Urinary cadmium and osteoporosis in U.S. women ≥ 50 years of age: NHANES 1988-1994 and 1999-2004

Background: Urinary cadmium (U-Cd) has been associated with decreased peripheral bone mineral density (BMD) and osteoporosis. This association, however, has not been confirmed using femoral BMD, the international standard for diagnosing osteoporosis, at levels < 1.0 μg Cd/g creatinine. Objectives: Our goal was to investigate the statistical association between U-Cd, at levels ≤ 1 μg/g creatinine, and osteoporosis, as indicated by hip BMD and self-report in a population-based sample of U.S. women ≥ 50 years of age. Methods: We drew data from the National Health and Nutrition Examination Surveys for 1988-1994 (n = 3,207) and 1999-2004 (n = 1,051). Osteoporosis was indicated by hip BMD cut-offs based on the international standard and self-report of physician diagnosis. We analyzed U-Cd levels for association with osteoporosis using multiple logistic regression. Results: Women ≥ 50 years of age with U-Cd levels between 0.50 and 1.00 μg/g creatinine were at 43% greater risk for hip-BMD-defined osteoporosis, relative to those with levels ≤ 0.50 μg/g (odds ratio = 1.43; 95% confidence interval, 1.02-2.00; p = 0.04). We observed similar effect estimates using self-report of physician-diagnosed osteoporosis. Smokers did not show a statistically increased risk. Conclusions: Results suggest that U.S. women are at risk for osteoporosis at U-Cd levels below the U.S. Occupational Safety and Health Administration's 3-μg/g safety standard. Given null findings among smokers, dietary Cd, rather than tobacco, is the likely source of Cd-related osteoporosis risk for the U.S. female population ≥ 50 years of age.