Disparities in socioeconomic status and neighborhood characteristics affect all-cause mortality in patients with newly diagnosed hypertension in Korea: a nationwide cohort study, 2002-2013

Background: Previous studies have shown that contextual factors and individual socioeconomic status (SES) were associated with mortality in Western developed countries. In Korea, there are few empirical studies that have evaluated the association between SES and health outcomes. Methods: We conducted cohort study to investigate the socioeconomic disparity in all-cause mortality for patients newly diagnosed with hypertension in the setting of universal health care coverage. We used stratified random sample of Korean National Health Insurance enrollees (2002-2013). We included patients newly diagnosed with hypertension (n = 28,306) from 2003-2006, who received oral medication to control their hypertension. We generated a frailty model using Cox's proportional hazard regression to assess risk factors for mortality. Results: A total of 7,825 (27.6%) of the 28,306 eligible subjects died during the study period. Compared to high income patients from advantaged neighborhoods, the adjusted hazard ratio (HR) for high income patients from disadvantaged neighborhoods was 1.10 (95% CI, 1.00-1.20; p-value = 0.05). The adjusted HR for middle income patients who lived in advantaged versus disadvantaged neighborhoods was 1.17 (95% CI, 1.08-1.26) and 1.27 (95% CI, 1.17-1.38), respectively. For low income patients, the adjusted HR for patients who lived in disadvantaged neighborhoods was higher than those who lived in advantaged neighborhoods (HR, 1.35; 95% CI, 1.22-1.49 vs HR, 1.28; 95% CI, 1.16-1.41). Conclusions: Neighborhood deprivation can exacerbate the influence of individual SES on all-cause mortality among patients with newly diagnosed hypertension.