Heart disease remains the leading cause of death in the U.S., but cancer is likely to surpass it in the next few years—a shift that has already occurred in many higher-income U.S. counties and among certain racial and ethnic groups, according to a study in the Annals of Internal Medicine in December 2018.

Overall, coronary death rates dropped 28 percent between 2003 and 2015, while cancer death rates fell 16 percent. In 2003, heart disease was the leading cause of death in 79 percent of U.S. counties, cancer in 21 percent of them. In 2015, however, heart disease led in 59 percent of counties, cancer in 41 percent.

Cancer is more likely to be the leading killer in high-income counties because they have had larger reductions in coronary death rates than low-income (usually rural) counties, allowing cancer deaths to inch into the lead. Cancer has also already become the No. 1 cause of death among non-Hispanic white, Hispanic, and Asian Americans, while heart disease remains the primary cause among black and Native Americans.