If you’re a young woman wondering why you feel sleepier than your boyfriend after a night on the town, it may not be all in your head. According to a recent study, women’s sleep is more disrupted than men’s after an evening of alcohol intoxication.
Numerous studies have demonstrated that alcohol influences our perception of how well we’ve slept the night before. Objective measurements such as how quickly it takes to fall asleep, length of deep sleep and total sleep, number of wake-ups during the evening and how quickly it takes to fall back to sleep confirm this perception.
To determine if subjective and objective measures of sleepiness differ between men and women after alcohol intoxication, researchers recruited 93 healthy, college-aged students (median age 24 years). Drinking behaviors and family history of alcoholism were recorded with over 91 percent consuming alcohol at least once a week. When out drinking, the students had 3 drinks on average.
Students visited a sleep lab on two occasions (separated by about 1 week), with each visit lasting 2 evenings. Participants were randomized to receive either alcoholic drinks (Wild Turkey or Absolut Vodka mixed with caffeine free Coke) on one visit and a placebo on the other visit (caffeine free Coke with a few drops of alcohol floated on surface).
Upon arrival at the sleep lab in the late afternoon, students were given a meal. Then, between 8:30P and 10:00P, they were given either placebo or alcoholic drinks. Those receiving alcoholic drinks were closely monitored and alcohol content was adjusted based on gender and weight. After three drinks, each alcohol participant had to reach a Breath Alcohol Content (BrAC) target of 0.11% (visibly drunk; comparable to 0.08% blood alcohol concentration which is the legal limit in the U.S. †).
“Following alcohol, women’s total sleep time was reduced by almost 20 minutes and they experienced a 15 minute increase lying awake relative to placebo.”
Once the targeted BrAC was reached, participants were instructed to sleep between the hours of 11:00P to 7:00A. During the evening, brain activity was recorded along breathing and body movements. Upon awakening, the students received breakfast and completed a battery of tests for 90 minutes.
Using a sleepiness scale, students consuming alcohol reported feeling more sleepy at bedtime and in the morning when compared to those who drank a placebo. But, the effects of alcohol were magnified in women where they felt sleepier at bedtime than men.
Objective data collected including brain wave patterns and eye movement confirmed that sleep patterns were influenced by alcohol intake. Alcohol reduced how long it took to fall asleep (sleep latency) by about 4 minutes, how well the students slept and increased by almost 10 minutes how awake a person was during the night. The alcohol induced students also spent more time in lighter sleep and took longer to attain the stage of deep sleep or Rapid Eye Movement (REM) sleep.
Differences were also observed by gender. In general, alcohol disrupted sleep more in women than in men. Following alcohol, women’s total sleep time was reduced by almost 20 minutes and they experienced a 15 minute increase lying awake relative to placebo. Among women, the number of nighttime awakenings also increased and sleep efficiency (the total amount of time sleeping vs time in bed) decreased by nearly 4 percent during the evening. In comparison, sleep continuity following alcohol was equivalent to placebo in men.
Study authors hypothesized that the greater sleep disruptions in women may be related to the sex differences in how alcohol is metabolized. At equivalent peak breath alcohol concentrations, BrAC declines more rapidly in women. Higher concentrations of alcohol have a sedative effect whereas lower levels have a stimulant affect. If alcohol wears off more quickly in women, it would explain why women end up having a restless night.
Lead author of the study, J. Todd Arnedt, Ph.D., said, “Some women who experience disrupted sleep from alcohol may be less likely to use alcohol in larger quantities, others may be more likely. Determining the role of sleep in who does and does not go on to develop problem drinking, for example, is a question of considerable scientific interest.”
The study was funded by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) and study results will be published in the May 2011 issue of Alcoholism: Clinical and Experimental Research.
†A blood alcohol test directly measures blood alcohol concentration (BAC) and is the most accurate method for testing a person’s blood alcohol content. A breathalyzer test estimates blood alcohol concentration or content indirectly by measuring the amount of alcohol in a person’s breath (breath alcohol concentrate or BrAC).
The Bottom Line
As we’ve all probably seen or experienced, alcohol affects women differently than men. Part of this relates to our size but also to our physiology. Men have more muscle mass and water than women and this effects how quickly alcohol is metabolized.
In measured doses, alcohol has health promoting effects. However, in women this benefit equates to just one drink a day and in men, two drinks. If you’re not sure what constitutes a healthy attitude toward alcohol, take the Rethinking Drinking online quiz developed by the NIAAA.
The key thing to remember is that alcohol impairs our cognitive function. This study also pointed out that impairment occurs not only the night out drinking but even the next morning. As the authors pointed out, women may be at particular risk for experiencing next day impairing effects of alcohol that are due to sleepiness.
A final word, if you are drinking, please be careful about driving. In a woman weighing 140 pounds, just 2 drinks (e.g., two 5-ounce glasses of wine) can put her over the legal drinking limit. Assess your Breath Alcohol Concentration by taking this quick online test.