CHICAGO — Almost 1 in 10 U.S. high school seniors have engaged in recent extreme binge drinking — downing at least 10 drinks at a rate that barely budged over six years, according to a government-funded report.

Less severe binge drinking, consuming five or more drinks in a row, has mostly declined in recent years among teens. But for high school seniors, the 2011 rate for 10 drinks in a row — 9.6 percent — was down only slightly from 2005.

The most extreme level — 15 or more drinks in a row within the past two weeks — didn’t change from 2005 to 2011. Almost 6 percent of high school seniors reported recently drinking that amount.

The number of seniors engaging in the most extreme drinking “is really concerning because they’re most at risk for the really severe consequences,” including reckless driving, car accidents and alcohol poisoning, said lead researcher Megan Patrick of the University of Michigan’s Institute for Social Research.

Extreme binge drinking may be a behavior that’s “more entrenched” among some teens, and thus harder to change, Patrick said.

The new report is an analysis of survey results that the university does for the National Institute on Drug Abuse. It’s based on classroom questionnaires given to more than 16,000 high school seniors; a question on extreme binge drinking was added in 2005.

Whites and males were the most likely to engage in all levels of binge drinking, the report found. Students with more educated parents had higher rates of binge drinking than other kids, but lower rates of extreme binge drinking.

Extreme binge drinking was most common in rural areas and the Midwest and least common in the West.

The report was published online Monday in JAMA Pediatrics.

Young adults generally have higher levels of extreme drinking; a 2012 survey by the same group found that more than 1 in 4 people aged 19 to 30 had recently consumed at least 10 drinks in a row and more than 1 in 10 had at least 15 drinks in a row.

A journal editorial says the new report may help explain why hospitalizations for alcohol and drug overdoses among teens and young adults have increased in recent years despite ongoing declines in less severe binge drinking.

In the early 1980s, before all states made 21 the minimum legal drinking age, more than 40 percent of high school seniors said they had recently downed more than five drinks in a row, according to data cited in the editorial.

The 5-plus binge drinking rate steadily declined in more recent years for seniors, to 22 percent in 2011, although it was 24 percent in 2012, according to a previous report from the survey group. The new report has slightly different percentages because it is based on a subgroup of previous surveys. Survey results for 2012 on extreme binge drinking among seniors haven’t been published yet.