Middle-aged adults who avoid alcohol altogether, and those who consume the equivalent of seven glasses of wine or more a week are both more likely than light drinkers to develop dementia in their later years, a long-term British  study suggests, Reuters reports.

The increased risk of dementia with heavy drinking may be directly caused by nutritional deficits and the toxic effects of alcohol in the brain. It may also indirectly be  caused by disorders that are common among heavy drinkers like diabetes, high blood pressure and stroke, said lead study author Severine Sabia of Paris-Saclay University in France and University College London in the UK.

Abstinence is also associated with a higher likelihood of having heart disease or diabetes. This explains part of the increased dementia risk for teetotalers, the study found.

Abstinence may also be tied to dementia in people who stopped drinking due to misuse or addiction, Sabia explained to Reuters.

The study

The researchers followed 9,087 adults participating in a long-term study in the UK for an average of 23 years with five assessments of alcohol consumption between 1985 and 2004. They also looked at data from questionnaires to assess problem drinking and at medical records of alcohol-related diseases between 1991 and 2017.

During the study, 397 people developed dementia, at an average age of 76, the study team reports in The BMJ.

Results

Compared to these consistent light-to-moderate drinkers, people who maintained long-term abstinence were 74 percent more likely to develop dementia. Those who kept up a heavy drinking habit were 40 percent more likely to develop dementia. When people cut back after middle age, they were 55 percent more likely than the consistent occasional or moderate drinkers to develop dementia.

The study wasn’t designed to prove whether or how drinking habits might impact the development of dementia.

However, the results suggest that guidelines in many countries that set the bar for problem drinking at much higher than 14 units a week may need to be revised to account for the potential dementia risk, the study authors conclude.