Why has U.S. life expectancy stalled out?

Life expectancy in the United States has stalled for three straight years, the government announced Wednesday.

A child born last year can expect to make it to 78 years and 9½ months - the same prediction made for the previous two years.

In most of the years since World War II, life expectancy in the U.S. has inched up - thanks largely to medical advances, public health campaigns and better nutrition and education. The last time it was stuck for three years was in the mid-1980s.

It's not clear why life expectancy has been flat lately, but suicides and fatal drug overdoses probably are playing a role, experts believe.

Some researchers have wondered if U.S. life expectancy will peak, due to the nation's obesity problem and other factors. But there is no evidence that's happening now, said Robert Anderson of the Centers for Disease Control and Prevention.

S. Jay Olshansky, a public health professor at the University of Illinois-Chicago, agreed.

"It's too early to tell. Three years does not a trend make," he said.

The United States ranks below nearly 40 other countries in life expectancy, according to the World Bank. Japan and Iceland are at the top of that list, at more than 83 years.

U.S. health officials come up with the life expectancy figure each year by looking at how old people were when they died and the cause of death. They use statistical modeling to predict how long people born today will live if current trends continue.

The CDC report is based on all 2014 death certificates. There were about 2.6 million deaths, or about 29,000 more than the previous year. The increase reflects the nation's growing and aging population.

Other findings:

• Infant mortality dropped again slightly, to a record low of 5.8 per 1,000 births.
• The 10 top causes of death remained the same: heart disease, cancer, respiratory diseases such as emphysema and bronchitis, accidents and unintentional injuries, stroke, Alzheimer's disease, diabetes, flu and pneumonia, kidney disease and suicide.
• Death rates fell significantly for five causes, including the top two -- heart disease and cancer.
• The largest increase was in Alzheimer's disease, which climbed eight percent.
• Suicides and unintentional injuries -- a category that includes falls, traffic accidents and drug overdoses -- each went up by about three percent.

Overdoses are driving up those death rates, said Ian Rockett, a West Virginia University researcher who studies overdoses and suicides.

Drug overdose deaths in the U.S. have been rising for more than 20 years, primarily from the abuse of powerful prescription painkillers including Vicodin and OxyContin. Heroin-related deaths -- though far less common than painkiller deaths -- have also recently spiked.

According to CDC research, people live longer if they practice even one additional healthy lifestyle behavior such as not smoking, eating a healthy diet, getting regular physical activity, and limiting alcohol.

People who engage in all four healthy behaviors are 63 percent less likely to die early compared to people who didn't practice any of the healthy behaviors, the CDC research showed. Steering clear of tobacco -- not smoking -- offered the most protection from dying from all of the causes.