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 consecu-tive 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.