By the year 2020, cancer could be the leading cause of death in the United States, outpacing heart disease. A new study says the shift is thanks to advances in drugs and technology that are making a huge impact against heart disease.

For the study, researchers looked at U.S. death records from 2003 to 2015. Overall, death rates dropped about 1 percent per year. Deaths from heart disease fell nearly 3 percent per year, while cancer deaths decreased by about 1.5 percent per year, the findings showed.

It’s important to emphasize both numbers, according to Dr. Michael Fradley, a cardiologist at Moffitt Cancer Center.

“While cardiovascular disease mortality is falling more quickly, cancer mortality has also dramatically improved over the last few decades,” Fradley said. “Mortality is improving for both diseases, which is important to recognize.”

Although deaths from heart disease during the study period fell 28 percent, the drop was more significant in high-income counties than in poorer ones -- 30 percent versus 22 percent, the investigators found.

This difference suggests the change from heart disease to cancer as a leading cause of death will take longer in poorer areas.

The cancer mortality rate also dropped, though less dramatically: It declined by 16 percent, with an 18 percent drop seen in high-income counties versus 11 percent in low-income.

According to the researchers, lower-income areas may see a slower shift in the cause of death due to socioeconomic, geographic, demographic and other factors that influence health and death.

The researchers also compared shifts in patterns for racial and ethnic groups. Here, they found that among Asian Americans, Hispanics and whites, cancer replaced heart disease as the leading cause of death. However, a similar pattern was not seen among American Indians/Alaska Natives or African Americans.

The report, published Nov. 12 in the Annals of Internal Medicine, found that in 2016, in the United States, heart disease claimed more than 635,000 lives and cancer took nearly 600,000, according to the U.S. Centers for Disease Control and Prevention. Accidents, the third-leading cause of death, claimed a little more than 160,000 lives. The authors contribute the change, at least in part, to people living longer.