Sustained Low Income, Income Changes, and Risk of All-Cause Mortality in Individuals With Type 2 Diabetes: A Nationwide Population-Based Cohort Study

Abstract

OBJECTIVE There is limited evidence on the association of sustained low-income status, income changes, and all-cause mortality risk in individuals with type 2 diabetes (T2D). RESEARCH DESIGN AND METHODS Using the Korean Health Insurance Service database, we studied 1,923,854 adults with T2D (aged ≥30 years) without cardiovascular disease and cancer, who were enrolled from 2009 through 2012 and followed to the end of 2020 (median 10.8 years of follow-up). We defined income levels based on the amount of health insurance premiums and categorized them into quartiles, the first being the low-income group, and assessed the income status annually in the preceding 5 years. Cox proportional hazards models were used to quantify the association of low-income status and income changes with mortality, with adjustment for sociodemographic factors, comorbidities, and diabetes duration and treatment. RESULTS Participants who consecutively had low income showed a higher risk of mortality (hazard ratio [HR] 1.19; 95% CI 1.16–1.22), compared with those who had never been in the low-income group. This association was much stronger for consecutive recipients of Medical Aid, reflecting very-low-income status (HR 2.26; 95% CI 2.16–2.36), compared with those who had never been Medical Aid beneficiaries. Sustained low- and very-low-income status was associated with increased risk of mortality, specifically for younger adults (aged <40 years) and males. Those who experienced declines in income between the first (preceding 5 years) and the last (baseline) time points had an increased risk of mortality, regardless of baseline income status. CONCLUSIONS Among Korean adults with T2D, sustained low-income status and declines in income were associated with increased risk of mortality.