Association of serum urea-to-creatinine and creatinine-to-cystatin C ratios with bone mineral density and osteoporosis: a cross-sectional study

Sarcopenia and osteoporosis are two closely related degenerative diseases, and the urea-to-creatinine ratio (UCR) and creatinine-to-cystatin C ratio (CCR) have been reported as recognized muscle markers. Therefore, this study aims to investigate the relationship between muscle indicators (UCR and CCR) and bone mineral density (BMD), and osteoporosis prevalence. This cross-sectional study included 1,146 participants, of whom 363 were diagnosed with osteoporosis. Through regression and smooth curve fitting analysis, after adjusting for covariates, it was revealed that UCR was positively correlated with the risk of osteoporosis (OR = 1.020, 95% CI 1.011-1.029), and negatively correlated with BMD of lumbar spine (β = - 0.002, 95% CI - 0.002 to - 0.001), total hip (β = - 0.001, 95% CI - 0.002 to - 0.001), and femoral neck (β = - 0.001, 95% CI - 0.002 to - 0.001) (all P < 0.001). In contrast, CCR was negatively correlated with the prevalence of osteoporosis (OR = 0.839, 95% CI 0.762-0.923) and positively correlated with BMD at the lumbar spine (β = 0.016, 95% CI 0.010-0.022), total hip (β = 0.014, 95% CI 0.009-0.019), and femoral neck (β = 0.012, 95% CI 0.008-0.017) (all P < 0.001). In subgroup analyses, muscle markers were significantly associated with osteoporosis in women, normal-weight, and overweight patients. After categorizing UCR and CCR according to quartiles, their associations with osteoporosis risk and BMD remained significant. These results helped to understand the correlation between muscle markers (UCR and CCR) and BMD, providing new ideas for the evaluation and screening of osteoporosis.