Impact of systemic immune-inflammation index and systemic inflammation response index on all-cause and cause-specific mortality: a community-based cohort study.

Objective: To examine the associations of the systemic immune-inflammation index (SII) and systemic inflammation response index (SIRI) with mortality in a Chinese community-based population. Methods: We analyzed data from 9,318 participants in a community-based prospective cohort Study in Pudong New Area, Shanghai, China. Associations between SII/SIRI and mortality were evaluated using Cox and Fine-Gray models. Non-linear relationships were examined using restricted cubic splines. Stratified analyses and measures of model discrimination and reclassification were also performed. Results: After multivariable adjustment, the highest SII quartile (Q4) was associated with higher risks of all-cause mortality (HR = 1.35, 95% CI: 1.14-1.61), cardiovascular mortality (HR = 1.33, 95% CI: 1.02-1.73), and respiratory mortality (HR = 3.37, 95% CI: 1.44-7.90), but not cancer mortality. For SIRI, Q4 was associated with higher risks of all-cause mortality (HR = 1.68, 95% CI: 1.39-2.04), cardiovascular mortality (HR = 1.40, 95% CI: 1.05-1.87), cancer mortality (HR = 1.45, 95% CI: 1.02-2.05), and respiratory mortality (HR = 3.07, 95% CI: 1.34-7.02). Significant dose-response relationships were observed for both SII and SIRI with all-cause and cause-specific mortality. Subgroup analysis indicated stronger associations of SIRI with all-cause mortality in participants aged < 60 years. Adding SIRI or SII to conventional risk models improved predictive performance for mortality, with SIRI providing more consistent enhancement across outcomes. Conclusions: Our findings identify SII and SIRI as independent risk factors for mortality, with SIRI demonstrates superior prognostic value for both all-cause and cause-specific mortality.