The gap in life expectancy between black and white Americans is smaller than it has ever been, thanks largely to a decline in the number of deaths resulting from heart disease and HIV infection, a new analysis has found.

That’s the good news. The bad news is that the gap is still large: A black baby boy born today can expect to live 5.4 fewer years, on average, than his white counterpart, and a black baby girl will die 3.7 years earlier, on average, than her white counterpart.

What’s more, the narrowing of the gap between 2003 and 2008 is due in part to a troubling development among whites: They are more likely than in the past to die from overdoses of powerful prescription medications like OxyContin and Vicodin, along with other unintentional poisonings.

The report, published in Wednesday’s edition of the Journal of the American Medical Assn., is based on government data on U.S. deaths in 2008, the most recent year that was available at the time of the study.

Since 2003, life expectancy “improved for everybody, but it improved a little bit more for blacks than it did for whites,” said epidemiologist Sam Harper of McGill University in Montreal, senior author of the report.

The life expectancy for black men in 2008 was 70.8 years, up from 68.8 years in 2003 but still well below the 76.2 years for white men (who had an average life span of 75.3 years in 2003), Harper and his colleagues found. Life expectancy for black women rose from 75.7 to 77.5 years, while the life span for white women grew from 80.3 years to 81.2 years.

The study included data only for non-Latino whites and non-Latino blacks. The government has only recently compiled the first life-expectancy tables for Latinos, who have an edge of several years over non-Latino whites for reasons that are not yet clear.

Tables for Asians, whose life expectancy is believed to be the best of all groups living in the U.S., and for Native Americans are not yet available, Harper added.

Harper and his colleagues examined data on the number and causes of deaths among the U.S. population in 2003 and 2008. Those figures, from the Centers for Disease Control and Prevention’s National Center for Health Statistics, were paired with U.S. census data to calculate death rates for blacks and whites of each gender. Life expectancy was then calculated as a summary of the death rates at each age.

An analysis like this reveals how death rates from different causes vary between races and how they have shifted over time, but it says nothing about the sociological and medical reasons for those changes, Harper said. Scientists have a lot of educated guesses, though.

Blacks have higher rates of obesity, diabetes and hypertension — all risk factors for cardiovascular disease and stroke, the No. 1 and No. 4 leading causes of death in this country. Studies have documented that blacks are treated less aggressively than whites for heart problems, said Dr. James McPherson, medical director of the Los Angeles Cardiovascular and Thoracic Surgery Group and a spokesman for the American Heart Assn.

Blacks are also less likely to have health insurance, so they are apt to be treated later in the course of heart disease than those with regular access to care, McPherson added.

“I’m happy to see the gap is narrowing, but it is still pretty substantial,” he said.

An unsettling part of the new report is the uptick in deaths from unintentional poisoning among whites, predominantly in middle-aged white men.

Data from the CDC show that poisonings outnumbered deaths from motor vehicle accidents for the first time in 2008. The increase in poisonings appears to be driven by a rise in the number of deaths from prescription medications to treat pain and anxiety problems, an investigation by the Los Angeles Times found last year, citing preliminary CDC data from 2009.

The inequality in life spans has been documented for more than a century. In 1900, when life tables for blacks and whites were first compiled, the gap stood at more than 14 years, said Elizabeth Arias, a demographer with the National Center for Health Statistics in Hyattsville, Md. A black man could expect to live just 32.5 years and a black woman 33.5 years. By contrast, white men lived an average of 46.3 years and women lived an average of 48.3 years.

Infectious diseases were the biggest killers then, but that changed as public health campaigns improved sanitation and vaccines, antibiotics and other medical improvements allowed more people to survive childhood and reach middle age.

Blacks have gained ground on whites throughout the century, albeit with setbacks here and there. But the gap has never disappeared.

It even widened in the 1980s, when AIDS and homicide disproportionately killed blacks, Harper said.

rosie.mestel@latimes.com