MILWAUKEE — Would that crisp Chardonnay or cool refreshing lager go down as guiltlessly if you knew that every sip contributed, imperceptibly, to the shrinkage of your brain?

A new study has found that over time, drinking alcohol, whether moderately or heavily, was associated with decreased brain volume.

And while heavy drinkers had significantly less brain volume than light or moderate drinkers, only abstainers were found to have no alcohol-related brain atrophy. The effect was the greatest in women.

Whether the loss of brain volume actually was caused by alcohol, and whether it contributed to any decreased cognitive function, remains to be seen.

But the study is the latest cautionary note in the perplexing issue of whether moderate alcohol consumption is good for one's health. It raises the question of whether drinking may be good for the heart but not so good for the brain.

"That's the big question," said lead author Carol Ann Paul, a researcher with Wellesley College. "I would be reluctant to tell people not to enjoy their drink a day. But that is something to think about."

The research, which included MRI brain scans of 1,839 people who are part of a Framingham study, was presented Wednesday at the American Academy of Neurology annual meeting.

Based on their drinking habits, the people, who ranged in age from 34 to 88, were divided into five groups: nondrinkers; former drinkers; low drinkers (one to seven drinks a week); moderate drinkers (eight to 14 drinks a week); and heavy drinkers (more than 14 drinks). Their average age was 61.

Compared with the nondrinkers, all of the groups had progressively greater amounts of decreased brain volume, with the biggest decrease in the heavy drinkers. The heavy drinking group had a 1.25 percent decrease in brain volume.

Brain volume decreases somewhat as people age. A loss of 1.25 percent is approximately equivalent to one to two years of normal aging, Paul said.

A subgroup of people in the study who had a 12-year history of heavy drinking had an average 1.6 percent reduction in brain volume.

While, in general, decreased brain volume is associated with decreased cognitive function, the study did not measure that, said Ann Helms, an assistant professor of neurology at the Medical College of Wisconsin.

"It (the study) is a valuable observation," said Helms, who was not a part of the study. "But we need to say, 'What is the cognitive effect of this?"'

Helms said the study raises an interesting question about the role of alcohol in health.