Overdoses of drugs, particularly prescription painkillers and heroin, have overtaken AIDS to become the leading cause of death of homeless adults, according to a study of homeless residents of Boston.

The finding came from a five-year study of homeless adults who received treatment from the Boston Health Care for the Homeless Program, though its broad conclusions apply to homeless populations in many urban parts of the United States, the study's author and homeless advocates said.

The tripling in the rate of death by drug overdose reflects an overall rise in pain-killer abuse, said Dr. Travis Baggett of Massachusetts General Hospital, the lead author of the study, to be published next month in the journal JAMA Internal Medicine.

"This trend is happening across the country, in non-homeless populations too," Baggett said. "Homeless people tend to experience in a magnified way the health issues that are going on the general population."

The study, which tracked 28,033 homeless adults from 2003 through 2008, found that of the 17 percent who died during the study period died of drug overdoses while 6 percent died of causes related to HIV, the virus that causes AIDS.

That is a rough reversal of the trend found in a similar study 15 years earlier, when 6 percent of deaths were due to drug overdose and 18 percent due to AIDS.

After the drug overdoses, the second- and third-leading causes of death in the most recent study were cancer, which accounted each for about 16 percent of the deaths.

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