Independent Impact of Diabetes on the Severity of Coronavirus Disease 2019 in 5,307 Patients in South Korea: A Nationwide Cohort Study

BACKGROUND: Inconsistent results have been observed regarding the independent effect of diabetes on the severity of coronavirus disease 2019 (COVID-19). We conducted a nationwide population-based cohort study to evaluate the relationship between diabetes and COVID-19 severity in South Korea. METHODS: Patients with laboratory-confirmed COVID-19 aged ≥30 years were enrolled and medical claims data were obtained from the Korean Health Insurance Review and Assessment Service. Hospitalization, oxygen treatment, ventilator application, and mortality were assessed as severity outcomes. Multivariate logistic regression analyses were performed after adjusting for age, sex, and comorbidities. RESULTS: Of 5,307 COVID-19 patients, the mean age was 56.0±14.4 years, 2,043 (38.5%) were male, and 770 (14.5%) had diabetes. The number of patients who were hospitalized, who received oxygen, who required ventilator support, and who died was 4,986 (94.0%), 884 (16.7%), 121 (2.3%), and 211 (4.0%), respectively. The proportion of patients with diabetes in the abovementioned outcome groups was 14.7%, 28.1%, 41.3%, 44.6%, showing an increasing trend according to outcome severity. In multivariate analyses, diabetes was associated with worse outcomes, with an adjusted odds ratio (aOR) of 1.349 (95% confidence interval [CI], 1.099 to 1.656; P=0.004) for oxygen treatment, an aOR of 1.930 (95% CI, 1.276 to 2.915; P<0.001) for ventilator use, and an aOR of 2.659 (95% CI, 1.896 to 3.729; P<0.001) for mortality. CONCLUSION: Diabetes was associated with worse clinical outcomes in Korean patients with COVID-19, independent of other comorbidities. Therefore, patients with diabetes and COVID-19 should be treated with caution.