Background: Persons with end-stage renal disease are at higher risk for osteopenia and hip fracture relative to the age-matched general population. Persons with mild to moderate chronic renal insufficiency (CRI) may have reduced bone mineral density (BMD) as a result of abnormalities in acid-base and vitamin D-parathyroid hormone homeostasis.
Methods: We analyzed data on 13,848 adults aged 20 and above from the Third National Health and Nutrition Examination Survey (NHANES III; 1988-1994). Regression models were used to determine the relationship between femoral BMD and renal function, the latter assessed using serum creatinine, blood urea nitrogen or Cockcroft-Gault creatinine clearance. To control for confounding, we fit sex-stratified models that adjusted for age, weight, height, race-ethnicity, menopausal status, estrogen use, activity level, family history of osteoporosis, diuretic use, and dietary intake of calcium and alcohol.
Results: Although subjects with reduced renal function had significantly lower femoral BMD in unadjusted analysis, the association between CRI and bone mineral density was extinguished after adjustment in the multivariate models. In fact, controlling for only sex, age and weight was sufficient to extinguish any negative association between decreased renal function and decreased bone mineral density.
Conclusion: Although subjects with worse renal function have significantly lower femoral BMD, this association can be explained by confounding, principally by sex, age and weight. After taking into account the facts that women, older individuals and smaller individuals have less renal function and lower BMD, renal function itself is not independently associated with BMD.