The interaction between type 2 diabetes and chronic kidney disease worsens the outcomes of patients with COVID-19: a retrospective study

Background: Type 2 diabetes and chronic kidney disease (CKD) have been reported to be associated with COVID-19, but the effect of an interaction between the two on the outcomes of COVID-19 has not been defined. Therefore, we aimed to investigate the effect of their interaction on COVID-19 outcomes. Methods The data of this retrospective study was from the multicenter study with COVID-19, type 2 diabetes, CKD and confounding factors information. Multivariate logistic regression model and subgroup analyses of different worse outcomes were conducted to assess the relationship between type 2 diabetes and CKD on worse outcomes in patients with COVID-19. Relative excess risk due to interaction (RERI), attributable proportion of interaction (AP) and synergy index (S) were utilized to assess the additive interaction. Results We found that patients with COVID-19 alongside type 2 diabetes or CKD were more likely to experience poor outcomes. Moreover, there was a significant interaction between type 2 diabetes and CKD regarding the risk of a poor outcome [RERI 20.134 (95% confidence interval (CI) 12.256–60.093), AP 0.742 (95% CI 0.538–0.945), SI 4.353 (95% CI 1.843–10.277)]. A subgroup analysis of the various adverse outcomes showed that the combination had a synergistic effect on in-hospital mortality. Conclusions Thus, type 2 diabetes and CKD increase the risk of a poor outcome in patients with COVID-19, and they interact synergistically to induce worse outcomes, especially in-hospital mortality.