股関節骨折患者におけるビタミンD欠乏症の有病率、予測因子、および12ヶ月後の転帰への臨床的影響

PURPOSE: Vitamin D deficiency (VDD) is common in older adults with osteoporosis, but its prevalence, determinants, and clinical impact in hip fracture (HF) patients remain incompletely defined. This study investigated the prevalence of VDD, associated factors, and 12-month outcomes in HF patients managed within a Fracture Liaison Service program. METHODS: In this prospective cohort study, 934 patients hospitalized for HF were enrolled between March 2023 and March 2025. VDD was defined as serum 25-hydroxyvitamin D [25-(OH)D] < 50 nmol/L. Clinical characteristics, laboratory parameters, and 12-month outcomes were assessed. RESULTS: Overall VDD prevalence was 53.6%, with a median 25-(OH)D concentration of 22 nmol/L among deficient patients. Independent predictors of VDD were male sex (p < 0.001), diabetes mellitus (p = 0.003), dementia (p = 0.013), and active smoking (p = 0.045), while prior vitamin D supplementation was negatively associated (p < 0.001). Decision tree analysis showed VDD prevalence ranging from 17.2% to 86.3% across patient phenotypes. Patients with VDD showed higher levels of bone turnover markers. In unadjusted analyses, VDD was associated with higher 12-month mortality (HR 1.65, 95% CI 1.12-2.42, p = 0.010), an association attenuated and no longer significant after adjustment for age, sex, and comorbidity burden (HR 1.31, 95% CI 0.88-1.96, p = 0.188). No associations were observed between VDD and rehospitalization or refracture rates. CONCLUSION: VDD is highly prevalent in HF patients. Although associated with higher mortality in unadjusted analyses, this relationship appears largely explained by comorbidity burden. These findings highlight the importance of recognizing VDD and implementing targeted vitamin D supplementation strategies in high-risk HF populations.