ATLANTA » Middle-aged women account for the fastest-growing share of overdose deaths in the U.S., and their drug of choice is usually prescription painkillers, the government reported today.

"It’s a serious health problem and it’s getting worse rapidly," said Dr. Thomas Frieden, director of the Centers for Disease Control and Prevention, which compiled the data.

For many decades, the overwhelming majority of U.S. overdose deaths were men killed by heroin or cocaine. But by 2010, 40 percent were women — most of them middle-aged women who took prescription painkillers.

Skyrocketing female overdose death rates are closely tied to a boom in the use of prescribed painkillers. The new report is the CDC’s first to spotlight how the death trend has been more dramatic among women.

The CDC found that the number and rate of female prescription drug overdose deaths increased by around 400 percent from 1999 to 2010. For men, the increases were around 250 percent.

Overall, more men still die from overdoses of painkillers and other drugs; there were about 23,000 such deaths in 2010, compared with about 15,300 for women. Men tend to take more risks with drugs than women, and often are more prone to the kind of workplace injuries that lead to their being prescribed painkillers in the first place, experts say.

But the gap between men and women has been narrowing dramatically.

A jump was also seen in visits to hospital emergency rooms. Painkiller-related ER visits by women more than doubled between 2004 and 2010, the CDC found.

Studies suggest that women are more likely to have chronic pain, to be prescribed higher doses, and to use pain drugs longer than men. Some research suggests women may be more likely than men to "doctor shop" and get pain pills from several physicians, CDC officials said.

But many doctors may not recognize these facts about women, said John Eadie, director of a Brandeis University program that tracks prescription-drug monitoring efforts across the United States.

The report calls for "a mindset change" by doctors, who have traditionally thought of drug abuse as a men’s problem, he said. That means doctors should consider the possibility of addiction in female patients, think of alternative treatments for non-cancer chronic pain, and consult state drug monitoring programs to find out if a patient has a worrisome history with painkillers.

The CDC report focuses on prescription opioids like Vicodin and OxyContin and their generic forms, methadone, and a powerful newer drug called Opana, or oxymorphone.

CDC researchers reviewed death certificates, which are sometimes incomplete. In only a fraction of cases were specific drugs identified. Sometimes a combination of drugs was involved in deaths, like painkillers taken with tranquilizers.

It was not always clear which deaths were accidental overdoses and which were suicides, CDC officials said.

One striking finding involved the age of women: The greatest increases in drug overdose deaths were in women ages 45 through 64.

It’s an age group in which more women are dealing with chronic pain and beginning to seek help for it, some experts suggested.

Many of these women probably were introduced to painkillers through a doctor’s prescriptions for real pain, such as persistent aches in the lower back or other parts of the body. Then some no doubt became addicted, said Dr. Andrew Kolodny, a psychiatrist who specializes in addiction at Maimonides Medical Center in New York City.

There aren’t "two distinct populations of people being helped by opioid painkillers and addicts being harmed. There’s overlap," said Kolodny, president of a 700-member organization named Physicians for Responsible Opioid Prescribing.