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.