The U-shaped correlation between the systemic immune-inflammation index and all-cause and cardiovascular mortality in hyperlipidemic patients: findings from NHANES 1999–2018

BACKGROUND: The relationship of systemic immune-inflammation index (SII) with mortality in hyperlipidemic patients remains unknown. In the present work, we evaluated SII for its ability to predict mortality incidence and examined its relationship with mortality of hyperlipidemic individuals. METHODS: Altogether 27,903 hyperlipidemic cases were collected during 1999-2018 following the National Health and Nutrition Examination Survey (NHANES). SII was determined with complete blood count parameters. Our main results included all-cause and cardiovascular disease (CVD) mortality. We conducted Kaplan-Meier survival, restricted cubic spline (RCS), and Cox proportional hazards model analyses to assess the connection of SII to mortality among hyperlipidemic patients. To ensure that these results were reliable, we also conducted sensitivity and subgroup analyses. RESULTS: < 0.0001) of hyperlipidemic individuals. According to our threshold analysis results, thresholds for lnSII were 6.08 and 5.96. Subgroup and sensitivity analyses yielded reliable results. CONCLUSIONS: For representative hyperlipidemic patients, SII shows the non-linear, U-shaped relationship with all-cause and CVD mortality.