Systemic immune-inflammation index and mortality among individuals with circadian syndrome

Objective Evidence on the impact of the systemic immune-inflammation index on mortality risk among individuals with circadian syndrome is scarce. This study aimed to examine the association of the systemic immune-inflammation index with all-cause mortality, cardiovascular disease mortality, and cancer mortality among individuals with circadian syndrome. Methods We included adult participants with complete information on systemic immune-inflammation index and circadian syndrome from the National Health and Nutritional Examination Survey 2005–2018. Weighted Cox proportional hazards models and restricted cubic splines were used to estimate hazard ratios and 95% confidence intervals for all-cause, cardiovascular disease, and cancer mortality. Results This cohort study included 6010 participants in the analysis (mean (SD) age, 57.97 (15.40) years; 3132 participants aged ≥60 years; 2804 men). Over a median follow-up of 8.25 years, 1280 deaths were recorded, comprising 366 deaths from cardiovascular disease and 278 from cancer. Elevated systemic immune-inflammation index levels were strongly predictive of increased mortality risk relative to lower levels, with the multivariable-adjusted hazard ratios of 1.46 (95% confidence interval: 1.17–1.82) for all-cause mortality (p for trend < 0.001), 2.23 (95% confidence interval: 1.56–3.18) for cardiovascular disease mortality (p for trend < 0.001), and 1.03 (95% confidence interval: 0.70–1.50) for cancer mortality (p for trend = 0.791). We revealed evident nonlinear associations between the natural logarithm of systemic immune-inflammation index and all-cause (p < 0.001), cardiovascular disease (p = 0.009), and cancer (p < 0.001) mortality. Conclusion We demonstrated that higher systemic immune-inflammation index levels may be associated with an increased risk of all-cause and cardiovascular disease mortality among individuals with circadian syndrome. There was no evident association between systemic immune-inflammation index and the risk of cancer mortality.