timing plays a role in alcohol’s effects on sleep. This latest study is the first to pinpoint the varying effects of alcohol in specific circadian phases, and to isolate the significant stimulating effects of alcohol consumed in the late day and early evening. This, of course, is precisely the time when people are most likely to drink (think: happy hour) and also most likely to use alcohol as a sedative toward sleep.
These results are an important step forward in understanding the effects of alcohol in the body. They provide another compelling piece of evidence that alcohol’s role as an “aid” to sleep is misguided. I’m not suggesting that people shouldn’t drink in moderation. But we all need to be aware of the effects alcohol has on our ability to sleep well.
Michael J. Breus, PhD
The Sleep Doctor™