Drinking even "moderate" amounts of alcohol increases dementia risk, US research suggests.
The findings, presented at an international conference, challenge the notion that some alcohol could be good for ageing brains.
People who stick to recommended alcohol limits are still at risk, as well as bingers and heavy drinkers, according to the work.
The study tracked the health over 20 years of 1,300 women in their mid-60s.
Dementia is a chronic or persistent disorder of the mental processes marked by memory disorders, personality changes, and impaired reasoning.
The risk, ranging from mild cognitive impairment to full blown dementia, was higher among those who reported drinking more alcohol.
Women who switched from abstinence to drinking over the course of the study also increased their risk.
Those who drank alcohol "in moderation", meaning seven to 14 alcoholic drinks a week, were also more likely to develop problems with memory and brain functioning that can be a warning sign of future dementia.
The lower end of this range falls within the UK's recommended limit for women, but since alcohol measures in the US are larger than in the UK, 14 drinks a week would exceed this UK weekly cut off.
And since the study only looked at women, it is not possible to say if the same link will apply in elderly men.
Researcher Tina Hoang, of the Veterans Health Research Institute in San Francisco, said: "In this group of older women, moderate alcohol consumption was not protective.
"Clinicians should carefully assess their older patients for both how much they drink and any changes in patterns of alcohol use."