Systemic immune inflammation index with all-cause and cause-specific mortality: a meta-analysis

Studies have reported an association among systemic immune inflammation index (SII), all-cause and cause-specific mortality, but the results are inconsistent. To comprehensively explore the association between Systemic Immune Inflammation (SII) and the risk of all-cause mortality, cardiovascular disease (CVD), and cancer mortality. A meta-analysis was conducted by reviewing existing literature. The search encompassed prominent databases including PubMed, Embase, Cochrane, and the Web of Science, with the cutoff date set at March 1, 2024. Furthermore, subgroup analyses and dose-response assessments were undertaken to provide a nuanced exploration of mortality risk factors. A total of 33 articles were included (427,819 participants). In the study, SII was associated with an increased risk of all-cause mortality (HR = 1.45, 95%CI [1.36,1.54], P < 0.05). SII increased the risk of CVD mortality (HR = 1.44, 95%CI [1.29,1.60], P < 0.05). The Linear independence shows that for every 100 units increase in SII, the risk of all-cause and CVD death increases by 5% and 6%. SII was not associated with a statistically significant risk of cancer death (HR = 1.09, 95%CI [0.96,1.23], P < 0.05). Meta-analysis showed that SII was associated with all-cause mortality and CVD mortality. More data and basic research are needed to confirm the association.