Whites in the United States have typically lived longer on average than blacks, but a new study released on Tuesday suggests that gap in life expectancy may be shrinking.

The shift appears to be because fewer African Americans are dying of AIDS and heart disease, but also because more whites are dying in early and mid-adulthood from unintentional injuries - mainly poisonings, including prescription drug overdoses, researchers said.

“For the most part, blacks are making small but important gains in terms of life expectancy,” said Sam Harper of McGill University in Montreal, Quebec, the lead author of the new report, published as a research letter in the Journal of the American Medical Association.

“There’s still quite a large gap in life expectancy for men and women, and that gap is still much larger than we would like it to be,” Harper told Reuters Health.

Using national data including life expectancy tables from the Centers for Disease Control and Prevention, he and his colleagues compared how long white and black men and women were expected to live as of 2003 and 2008.

Over that time, average lifespan increased among all groups. In men, it rose from 75.3 years to 76.2 for whites and from 68.8 to 70.8 for blacks. The greater increase among black men meant that the gap shrank from a difference of 6.5 years of expected life to 5.4 years.

Life expectancy also grew from 80.3 years to 81.2 in white women and from 75.7 to 77.5 in black women - a difference of 4.6 years in 2003 compared to 3.7 years in 2008.

“The gap at the present time is as low as it’s ever been since we’ve been measuring life expectancy,” Harper said.

An increased rate of heart disease in black Americans was still the leading contributor to a lower life expectancy in men and women. But researchers attributed the improvement to some gains in preventing and treating both heart disease and HIV among blacks.

One explanation is that fewer Americans are smoking, driving down rates of cardiovascular disease and certain cancers, according to a researcher not involved in the new study.

“Given that they’re only looking at a five-year period, it’s remarkable the improvements in life expectancy that we’re seeing,” said Ellen Meara from The Dartmouth Institute in Lebanon, New Hampshire, who has studied disparities in life expectancy.

“It’s on the one hand encouraging that (life expectancy gaps) are shrinking,” she told Reuters Health. “But it’s discouraging one of the reasons they’re shrinking has to do (with) an increase in death due to poisoning in whites.”

In whites aged 20 to 54, accidental poisonings surpassed car crashes as the leading cause of death related to unintentional injury during the study period.

“There is a lot of general concern about this problem of increasing overdoses,” Harper said.

Meara said she is also concerned that increasing abuse of prescription drugs, including opioid painkillers, now more prevalent among white Americans will spread to other parts of the population.

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By Genevra Pittman