Cardiometabolic Multimorbidity Increases the Risk of Hip Fracture: A Longitudinal Cohort Study Based on <scp>CHARLS</scp>

BACKGROUND: Cardiometabolic Multimorbidity (CMM) is defined as the co-occurrence of two or more conditions among heart disease, diabetes mellitus, stroke, and hypertension. Previous studies have shown associations between cardiometabolic diseases and fragility fractures; however, the relationship between CMM and hip fractures remains unclear in the Chinese population. This study therefore aims to investigate this association in a Chinese cohort to inform fracture prevention strategies. METHODS: This prospective cohort study used data from the China Health and Retirement Longitudinal Study (CHARLS) collected from 2011 to 2020. Participants from the 2011 baseline survey cohort were initially included. Subsequently, individuals were sequentially excluded if they were under 45 years of age, had incomplete baseline CMM information, had a history of hip fracture, lost to follow-up, or had missing data on confounders. Kaplan-Meier survival analysis, Cox proportional hazards regression, subgroup analyses, and sensitivity analyses were performed to evaluate the association between CMM and the risk of hip fracture. RESULTS: A total of 6314 participants aged 45 years and older were included, of whom 544 had CMM. Over a 9-year follow-up period, 287 incident hip fractures (4.55%) were identified. Among these, 36 participants had been diagnosed with CMM at baseline, whereas 251 had not. The incidence of hip fracture was significantly higher in participants with CMM than in those without CMM (13% vs. 8%, p = 0.015). After full adjustment for confounders, multivariable Cox regression showed that CMM was associated with a 70% increased risk of hip fracture (HR = 1.70, 95% CI: 1.318-2.47; p = 0.005). Subgroup analyses indicated that age and history of falls were significant effect modifiers. The association between CMM and hip fracture was more pronounced in participants under 60 years old (P for interaction = 0.048) and those with a history of falls (P for interaction = 0.014). CONCLUSION: These findings suggest that CMM increases the risk of hip fracture, particularly among relatively younger individuals and those with a history of falls.