Sex differences in hemoglobin levels and five-year refracture risk in patients with osteoporotic fractures: a retrospective cohort analysis

We conducted a retrospective cohort analysis to examine the association between hemoglobin (Hb) levels and refracture risk in elderly patients with osteoporotic fractures (OPFs). Our findings suggest a nonlinear relationship exists in females, and females with Hb levels below 10.7 g/dL may be at a higher risk of refracture. Introduction Hematopoiesis and bone health have a reciprocal influence on each other. Nevertheless, there is a scarcity of in-depth research on the association between Hb levels and the occurrence of fractures. The present research aimed to investigate the correlation between Hb levels and the rate of refracture within 5 years among individuals with OPFs. Methods A retrospective cohort analysis was undertaken between 2017 and 2022. The study included 1906 individuals who were inhabitants of Kunshan and were over 60 years old. These individuals had experienced an OPF between January 1, 2017, and July 27, 2022, resulting in their hospitalization. Cox proportional hazard regression models were used to evaluate the risk of refracture within 5 years based on the Hb levels acquired during the admission examination, with consideration for sex differences. A nonlinear relationship was identified using smoothed curve fitting and threshold analysis. Kaplan-Meier curves were used to compare refracture rates between patients with low and high Hb levels. Results Elderly female patients with OPFs and lower Hb levels exhibited a significantly higher risk of a 5-year refracture. Conversely, no significant associations were observed between the two variables in male patients. A nonlinear correlation was found between Hb levels and the probability of refracture in females, with a turning point identified at 10.7 g/dL of Hb levels. A strong negative association was observed with the five-year refracture rate when Hb levels fell below 10.7 g/dL (hazard ratio (HR) = 0.63; 95% confidence interval (CI) 0.48 to 0.83; P-value = 0.0008). This finding suggests that for every 1 g/dL increase in Hb below 10.7 g/dL, the risk of refracture reduced by 37%. However, no statistically significant association was observed when Hb levels were above 10.7 g/dL. Conclusions The findings demonstrated a significant negative correlation between Hb levels and the likelihood of refracture in elderly female patients with OPFs and suggested that elderly females with recent OPFs and Hb levels below 10.7 g/dL may be at a higher risk of refracture. Additionally, the Hb levels can serve as an indicator of bone fragility in elderly female patients with OPFs. These findings highlight the importance of monitoring Hb levels as a part of comprehensive management strategies to both assess skeletal health and prevent refractures in this population.