FRANKFORT, Ky. (AP) — Placing much of the blame on smoking, a study chronicling the ongoing health crisis in Appalachia has concluded that the 13-state region suffers from a growing disparity in infant mortality and life expectancy, two key indicators of "a nation's health and well-being."

The study , published in the August issue of Health Affairs, compared infant mortality and life expectancy rates in Appalachia with the rest of the United States between 1990 and 2013. It found while the rates were similar in the 1990s, by 2013 infant mortality across Appalachia was 16 percent higher than the rest of the country while life expectancy for adults was 2.4 years shorter.

While the region has been the focus of the opioid epidemic in recent years, the study found one of the biggest culprits was likely the prevalence of smoking and the region's tendency to be "more accepting of tobacco use as a social norm." Gopal K. Singh, a co-author of the study and a senior health equity adviser with the Health Resources and Services Administration, noted nearly 20 percent of Appalachian women report they smoked during pregnancy. In the rest of the country, it's 8 percent.

"Smoking takes a tremendous toll on the health of Appalachians," the authors wrote.

The study used the federal Appalachian Regional Commission to define the region, which covers 428 counties across 13 states. It includes all of the counties in West Virginia along with some counties in Alabama, Georgia, Kentucky, Maryland, Mississippi, New York, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee and Virginia.

Heart disease, cancer and other respiratory illnesses were among the leading causes of death throughout the study period, all of which can be caused by using tobacco. Kentucky and West Virginia have some of the highest smoking rates in the nation coupled with some of the lowest cigarette taxes.

In Kentucky, state lawmakers passed a law requiring health insurance companies to cover tobacco cessation medications that have been approved by federal regulators. But they failed to pass a bill that would have banned tobacco products from public school campuses. Just 36 percent of Kentucky's 173 public school districts ban all tobacco products on campus and at school-sponsored events.

"What this report shows is the extreme damage tobacco is causing our people and how we are getting hammered by it worse than any other place in this country," said Ben Chandler, president and CEO of the Foundation for a Healthy Kentucky.

The study found that drug overdoses accounted for 6.3 percent of the life expectancy gap between 2009 and 2013, and it was a likely explanation for why the life expectancy of white women declined between 1990 and 2004 while increasing among white women among the rest of the country.

Singh noted the study only includes date through 2013. Since then, drug overdose deaths in Kentucky and elsewhere have soared because of the availability of heroin and fentanyl, a synthetic opioid that is much more powerful than heroin.

"The contribution of drug overdoses could be higher for the most recent time period," he said.

Other causes included accidental deaths, such as car wrecks. The study noted 30 percent of "unintentional injury deaths" in Appalachia are from car wrecks, which "contributes substantially to the life expectancy gap."