ATLANTA (AP) — College-age drinkers average nine drinks when they get drunk, government health officials said Tuesday.

That surprising statistic is part of a new report highlighting the dangers of binge drinking, which usually means four to five drinks at a time.

Overall, about 1 in 6 U.S. adults surveyed said they had binged on alcohol at least once in the previous month, though it was more than 1 in 4 for those ages 18 to 34.

And that’s likely an underestimate: Alcohol sales figures suggest people are buying a lot more alcohol than they say they are consuming. Health officials estimate that about half of the beer, wine and liquor consumed in the United States by adults each year is downed during binge drinking.

“I know this sounds astounding, but I think the numbers we’re reporting are really an underestimate,” said Dr. Robert Brewer, who leads the alcohol program at the Centers for Disease Control and Prevention.

The CDC report is based on telephone surveys last year of more than 450,000 adults. They were asked about their alcohol drinking in the past month, including the largest number of drinks they had at one time.

Binge drinking is generally defined as four drinks for women and five for men in a period of a few hours. Binge drinkers ages 18 to 24 reported nine drinks, or one more than the national average of eight drinks.

But those numbers are likely averages for all episodes of binge drinking, Brewer said, citing other studies.

The number of drinks per binge went down with age, to less than six for those ages 65 and older.

Binge drinking may be considered socially acceptable – to many, a fun night out at the bar. And many don’t see it as a sign of a serious drinking problem. Indeed, experts say fewer than 20 percent of binge drinkers would be medically diagnosed as alcoholics.

But health officials say binge drinking accounts for more than 40,000 deaths each year. It contributes to problems like violence and drunk-driving accidents and longer-term issues like cancer, heart disease and liver failure.

Other findings of the report:

-Binge drinking continues to be most common in men, people who have been to college, and those with incomes of $75,000 or more.

-Only about 4 percent of people 65 and older binge drink, far fewer than adults in other age groups. But they do it more often – five times a month, on average. Younger adults average closer to four episodes per month.

-The upper Midwest continues to report the highest prevalence of binge drinking. Wisconsin topped the list in 2010 with nearly 26 percent of adults saying they had at least one binge drinking episode in the previous month. West Virginia, at just under 11 percent, was at the other end of the spectrum.

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Online:

CDC report: http://www.cdc.gov/vitalsigns