One of the largest studies ever conducted on the long-term effects of alcohol consumption suggests that heavy drinking is linked to significant cognitive decline in middle-aged men. The brains of women, however, seem to be protected against the same effects for reasons that aren’t clear.
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Cognitive decline in the study was defined in two ways: a decrease in executive function (the brain’s processing speed and efficiency), and deterioration in memory.
Researchers analyzed data from the Whitehall II cohort study, which began in the mid-1980s with roughly 10,000 British civil servants who agreed to complete lifestyle questionnaires and undergo a physical exam at specified times during a nearly 20-year span. The study design allowed researchers to track effects of lifestyle choices, including drinking alcohol, over extended periods of time.
The study found that middle-aged men (average age 56) who drank 36 grams, the equivalent of about 1.2 fluid ounces, or more of alcohol a day for 10 years experienced greater memory loss and slowing of executive function as compared to “occasional” or “moderate” drinkers who consumed between .03 and 1.1 ounces a day.
To put this in perspective, a typical shot of 80-proof whiskey is 1.5 fluid ounces, 0.6 fluid ounces of which is pure alcohol. So a heavy drinker, as defined in this study, drank at least two shots of their booze of choice a day. If the study participants were wine or beer drinkers, they drank at least 10 fluid ounces of wine or 24 fluid ounces of beer a day to reach the same alcohol level.
The type of alcohol made no difference in the study results; drinking the equivalent of 1.2 or more fluid ounces of alcohol in beer, wine or hard liquor had the same result.
Heavy drinking for women was defined differently due to the differences in how the sexes metabolize alcohol. To qualify as a heavy drinker in this study, a woman had to drink at least 19 grams (0.6 fluid ounces) of alcohol a day—about half of the male level.
Oddly, heavy drinkers among female participants didn’t show nearly the same level of cognitive decline as men.
The study authors didn’t speculate as to why this difference exists, but it’s possible that the hormone, estrogen, plays a role. A study conducted in 2001 by University of California-Davis researchers showed that estrogen acts as a guardian of brain cell health, and higher levels of the hormone are linked to a reduced risk of developing Alzheimer’s disease. Estrogen may also act as a hormonal shield against alcohol toxicity.
It’s worth mentioning that even though this study didn’t show the same toxic effects of alcohol in women’s brains, there are plenty of other reasons to drink in moderation, not the least of which is liver health.
As with any cohort study, this one has a few drawbacks—chief among them that so many factors affect brain health over extended periods, it’s difficult to isolate specific factors, like alcohol consumption, as the true culprit of cognitive decline. On the other hand, this study’s strength is in the numbers. About 10% of men in the study qualified as heavy drinkers—more than 700 participants—and the signs of cognitive decline across this group were consistently significant.
The brains of drinkers in the occasional and moderate categories seemed to weather the years quite well, about the same as people who either quit drinking or chose to not drink at all.
The study was published in the journal Neurology.
You can find David DiSalvo on Twitter @neuronarrative and at his website, The Daily Brain. His latest book is Brain Changer: How Harnessing Your Brain’s Power To Adapt Can Change Your Life.
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