Researchers have known for some time that those who can afford better health care are generally healthier than people who can’t afford it. By studying the death certificates from more than 3,000 U.S. counties from 1980 to 2014, they now know who is most likely to die from drug overdoses, who is most likely to die from diabetes or other chronic diseases, and where they live. Dr. Christopher Murray and others at the University of Washington found a significant variation in death rates among counties for all causes of death, according to their study, published in the Journal of the American Medical Association. “We found that different causes matter more in different parts of the country,” Murray said. “So out West, for example, in the U.S., violent death is more common, whereas heart disease is more common in the Southeast. And deaths from drugs are much more common in West Virginia or Kentucky.” Heart disease is the leading cause of death overall in the U.S., but Murray says the risk of heart disease and other diseases differ significantly among communities, highlighting stark health disparities across the nation. “We really need to understand why there’s such variation in how long people live, and what causes children, adults, and older people to die at such different levels in different communities,” Murray said. Each of the U.S. states is divided into counties with their own local governments. The researchers also found health differences between counties in the same state. What’s more, Murray says, the gaps in life expectancy from one county to another are increasing. “It’s incredibly important for us to understand why different communities live very different life spans. And the variation across the U.S. is enormous,” he said. “There’s more than 20 years’ difference across communities, and we really need to understand that.” Murray and other researchers say their work could be used to address causes of death in particular areas and improve Americans’ overall health.