Bone Mineral Density and the Risk of Fracture according to eGFR in Postmenopausal Women

Background: Although both lower bone mineral density (BMD) and impaired kidney function are well-established risk factors for fracture, large-scale studies evaluating their effects and interaction on fracture, particularly site-specific fractures including vertebra and hip, are still limited. Methods: The main study population included female participants aged 66 years who underwent BMD assessment via dual-energy X-ray absorptiometry through the Korean national screening program between 2010 and 2016. BMD was categorized as normal, osteopenia, and osteoporosis, based on T-score. Kidney function was classified as estimated glomerular filtration rate (eGFR) ≥60, 45–59, and <45 ml/min/1.73 m 2 . Primary outcome was any fracture, including vertebral, hip, and other fractures, defined using ICD-10 codes. Subgroup analysis was performed by physical performance, including the single leg stance (SLS) test. Results: Among 551,548 participants included in the main study population, 80514 developed any fracture over a median follow-up of 8.2 (interquartile range, 6.7–10.0) years. The prevalence of osteoporosis was 36%, and those with lower BMD showed higher eGFR and lower body mass index. Lower BMD was associated with a higher risk of any fracture, irrespective of eGFR, with non-significant interaction (p for interaction = 0.80). Among participants with normal BMD, those with eGFR <45 ml/min/1.73 m 2 showed a greater risk of hip fracture than those with normal eGFR (adjusted hazard ratio [aHR], 2.44 [1.88–3.18]), whereas vertebral fracture risks were similar across different eGFR categories at a given BMD status. Furthermore, a higher fracture risk with lower eGFR was more pronounced in women with poor static balance assessed by the SLS test than in those with normal static balance. Conclusions: In postmenopausal women, lower BMD was associated with a higher fracture risk, irrespective of eGFR. However, at any given BMD, lower eGFR was associated with a greater risk for hip fracture, but not for vertebral fracture.