Association of systemic immune-inflammatory index with all-cause mortality and cancer mortality in Americans aged 60 years and older

Wangfeng Lu ^* Yuliang Gong ^* Lei Liu ^* Yonghong Zhang ^* Xiaojian Tian ^*

• Shangluo Central Hospital, Shangluo, China

This study examined the association between systemic immune inflammatory index (SII) and all-cause mortality and cancer-related deaths among people aged 60 years and older in the United States, spanning 1999 -2018 with follow-up until 31 December 2019, using data from 4295 population-based participants in the National Health and Nutrition Examination Survey (NHANES). Cox proportional risk models, restricted cubic spline, survival curves and subgroup analyses were used to analyses the relationship between SII and mortality, respectively. The mean age of the participants was 70.7 (7.6) years, the median follow-up time was 131.7 (59.8) months, and the overall mortality rate was 50.5%. the results of the Cox regression model showed that SII remained significantly associated with all-cause mortality (HR = 1.31, 95% CI = 1.15 ~1.48) after adjusting for multiple variables. However, results for cancer mortality (HR = 1.23, 95% CI = 0.95-1.59) were less consistent. Restricted triple spline analysis showed a linear relationship between SII and all-cause mortality and a U-shaped relationship between SII and cancer death. The results of the survival curves indicated that the risk of all-cause mortality and cancer death was prognostically worse in patients when SII > 725.33 compared to the other groups.