A 2003 study in the Journal of the American Medical Association found that two or more alcoholic drinks per day increased dementia risk by 22 percent, while lighter drinking was associated with up to a 54 percent lower risk compared with abstinence. That finding helped popularize the notion that moderate drinking could protect the brain.
"I remember reading that JAMA paper 20-some odd years ago and thinking, I really ought to try and have a glass of wine every day," said Dr Joel Gelernter, a professor of psychiatry, genetics and neuroscience at the Yale University School of Medicine.
Observational research consistently showed that light-to-moderate drinkers had lower dementia rates. However, more rigorous analyses have since suggested that the apparent benefit was an artifact of how the studies were designed, often comparing drinkers to a group of non-drinkers that included former heavy drinkers who had quit due to health problems.
"This idea of the J-shaped curve was really pretty darn reproducible in many studies," said Dr Kristine Yaffe, a professor of psychiatry, neurology and epidemiology at the University of California, San Francisco. But, she added, "I think more recently, people have debunked that J."