Deciphering the Threshold and Segmented Nonlinear Association Between Systemic Inflammation Response Index and Spinal Bone Density: Insights From a Large-Scale Population Study.

Study DesignCross-sectional study.ObjectiveTo examine the association between SIRI and spinal BMD and assess the influence of age, hypertension, and diabetes.MethodsWe analyzed data from 13,950 participants aged ≥20 years. SIRI was calculated using neutrophil, monocyte, and lymphocyte counts, and spinal BMD was measured by DXA. Linear regression, generalized additive models, and segmented regression were used, with subgroup analyses based on age, hypertension, and diabetes.ResultsA threshold effect was observed at SIRI = 0.68. Below this threshold, SIRI negatively correlated with spinal BMD (β = -0.0412, = 0.0494), while above it, a positive correlation was found (β = 0.0079, < 0.0001). Subgroup analyses showed stronger positive associations in older adults (≥65 years, β = 0.0136, < 0.0001), and those with hypertension (β = 0.0089, = 0.0004) and diabetes (β = 0.0187, < 0.001).ConclusionA segmented nonlinear relationship exists between SIRI and spinal BMD, with age, hypertension, and diabetes as significant modifiers. SIRI may serve as a biomarker for osteoporosis risk.