Association Between Educational Status and Mortality According to Diabetes Status Among US Adults

OBJECTIVE: To examine differences in the association between educational attainment and mortality by the presence of diabetes and diabetic retinopathy (DR)—a major complication of diabetes. PATIENTS AND METHODS: We used a nationally representative sample of 54,924 US adults aged 20 years or older with diabetes from the National Health and Nutrition Examination Survey 1999-2018 and its mortality data through 2019. We applied the multivariable Cox proportional hazard models to investigate the associations between educational attainment (low, less than high school; middle, high school; and high, more than high school) and all-cause mortality according to diabetes status: nondiabetes, diabetes without DR, and diabetes with DR. Differences in the survival rate by educational attainment were evaluated using the slope inequality index (SII). RESULTS: Among the 54,924 participants (mean age, 49.9 years), adults in the low educational group reported an increased risk of all-cause mortality compared with those of the high educational group in any diabetes status (nondiabetes—hazard ratio [HR], 1.69; 95% CI, 1.56-1.82; diabetes without DR—HR, 1.61; 95% CI, 1.37-1.90; diabetes with DR—HR, 1.43; 95% CI, 1.10-1.86). SIIs among the diabetes without DR group and diabetes with DR group were 22.17 and 20.87 per 1000 person-years, respectively, which were 2 times greater than those among the nondiabetes group (SII=9.94). CONCLUSION: The differences in the mortality risks owing to the educational attainment increased by the presence of diabetes regardless of the complication of DR. Our findings indicate that prevention of diabetes itself is critical to mitigate health disparities by socioeconomic status such as education status.