Study Finds Heavy Drinking May Increase Risk for Dementia

Study Finds Heavy Drinking May Increase Risk for Dementia

Abstaining from alcohol long-term may also up your risk, but the reasons are complex.

Drinking heavily—or abstaining entirely—during one’s middle years are associated with an increased risk of developing dementia later in life, compared with drinking moderately, according to a study published in August 2018 in the medical journal BMJ.

The researchers tracked 9,087 people in England starting when they were 35 to 55 years old and assessed their drinking habits and incidence of dementia over an average of 23 years of follow up.

They found that compared with moderate drinking, drinking no alcohol and drinking heavily were both linked to dementia. Moderate drinking was defined as consuming between 1 and 14 units of alcohol per week, while heavy drinking meant imbibing more than 14 units per week.

For those drinking more than 14 units a week, an increase of 7 units of alcohol each week was associated with a 17 percent greater risk of dementia, and long-term alcohol consumption above 14 units a week increased the risk of dementia by 40 percent compared with long-term moderate consumption. Those with a history of requiring hospital admission for alcohol-related disease had a four times higher risk of dementia.

Measuring alcohol intake
To quantify alcohol intake, the study authors relied on a measure called the alcohol unit, which is defined in the UK as 8 grams of pure alcohol and is roughly the quantity that an average adult’s body can process in an hour.

The number of units in a drink depends on the alcohol content and the size of the drink. Roughly speaking, a 6-ounce glass of wine and a 19-ounce British pint of beer are each about two units. A 1-ounce shot of liquor is about 1.5 units.

Put another way, 14 units of alcohol—the upper limit for a week’s worth of alcohol according to current public health guidelines in the UK—translates into about six pints of beer or six glasses of wine.

Should you stop—or start—drinking?
The available evidence on the relationship between alcohol use and dementia are mixed, but some research suggests that moderate drinking is associated with a decreased risk of dementia. The authors of the BMJ study noted that they found no evidence that drinking between 1 and 14 units of alcohol a week increases risk of dementia.

That said, study co-author Séverine Sabia, PhD, an epidemiology researcher with French health organization Inserm and the Université Paris-Saclay, noted that the study’s finding on abstainers “should not motivate people who do not drink to start drinking alcohol.” Sabia, in an email interview with Sharecare, cited “adverse effects of alcohol on mortality, cirrhosis of the liver and cancer” as reasons not to start drinking in the hopes of staving off cognitive decline.

As for why why abstinence and excessive drinking were linked to increased risk of dementia while moderate drinking was not, the researchers had some theories, and noted that the underlying mechanisms were probably different for the different groups.

“In terms of biology, people who drink in moderation tend to have lower levels of inflammation or higher levels of good cholesterol,” Sabia explained. “But these people also tend to be more healthy and socially engaged, and that might lead to lower risk of dementia.”

As for the negative effect that heavy alcohol intake appears to have on the risk of dementia, Sabia noted that it may involve nutritional deficiency as well as the “direct neurotoxic effects of ethanol and the indirect negative impacts contributed by the increased risk of diabetes, hypertension and stroke” from heavy drinking.

It’s important to note that, as an observational study, the research is unable to confirm a cause-and-effect relationship between drinking and dementia. But the findings are helpful in that they reaffirm some of what’s currently understood about the health effects of alcohol: Too much is always detrimental, the benefits of total abstention are unclear—but a modest amount may be a reasonable part of an overall healthy lifestyle.

Medically reviewed in August 2018.

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