Diabetes, Hypertension, and Incidence of Chronic Kidney Disease: Is There any Multiplicative or Additive Interaction?

Background The burden of chronic kidney disease (CKD) is on the rise worldwide; diabetes and hypertension are mentioned as the main contributors. Objectives The current study aimed to investigate the multiplicative and additive interaction of diabetes and hypertension in the incidence of CKD. Methods In this population-based cohort study, 7342 subjects aged 20 years or above (46.8% male) were divided into four groups: no diabetes and hypertension; diabetes and no hypertension; hypertension and no diabetes; and both diabetes and hypertension. The multivariable Cox regression was used to determine the effect of diabetes, hypertension, and their multiplicative interaction on CKD. The following indices were used to determine the additive interaction of diabetes and hypertension: the relative excess risk of interaction, the attributable proportion due to interaction, and the synergism index. Results Diabetes and hypertension had no significant multiplicative interaction in men (hazard ratio of 0.93, P value: 0.764) and women (hazard ratio of 0.79, P value: 0.198); furthermore, no additive interaction was found in men (relative excess risk due to interaction of 0.79, P value: 0.199; attributable proportion due to interaction of 0.22, P value: 0.130; synergy index of 1.44, P value: 0.183) and women (relative excess risk due to interaction of -0.26, P value: 0.233, attributable proportion due to interaction of -0.21, P value: 0.266; synergy index of 0.48, P value: 0.254). Conclusions This study demonstrated no synergic effect between diabetes and hypertension on the incidence of CKD.