Association of systemic immune-inflammatory index with all-cause and cardiovascular mortality among individuals with diabetes: Evidence from the NHANES 2001 to 2018

Evidence regarding the systemic immune-inflammatory index (SII) and mortality in patients with diabetes is limited. This study aimed to investigate the relationship of the SII with all-cause and cardiovascular mortality in patients with diabetes. Adults with diabetes from the National Health and Nutrition Examination Survey (NHANES) 2001 to 2018 were enrolled in our study. Weighted multivariable Cox regression models were used to investigate the association between SII and mortality from all causes and cardiovascular disease. Subgroup analyses, sensitivity analyses, restricted cubic spline (RCS) and Kaplan-Meier methods were also used. This study included 6620 patients in total. After multivariate adjustment, Cox proportional hazards regression models showed that participants in the quartile 4 (Q4) group had a significantly higher risk of both all-cause mortality (hazard ratio [HR], 1.43; 95% confidence interval [CI]: 1.16-1.77) and cardiovascular mortality (HR, 1.70; 95% CI: 1.04-2.77) compared with participants in the Q1 group. RCS analysis showed that there were nonlinear associations of SII with all-cause mortality (P < .001 for nonlinearity) and cardiovascular mortality (P = .001 for nonlinearity) among patients with diabetes. In addition, the survival rate of all-cause death differed across the 4 groups, with the survival rate of Q4 group significantly shortest during follow-up (weighted log-rank P < .001). This study indicated that an elevated SII was significantly associated with an increased risk of all-cause and cardiovascular mortality among individuals with diabetes.