Is inequality at the heart of it? Cross-country associations of income inequality with cardiovascular diseases and risk factors

Abstract

Despite a number of cross-national studies that have examined the associations between income inequality and broad health outcomes such as life expectancy and all-cause mortality, investigations of the cross-country relations between income inequality and cardiovascular disease (CVD) morbidity, mortality, and risk factors are sparse. We analyzed the cross-national relations between income inequality and age-standardized mean body mass index (BMI), serum total cholesterol, systolic blood pressure (SBP), obesity prevalence, smoking impact ratio (SIR), and age-standardized and age-specific disability-adjusted life-years (DALYs) and mortality rates from coronary heart disease (CHD) and stroke, controlling for multiple country-level factors and specifying 5- to 10-year lag periods. In multivariable analyses primarily limited to industrialized countries, countries in the middle and highest (vs. lowest) tertiles of income inequality had higher absolute age-standardized obesity prevalences in both sexes. Higher income inequality was also related to higher mean SBP in both sexes, and higher SIR in women. In analyses of larger sets of countries with available data, positive associations were observed between higher income inequality and mean BMI, obesity prevalence, and CHD DALYs and mortality rates. Associations with stroke outcomes were inverse, yet became positive with the inclusion of eastern bloc and other countries in recent economic/political transition. China was also identified to be an influential data point, with the positive associations with stroke mortality rates becoming attenuated with its inclusion. Overall, our findings are compatible with harmful effects of income inequality at the national scale on CVD morbidity, mortality, and selected risk factors, particularly BMI/obesity. Future studies should consider income inequality as an independent contributor to variations in CVD burden globally.