Socioeconomic conditions affect the leading cause of death

A population health study recently published in the Annals of Internal Medicine found that socioeconomic conditions affect leading cause of death on a county level. Conducted in response to recent data showing that the United States is transitioning from heart disease to cancer as the leading cause of death, researchers found that heart disease is still more likely to be the leading cause of death in lower-income counties.

The study, “Socioeconomic Differences in the Epidemiologic Transition from Heart Disease to Cancer as the Leading Cause of Death in the United States, 2003 to 2015: An Observational Study,” examined U.S. death records from 2003 to 2015 among decedents aged 25 or older, classified by racial or ethnic group. The researchers calculated annual percentage mortality rates, adjusting for age and sex, and stratified counties by median household income.

The researchers found that heart disease was the leading cause of death in 79% of counties in 2003, and that number had dropped to 59% by 2015. Meanwhile, cancer was the leading cause of death in 41% of counties in 2015, an increase from being the leading cause of death in 21% of counties in 2003. This shift to cancer as the leading cause of death was strongest in the highest-income counties.

The shift in leading cause of death from heart disease to cancer in the highest-income counties is due to a decrease in mortality rates. Overall, heart disease mortality rates in these counties decreased by 28% and cancer mortality rates decreased by 16% from 2003 to 2015.

But those improvements in mortality rates were smaller in the low-income counties, where heart disease mortality rates decreased by 22% and cancer mortality rates decreased by 11%. The study also found that in the counties where heart disease remained the leading cause of death, there was no difference in leading cause of death among racial and ethnic groups.

The researchers concluded that because lower-income counties have not experienced the same decrease in mortality rates as higher-income countries, those counties will be later to transition to cancer as the leading cause of death, which, if trends continue, will occur nationwide in 2020.