Drinking any amount of alcohol likely increases the risk of dementia, suggests the largest combined observational and genetic study to date, published online in BMJ Evidence Based Medicine.
Even light drinking-generally thought to be protective, based on observational studies-is unlikely to lower the risk, which rises in tandem with the quantity of alcohol consumed, the research indicates.
Current thinking suggests that there might be an ‘optimal dose’ of alcohol for brain health, but most of these studies have focused on older people and/or didn’t differentiate between former and lifelong non-drinkers, complicating efforts to infer causality, note the researchers.
To try and circumnavigate these issues and strengthen the evidence base, the researchers drew on observational data and genetic methods (Mendelian randomization) from two large biological databanks for the entire ‘dose’ range of alcohol consumption.
These were the US Million Veteran Program (MVP), which includes people of European, African, and Latin American ancestry, and the UK Biobank (UKB), which includes people of predominantly European ancestry.
Participants who were aged 56–72 at baseline, were monitored from recruitment until their first dementia diagnosis, death, or the date of last follow-up (December 2019 for MVP and January 2022 for UKB), whichever came first. The average monitoring period was 4 years for the US group, and 12 for the UK group.
Alcohol consumption was derived from questionnaire responses-over 90% of participants said they drank alcohol-and the Alcohol Use Disorders Identification Test (AUDIT-C) clinical screening tool. This screens for hazardous drinking patterns, including the frequency of binge drinking (6 or more drinks at a time).
In all, 559,559 participants from both groups were included in observational analyses, 14,540 of whom developed dementia of any type during the monitoring period:10,564 in the US group; and 3976 in the UK group. And 48,034 died: 28,738 in the US group and 19,296 in the UK group.
Observational analyses revealed U-shaped associations between alcohol and dementia risk: compared with light drinkers (fewer than 7 drinks a week) a 41% higher risk was observed among non-drinkers and heavy drinkers consuming 40 or more drinks a week, rising to a 51% higher risk among those who were alcohol dependent.
