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

Abstract

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 through dual-energy x-ray absorptiometry through the Korean National Screening Program between 2010 and 2016. BMD was categorized as normal, osteopenia, and osteoporosis on the basis of T-score. Kidney function was classified as eGFR >= 60, 45-59, and <45 ml/min per 1.73 m(2). Primary outcome was any fracture, including vertebral, hip, and other fractures, defined using International Classification of Diseases, Tenth Revision codes. Subgroup analysis was performed by physical performance, including the single leg stance test. Results Among 551,548 participants included in the main study population, 80,514 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 nonsignificant interaction (P for interaction = 0.54). Among participants with normal BMD, those with eGFR <45 ml/min per 1.73 m(2) showed a greater risk of hip fracture than those with normal eGFR (adjusted hazard ratio, 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 single leg stance 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.