Drinking Too Much—or Not at All—May Be Linked to Dementia

The results of a new study should be interpreted cautiously, experts say.

Posted Aug 07, 2018

William Perugini/Shutterstock
Source: William Perugini/Shutterstock

Both drinking excessively in midlife and abstaining from alcohol entirely were associated with an increased risk of later dementia in a long-term study of more than 9,000 adults. The study is an important step for better understanding risk factors for dementia, experts say, but they caution that it may be too early to make sweeping statements about alcohol’s effect on the aging brain.

The study, published August 1 in the British Medical Journal, tracked British civil servants for an average period of 23 years, beginning in 1983. At the study’s inception, participants were between 35 and 55 years old. Researchers used hospitalization records, mortality registers, and recorded use of mental health services to determine participants’ dementia status and assessed their alcohol consumption at regular intervals with questionnaires. “Moderate” alcohol consumption was defined as 1 to 14 “units” of alcohol per week, with one unit equal to 10 milliliters. Translated to standard drinks in the U.S., that would top out at roughly eight drinks per week.

“Our main finding is that among those drinking above 14 units of alcohol per week, the risk of dementia increases as the number of alcohol units consumed increases,” says lead author Séverine Sabia, a researcher at Inserm, the French National Institute of Health and Medical Research. “Every seven-unit-a-week increase in consumption was associated with a 17 percent increase in dementia risk.” Those who drank to the point of hospitalization had an increased risk of 400 percent. Total abstainers, on the other hand, were nearly 50 percent more likely than moderate drinkers to develop dementia. Both groups—heavy drinkers and abstainers—showed increased risk even after controlling for age, gender, and socioeconomic factors.

The findings echo past research showing a “J-shaped” curve between alcohol and dementia risk, where moderate consumption is associated with the lowest risk, says Sevil Yasar, an associate professor at Johns Hopkins Medicine who studies dementia and cognitive decline. “Most of the studies were short follow-ups,” she adds. “This is the first and only study to find that over such a long period of time.”

But the study, while well-designed, has its drawbacks, she says—one of which is its reliance on self-reported alcohol consumption. “People have a tendency to under-report,” she says. And since its subjects were all civil servants, it’s important to ask if the findings can be generalized to the rest of the world—or even the rest of the United Kingdom—and what recommendations, if any, can be made based on the data.

“The easy part is when you’re an excessive drinker, you should definitely cut down,” Yasar says. “But if you’re an abstainer, do you need to start drinking?” That’s less clear, she says. Moderate alcohol consumption has been shown to correlate with other positive outcomes—including a decreased risk of cardiovascular disease, another known dementia risk factor—but also with health conditions such as substance abuse disorder and breast cancer.

“You have to take into account every person’s medical blueprint” before making sweeping recommendations about alcohol consumption, Yasar explains. The current study concluded that comorbid cardiometabolic factors could explain some—though not all—of the increased dementia risk in the abstainer group. “Maybe we need to focus more on lowering blood pressure or reducing the risk of a heart attack” as a way of decreasing dementia risk in the general population, she says.

Ultimately, while the study adds to the data finding an association between alcohol consumption and dementia, it was only observational and should not be interpreted as showing a direct causal link. It “does not indicate that drinking reduces your risk, and is not evidence that taking up drinking alcohol is good for you,” says Katy Stubbs, a communications officer at Alzheimer’s Research UK. “People may have reduced intake due to underlying health concerns not captured in this study, and we also don’t know about drinking patterns in early adulthood” since the study only started following subjects in midlife.

While more research would be beneficial to the field, it’s hard to say what that research could look like, says Anya Topiwala, a clinical researcher at the University of Oxford who also studies the relationship between alcohol and cognitive decline. “I struggle to see how a randomized controlled trial—the gold standard in medicine to determine a genuine effect—is practical or ethical,” says Topiwala, who was not involved in the current study. “Other types of research, [particularly those] which examine the brain more directly, will be needed to shed more light.”

“Ultimately, I think the jury remains out with regards to any beneficial effect of moderate drinking on the brain,” she says.

Still, the emphasis on midlife risk factors is important, Yasar notes.

“Changes in the brain start 20 years before you even have symptoms [of dementia],” she says. “That’s why there’s been more and more interest in modifiable lifestyle risk factors” like weight, blood sugar levels, and cardiovascular health. Evidence suggests that “you can impact your risk of developing dementia with what you do in midlife.”