Risk for Newly Diagnosed Type 2 Diabetes Mellitus after COVID-19 among Korean Adults: A Nationwide Matched Cohort Study

BACKGROUND: Coronavirus disease 2019 (COVID-19) can cause various extrapulmonary sequelae, including diabetes. However, it is unclear whether these effects persist 30 days after diagnosis. Hence, we investigated the incidence of newly diagnosed type 2 diabetes mellitus (T2DM) in the post-acute phase of COVID-19. METHODS: This cohort study used data from the Health Insurance Review and Assessment Service, a representative national healthcare database in Korea. We established a cohort of 348,180 individuals diagnosed with COVID-19 without a history of diabetes between January 2020 and September 2021. The control group consisted of sex- and age-matched individuals with neither a history of diabetes nor COVID-19. We assessed the hazard ratios (HR) of newly diagnosed T2DM patients with COVID-19 compared to controls, adjusted for age, sex, and the presence of hypertension and dyslipidemia. RESULTS: In the post-acute phase, patients with COVID-19 had an increased risk of newly diagnosed T2DM compared to those without COVID-19 (adjusted HR, 1.30; 95% confidence interval [CI], 1.27 to 1.33). The adjusted HRs of non-hospitalized, hospitalized, and intensive care unit-admitted patients were 1.14 (95% CI, 1.08 to 1.19), 1.34 (95% CI, 1.30 to 1.38), and 1.78 (95% CI, 1.59 to 1.99), respectively. The risk of T2DM in patients who were not administered glucocorticoids also increased (adjusted HR, 1.29; 95% CI, 1.25 to 1.32). CONCLUSION: COVID-19 may increase the risk of developing T2DM beyond the acute period. The higher the severity of COVID-19 in the acute phase, the higher the risk of newly diagnosed T2DM. Therefore, T2DM should be included as a component of managing long-term COVID-19.