A heroin user prepares to inject himself in New London, Conn. Communities nationwide are struggling with an unprecedented epidemic of opioid and heroin overdose deaths, which are contributing to a sudden increase in Americans' overall mortality rate.  (John Moore/Getty Images)

The long decline in Americans’ death rates has reversed course, according to preliminary 2015 numbers for all causes of mortality as compiled by the Centers for Disease Control and Prevention.

Many factors are implicated in the turnaround, including a rise in deaths from firearms, drug overdoses, accidental injuries, suicides, Alzheimer’s disease, hypertension and stroke.

In a report released Wednesday, the CDC looked at changes in death rates per 100,000 people between 2014 and 2015, adjusting the findings to reflect an aging population as the baby boomers head into their retirement years.

The agency identified gains on the cancer front: The disease is killing Americans at a lower rate. But that medical progress was overtaken by the other factors. Lethal drug overdoses, for example, rose from 14.0 per 100,000 people in early 2014 to 15.2 by mid-2015. And even though heart disease was basically flat, that was a change from the major killer’s years-long decline — a decrease that had helped drive down the overall mortality rate.

Whether the uptick in the death rate is a statistical fluke is unclear. The CDC will have final numbers in December, and one year does not make a trend. But the report echoes other recent research suggesting that these days the American way of life is too often leading to an early death.

“There’s no smoking gun here,” said Farida Ahmad, mortality surveillance lead for the CDC’s National Center for Health Statistics. She calls the increase in mortality “unusual,” noting that it’s the first time since 2004-2005 that the rate went up rather than down.

“It’s something that we’re going to be looking into and watching to see if it holds for 2016. It could be that it’s just a blip as it was 10 years ago,” she said.

The historical trend in health and mortality has largely been a story of medical triumphs and longer lives. For example, in 1950, when rates of infant mortality were much higher than today, the death rate per 100,000 Americans was 1,446. By 2014 the rate had fallen to exactly half that — 723. But the preliminary 2015 numbers show a bump up to 729.5.

Numerous researchers have been focusing on the sharp and unanticipated rise in mortality among whites, particularly white women, in their midlife years. The Washington Post’s own analysis of the nation’s death rates indicates that this increase is pronounced in small cities, small towns and the most rural areas.

[A new divide in American death]

This latest report does not break down deaths by sex, race, geography or other demographic indicators.

“When we’re spending $3 trillion in health care, and we’re seeing mortality rise -- even if this is only a momentary rise -- we need to examine what we’re doing and how we’re doing it," said Ellen Meara, professor of health policy and clinical practice at Dartmouth College. “Clearly we’re doing something wrong.”