Nightcaps Make Sleep—and Cognitive Problems—Worse

Far from promoting restful slumber, a drink can cause fitful, poor-quality sleep that impairs brain function.

About 70 million Americans suffer from chronic sleep problems, according to the Centers for Disease Control and Prevention—and new research suggests that sipping a sedating alcoholic drink before bed isn’t going to help.

A nightcap may make you feel relaxed and drowsy, but it plays havoc with your sleep. It alters normal sleep cycles in ways that impair your ability to form memories and concentrate and leaves you tired and cranky the following day, according to an extensive review of research on the effects of alcohol on sleep published in the April 2013 issue of the journal Alcoholism: Clinical & Experimental Research.

“The review makes it clear that drinking alcohol interferes with normal sleep architecture and negatively affects brain function, especially in older individuals,” says psychiatrist E. Nalan Ward, MD, Director of the MGH West End Clinic, which delivers outpatient addiction services. “Far from helping ensure a deep and restful night’s sleep, drinking even as many as six to eight hours before bedtime is associated with greater likelihood of fragmented sleep, frequent awakenings, alterations of natural cycles of activity in the brain, and disruptions of brain functions such as memory, judgment and decision-making. Alcohol is associated with slowed breathing that can reduce the flow of oxygen to the brain, and it also makes you more vulnerable to sleep disorders.

“If you are experiencing problems falling or staying asleep, see your health care provider for an assessment to ensure that your sleep problems are not associated with a medical condition, a mood disorder such as depression, or a medication that you are taking. If these factors are ruled out, adopting lifestyle and behavioral changes may help you achieve a more restful night’s sleep without resorting to a nightcap. Many strategies—such as exercising regularly or quitting smoking—not only help you avoid the negative effects of alcohol, but also promote brain health in general.”

Initial benefits fade

The researchers’ analysis of alcohol’s effects on sleep suggests that drinking affects the sleeping brain in two stages. Initially, the alcohol reduces the time it takes to fall asleep and promotes deep, slow-wave sleep in a dose-dependent manner (i.e., the more alcohol, the deeper the sleep). These effects may help explain the myth that alcohol is a sleep aid. Slow-wave sleep—the phase associated with the transfer of short-term memories to long-term storage—seems to benefit memory and is a restful, restorative sleep phase that promotes tissue repair and strengthens the immune system. But this phase of sleep also increases vulnerability to sleep disorders such as sleepwalking and sleep apnea (a disorder characterized by loud snoring and the closure of airways during sleep that reduces intake of oxygen).

Moderate and higher doses of alcohol (the equivalent of about two 12-oz. beers or more) also act to delay rapid eye movement, or REM, sleep. REM sleep—the dream stage of sleep during which the brain organizes and connects information and stores it more efficiently—is important for memory and concentration. Delayed REM sleep is associated with less restful sleep, and is often associated with stress and depression.

About halfway through the night, the adverse effects of moderate and higher amounts of alcohol on sleep become more apparent. The total quantity of REM sleep is decreased, with negative consequences for concentration, memory and motor skills. Slow-wave sleep becomes disrupted, with frequent awakenings, fitful sleep, and greater difficulty falling back asleep. Fatigue, irritability, and daytime sleepiness are more likely the following day.

Effects of age

The negative effects on the brain associated with alcohol are magnified with age. Older people become more sensitive to alcohol as age-related changes in absorption and metabolism lower tolerance to the drug, aggravating symptoms of cognitive decline and making memory problems more likely. Research suggests that even without alcohol, older people wake up more often during the night and get less slow-wave sleep than younger individuals do.

In a paper published in the Jan. 27, 2013 issue of Nature Neuroscience, researchers compared the memory performance of older volunteers to that of younger volunteers before and after a night’s sleep. The two groups did equally well on a memory task prior to going to sleep. However, brain scans indicated that the quality of slow-wave sleep among older participants in their study was 75 percent lower than that of the younger participants, and their ability to recall the memory task the next day was 55 percent worse than that of the younger participants. The link between memory loss and problems with slow-wave sleep in older adults suggests that eliminating alcohol-related disruption of sleep is an excellent strategy for maximizing memory performance in older age.

Improving sleep

To get a more restful night’s sleep, Dr. Ward recommends improving your “sleep hygiene.”

“Among other strategies, try to adhere to a regular sleep schedule, and avoid daytime napping,” she says. “Ensure that your sleep environment is calm and comfortable. Help your brain shut down by lowering the lights and reducing stimulation close to bedtime. Cut down on or eliminate caffeine, alcohol and nicotine. Exercise regularly, but not within four hours of bedtime. Learn relaxation techniques, such as visualization or yoga to reduce stress that may be inter,fering with your sleep.”

It’s also important to keep your alcohol consumption at brain-healthy levels, Dr. Ward cautions.

“Experts calculate one drink as 12 ounces of beer, one five-ounce glass of wine, or one and one-half ounces of 80-proof alcohol,” she explains. “They recommend no more than 14 drinks per week for men up to age 65, and no more than seven per week for women up to 65. Over the age of 65, men should restrict themselves to just seven drinks a week, and women to no more than four.”


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