WASHINGTON — As Americans aged over the last two generations, they drank less alcohol. And the younger generation of adults drank less heavily than the ones before it, according to the first analysis of alcohol-consumption trends over adult life spans.

By the time they reached their 80s, more than 40 percent of men and 60 percent of women said they didn't drink at all, according to a study in the August issue of The American Journal of Medicine.

Over time, beer drinkers generally shifted to wine, the study found, and the younger generation drank less hard liquor than the older ones did. At the same time, more and more adults aged into moderate drinkers by federal dietary standards. They define moderate drinking as two drinks per day for men and one per day for women.

"They've understood that a little alcohol is OK but a lot is not good," said Curtis Ellison, a co-author of the report and a professor of medicine and public health at Boston University School of Medicine.

At the same time, rates of problem drinking remained unchanged, Ellison's team found. Nearly 13 percent of men and 4 percent of women reported problems across the study span.

"It seems they just can't get over their problems with alcohol," Ellison said.

Researchers relied on estimates of alcohol consumption reported every two to four years from 1948 through 2003 for a famous and massive study of lifetime health called the Framingham Heart Study. The alcohol analysis involved 8,600 of its participants, born from 1900 through 1959.

The participants' experiences with alcohol reflect trends for most of the last century.

Women consistently drank less than men, the study found. Heavy drinking dropped with age for men but fell less markedly for women.

By their mid-70s, men were drinking half the beer they'd drunk in their mid-30s, and the decline among women was similar.