In 2015, the average American’s life expectancy was cut short by a little more than a month. For the first time in two decades, U.S. life expectancy for someone born in 2015 fell from 78.9 years to 78.8 years (National Center for Health Statistics, December 8, 2016). Of the top ten leading causes of death in the U.S., eight showed an increase. This is a big deal, says Philip Morgan, a demographer at the University of North Carolina, Chapel Hill. In an NPR interview, Morgan said, There’s not a better indicator of well-being than life expectancy. The fact that it’s leveling off in the U.S. is a striking finding.

The most notable increase in mortality was from heart disease and stroke. For years, deaths from cardiovascular disease had been in a steady decline, but in 2015 jumped by almost 1%. The obesity epidemic and an increase in diabetes are contributing factors. Experts also say that doctors may have simply reached the limit on what they can do for heart disease with today’s technology.

The second leading cause of death was from cancer.  Overall, however, cancer deaths decreased by 1.7%. This is probably because of earlier and more accurate diagnosis, breakthrough treatments, and the fact that fewer people are smoking.

The biggest increase in deaths was from Alzheimer’s disease, up 15.7% from the previous year. This can be blamed, in large part, on an increase in earlier and more widespread recognition and reporting of the disease as a cause of death.

Respiratory disease, kidney disease, and diabetes account for a significant increase in overall mortality. Also, the growing epidemic of prescription opioid pain killers and heroin abuse has had an impact. Plus, suicide rates have increased.

Dr. Peter Muennig, a professor of health policy and management at Columbia University’s Mailman School of Public Health said the decline [in life expectancy] was a ‘uniquely American phenomenon’ in comparison to other developed countries, like Japan or Sweden. To see life expectancy decrease, said Muennig, is very alarming (New York Times, December 8, 2016).

The decline in life expectancy could be a blip, but even if it’s flat, we have a problem,” said Jonathan Skinner, a professor at the Dartmouth Institute of Health Policy and Clinical Practice (USA TODAY, December 8, 2016). The 2015 statistics are shocking and difficult to explain, described by some experts as a mystery.”

Shortly after this report was released, a timely article was published in JAMA (December 13, 2016). Instead of looking at causes of death from a national perspective, mortality rates were analyzed for 3110 counties or groups of counties. Large between-county disparities were evident for every cause of death.

For example: Cardiovascular disease mortality tended to be highest along the southern half of the Mississippi River, while mortality rates from self-harm and interpersonal violence were elevated in southwestern states, and mortality rates from chronic respiratory disease were highest in counties in eastern Kentucky and western Virginia. Cancer deaths were high in counties in several southern states and western Alaska, but low in many counties in Idaho, Wyoming, and West Texas. Counties in western states had much lower mortality rates for several causes when compared to counties in Appalachia and the South.

Using this data, physicians and county public health departments are now in a better position to tailor programs to address the needs of their local communities. Knowing that the causes of death vary so dramatically from county to county suggests that finding ways to improve life expectancy in the U.S. need not be such a mystery.