Health Inequalities Among Elderly Type 2 Diabetes Mellitus Patients in Japan

The influence of socioeconomic status (SES) on health inequalities has received much attention worldwide. This study examined the effect of SES on the following older type 2 diabetes mellitus patient health outcomes: oral hypoglycemic agent (OHA) medication adherence (proportion of days covered, PDC), risk of hospitalization for diabetic macrovascular complications, and in-hospital death. A retrospective cohort design using 2013-2016 claims data was used. Subjects were 58,349 diabetes patients aged >74 years in 2013. Age, sex, residential area, and comorbidities were controlled for. Logistic regression was conducted to assess the effects of income on PDC; survival analysis was used to assess the effects on hospitalization and in-hospital death. Regressions were conducted separately by sex. Compared with the lowest income group, adjusted PDC odds ratios for medium- and high-income males, respectively, were 1.35 (95% CI: 1.27-1.43) and 1.41 (95% CI: 1.30-1.54); females: 1.17 (95% CI: 1.11-1.23) and 1.24 (95% CI: 1.13-1.35). Adjusted hazard ratios (AHRs) for male hospitalization were 0.88 (95% CI: 0.80-0.96) and 0.88 (95% CI: 0.79-0.99); females: 1.00 (95% CI: 0.93-1.07) and 0.95 (95% CI: 0.83-1.08). AHRs for male in-hospital death were 0.83 (95% CI: 0.75-0.91) and 0.62 (95% CI: 0.54-0.70); females: 0.94 (95% CI: 0.87-1.02) and 0.77 (95% CI: 0.65-0.92). Results revealed sex-specific health inequalities among older Japanese diabetes patients. Subjects with worse SES had significantly poorer OHA medication adherence (both sexes), higher hospitalization risk for diabetes complications (males), and higher in-hospital death risk (both sexes).