Renal function and rate of hip bone loss in older men: The Osteoporotic Fractures in Men Study

Summary: Older men with reduced renal function are at increased risk of hip bone loss. Given the robustness of this association across different measures and a growing body of literature, our findings indicate that clinicians should take into account renal function when evaluating older men for osteoporosis risk and bone loss. Future randomized controlled trials should test whether interventions in this high risk population are effective in preventing bone loss and decreasing fracture incidence. Introduction: Studies examining whether kidney impairment, not requiring dialysis, is associated with osteoporosis have reported conflicting results. Methods: We tested the hypothesis that reduced renal function in older men as manifested by higher concentrations of cystatin C or lower levels of estimated glomerular filtration rate (eGFR) is associated with higher rates of bone loss. We measured serum cystatin C, serum creatinine and total hip bone mineral density (BMD) at baseline in a cohort of 404 older men enrolled in the Osteoporotic Fractures in Men (MrOS) Study and followed them prospectively for an average of 4.4 years for changes in BMD. Associations between renal function and change in hip BMD were examined using linear regression. Results: In multivariable analysis, the mean rate of decline in total hip BMD showed an increase in magnitude with higher cystatin C concentration (mean annualized percent change -0.29, -0.34, -0.37 and -0.65% for quartiles 1 to 4; p for trend=0.004). Similarly, adjusted rates of hip bone loss were higher among men with lower eGFR as defined by the modification of diet in renal disease formula (mean annualized percent change -0.58, -0.39, -0.37, and -0.31 for quartiles 1 to 4; p for trend=0.02), but not among men with lower eGFR as defined by the Cockcroft-Gault formula (mean annualized percent change -0.47, -0.44, -0.31 and -0.43 for quartiles 1 to 4; p for trend=0.48). Conclusions: Older men with reduced renal function are at increased risk of hip bone loss. Our findings suggest that health care providers should consider renal function when evaluating older men for risk factors for bone loss and osteoporosis.