Systemic immune-inflammation index and 2-year all-cause mortality in elderly patients with hip fracture

Purpose: To assess the association between systemic immune-inflammation index (SII) and 2-year all-cause mortality in elderly patients with hip fractures. Methods: We performed a cohort study of hip fracture patients aged 65 years or older who received hip fracture surgery at a tertiary hospital from January 2005 to March 2022. The SII was calculated as: SII = (neutrophil count * platelet count) / lymphocyte count, based on the latest blood test before discharge. Patients were categorized into 3 groups according to SII tertiles: low SII group (<= 770.92 x 10(9)/L), medium SII group (770.92 x 10(9)/L -1293.03 x 10(9)/L), and high SII group (>1293.03 x 10(9)/L). The primary outcome was 2-year all-cause mortality. We evaluated the association between SII and 2-year all-cause mortality using the multivariate Cox regression model. Results: Among 2766 patients, 296 patients died during the 2-year follow-up period. The incidence of 2-year all-cause mortality per 1000 persons was 90.0 (95 % CI: 73.2-110.2) in the low SII group, 86.8 (95 % CI: 70.3-106.7) in the medium SII group, and 144.3 (95 % CI: 123.1-168.5) in the high SII group. Compared with patients in the low SII group, the hazard ratio for 2-year all-cause mortality was 0.97 (95 % CI: 0.69-1.37) in the medium SII group and 1.47 (95 % CI: 1.07-2.01) in the high SII group (P for trend, 0.010). Conclusion: SII is significantly associated with 2-year all-cause mortality in elderly patients with hip fracture. SII may be used to identify patients at high risk of mortality after hip fracture surgery.