County-level variation in cardiovascular disease mortality in the United States in 2009-2013: Comparative assessment of contributing factors

We examined factors responsible for variation in cardiovascular disease (CVD) mortality across US counties in 2009-2013. We linked county-level census, survey, administrative, and vital statistics data to examine 4 sets of features: demographic factors, social and economic factors, health-care utilization and features of the environment, and population health indicators. County-level associations of these features (standardized to a mean of 0 with a standard deviation of 1) with cardiovascular deaths per 100,000 person-years among adults aged 45-74 years was modeled using 2-level hierarchical linear regression with random intercept for state. The percentage of CVD mortality variation (intercounty disparity) modeled by each set of features was quantified. Demographic composition accounted for 36% of county CVD mortality variation, and another 32% was explained after inclusion of economic/social conditions. Health-care utilization, features of the environment, and health indicators explained an additional 6% of CVD mortality variation. The largest contributors to CVD mortality levels were median income (-23.61 deaths/100,000 person-years, 95% CI: -26.95, -20.26) and percentage without a high school education (20.71 deaths/100,000 person-years, 95% CI: 16.48, 24.94). In comparison, the largest health-related contributors were health-care utilization (19.35 deaths/100,000 person-years, 95% CI: 16.36, 22.34) and CVD risk factors (4.80 deaths/100,000 person-years, 95% CI: 2.14, 7.46). Improving healthcare access and decreasing the prevalence of traditional CVD risk factors may reduce county CVD mortality levels, but improving socioeconomic circumstances of disadvantaged counties will be required in order to reduce CVD mortality disparities across counties.