Abstract
BACKGROUND: The Systemic Immune-Inflammation Index (SII) is widely studied for its role in evaluating Cardiovascular Disease (CVD) and mortality. However, its association with all-cause and CVD mortality in non-elderly diabetic adults remains unclear. This study aims to explore the relationship between SII and both all-cause and CVD mortality in non-elderly diabetic adults in the United States. METHODS: Cox proportional hazards models and subgroup analyses were used to assess the link between SII and mortality. Restricted Cubic Splines (RCS) examined the nonlinear association between SII and mortality. RESULTS: Data from 4680 participants in NHANES (2001‒2018) were analyzed. Over an average follow-up of 98.3 months, there were 625 all-cause deaths and 162 CVD-related deaths. Participants were categorized into two SII groups (higher: > 947.625, lower: ≤ 947.625). Multivariable-adjusted models showed that higher SII levels were significantly associated with an increased risk of both CVD mortality (HR = 3.05; 95 % CI 1.85, 5.01) and all-cause mortality (HR = 1.97; 95 % CI 1.50, 2.58). Subgroup analyses confirmed the consistency of these associations. RCS analysis revealed a nonlinear relationship between SII and all-cause mortality, while the association with CVD mortality was linear. CONCLUSION: Higher SII levels in non-elderly diabetic adults in the U.S. are linked to an increased risk of both CVD and all-cause mortality.