Income level and inequality as complement to geographical differences in cardiovascular trials

Abstract

Background: Analyses of country or regional differences in cardiovascular (CV) trials are based on geographical subgroup analyses. However, apart from map location and related racial, ethnic, and genetic variations, identified differences may also depend on social structure and provision and access to health care, for which country income and income inequality are indicators. The aim of the study was to examine the association between country per capita income and income inequality and prognosis in patients with heart failure or an acute coronary syndrome in 3 international trials (EMPHASIS-HF, EPHESUS, and EXAMINE).

Methods: Countries were classified into high income or low-middle income (LMICs) and into low, middle, or high inequality using the Gini index. The main outcome measures were all-cause and CV death.

Results: Patients from LMICs and countries with higher inequality were younger, were less often white, had fewer comorbid conditions, and were less often treated with guideline-recommended therapies, including devices. These patients had higher adjusted mortality rates (+15% to +70%) compared with patients from high-income countries and countries with less inequality. Patients from countries with the combination of greater inequality and low-middle income had particularly high mortality rates (+80% to +190%) compared with those that did not have both characteristics. Living in a country that is poor and has inequality had more impact on death rates than any comorbidity. These findings were reproduced in 3 trials.

Conclusions: Patients from LMICs and countries with greater inequality had the highest mortality rates. The prognostic impact of income and inequality is substantial and should be considered when looking into subgroup differences in CV trials.