Association between systemic immune-inflammation index and mortality in patients receiving maintenance hemodialysis: a retrospective cohort study

Chronic inflammation is common in patients receiving maintenance hemodialysis (MHD) and is closely related to adverse clinical outcomes. The clinical significance of the systemic immune-inflammation index (SII), a composite marker derived from routine blood cell counts, has not been fully characterized in dialysis populations. This retrospective cohort study included 408 MHD patients with a median follow-up of 33 months. SII was calculated from baseline platelet, neutrophil, and lymphocyte counts. Associations between SII and all-cause and cardiovascular mortality were evaluated using multivariable Cox proportional hazards models. Restricted cubic spline analyses were performed to assess dose–response relationships. Kaplan–Meier analyses and subgroup analyses were conducted to explore the consistency of associations. During follow-up, 91 patients died, including 39 cardiovascular deaths. Higher SII levels were associated with increased risks of both all-cause mortality (HR 1.89, 95% CI 1.29–2.77) and cardiovascular mortality (HR 2.08, 95% CI 1.21–3.57). Patients in the highest SII tertile had approximately two-fold higher risk of all-cause mortality compared with those in the lowest tertile. Kaplan–Meier analyses demonstrated significantly lower survival probabilities among patients with higher SII levels. Subgroup analyses showed generally consistent associations across most clinically relevant strata. Higher SII levels were associated with increased risks of all-cause and cardiovascular mortality in patients receiving maintenance hemodialysis. These findings suggest that SII, derived from routine blood cell counts, may reflect inflammatory processes linked to adverse outcomes in dialysis populations. Not applicable.