OBJECTIVE: To assess whether diabetes mellitus (DM) or obesity are independent risk factors for severe COVID-19 outcomes and explore if the risk conferred by one condition is modified by the other.

METHODS: This retrospective cohort study of inpatient adults with COVID-19 used multivariable Cox regression to determine the independent effects of DM and obesity on the composite outcome of intubation, intensive care unit admission, or in-hospital mortality. Effect modification between DM and obesity was assessed with a statistical interaction term and exploration of stratum-specific effects.

RESULTS: Among 3533 patients, 1134 (32%) had DM, 1256 (36%) had obesity, and 430 (12%) had both. Diabetes and obesity were independently associated with the composite outcome (HR 1.14 [95% CI 1.01, 1.30] and HR 1.22 [1.05, 1.43], respectively). A statistical trend for potential interaction between DM and obesity was observed (p=0.20). Stratified analyses showed potential increased risk with obesity compared to normal body mass index among DM (HR 1.34 [1.04, 1.74]) and non-DM patients (HR 1.18 [0.96, 1.43]).

CONCLUSION: Diabetes and obesity are independent risk factors associated with COVID-19 severity. Stratified analyses suggest obesity may confer greater risk to patients with DM compared to patients without DM, and this relationship requires further exploration.