The association between hemoglobin at admission and mortality of older patients with hip fracture: a mean 3-year follow-up cohort study.

ABSTRACT

BACKGROUND: Hip fracture patients often have a large drop in hemoglobin (Hgb) concentration that is associated with the initial trauma. However, there is no study of a correlation between Hgb concentration at admission and short-term mortality. Thus, we evaluated a possible linear and nonlinear association between Hgb and mortalityfor older patients with hip fracture. METHODS: Consecutive older patients who had hip fractures were screened between January 2015 and September 2019. Demographic and clinical characteristics were collected. Linear and nonlinear multivariate Cox regression models were used to identify association between Hgb at admission and mortality. All analyses were performed with EmpowerStats and R software. RESULTS: Two thousand five hundred eighty-nine patients were included in the study. There were 849 men and 1740 women. The mean age was 79.6 ± 6.8 years. The mean follow-up was 39.0 months. Nine hundred seven (35.0%) patients died for all-cause reasons. The mean Hgb at admission was 11.07 ± 1.95 g/dL. Linear multivariate Cox regression models showed Hgb at admission was associated with mortality ([Hazard Ratio] HR 0.91, 95% CI 0.87-0.95, P < 0.0001) after adjusting for confounding factors. However, the linear association was unstable, and nonlinearity was found between Hgb at admission and mortality. The Hgb concentration of 9.8 g/dL was an inflection point. A Hgb at admission < 9.8 g/dL was associated with mortality (HR 0.81, 95% CI 0.74-0.89, P < 0.0001), whereas > 9.8 g/dL was not a risk factor for mortality (HR 0.98, 95% CI 0.92-1.04, P = 0.4730). CONCLUSIONS: The Hgb concentration at admission was nonlinearly associated with mortality of older patients with hip fracture, and Hgb at admission < 9.8 g/dL was a risk predictor of 3-year mortality. RESEARCH REGISTRATION ChiCTR2200057323.