Abstract P180: Combined Effect of Income and Medication Adherence on Mortality in Newly Treated Hypertension: a Nationwide Study of 16 Million Person-years

Abstract

Introduction: Low socioeconomic status and poor medication adherence are known to increase mortality among patients with hypertension, but their combined effects have not been well studied. Hypothesis: We hypothesized that excess risks for all-cause and cardiovascular deaths by medication adherence are greater in lower income individuals with hypertension. Methods: We followed 1,679,527 persons, aged 30 to 80 years, with newly treated hypertension and no prior cardiovascular disease (CVD), for 10 years using the Korean National Health Insurance database. Exposure variables were household income in quintiles and medication adherence estimated by medication possession ratio: good (≥0.8), moderate (0.5 to <0.8), or poor (<0.5). Outcomes were all-cause and CVD-related deaths. We used Cox proportional hazards model to calculate hazard ratios (HR) adjusted for age, sex, comorbidity, and other covariates. Results: Both low income and poor adherence were independently associated with higher mortality (HR=1.51, 95% CI=1.49-1.54, lowest vs. highest income; HR=1.65, 95% CI=1.64-1.67, poor vs. good adherence). However, when stratified by combination of income and adherence (figure), excess risk by non-adherence gradually increased towards lower household income, especially in men. Excess risk for death by poor medication adherence was 117% (HR, 2.78 vs. 1.61, poor vs. good adherence) in lowest-income men and 59% in highest-income men. In women, risk difference by income was also present, but was not as prominent as in men. Excess risk for death by poor adherence was 75% (HR, 2.07 vs. 1.32, poor vs. good adherence) in lowest-income women and 54% in highest-income women. Similar findings were observed for CVD-related death also. Conclusion: Poor medication adherence is associated with higher mortality, but patients with low income are subject to greater excess risk by non-adherence. This highlights the potential importance of promoting adherence for risk reduction especially in low-income patients with hypertension.