Urinary cadmium and osteoporosis in U.S. women age 50 and older, NHANES 1988-1994 and 1999-2004

Cadmium is a toxic metal that 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 below 1.0 μg cadmium/g creatinine. Our goal was to investigate the dose-response relationship between urinary cadmium and osteoporosis in a population-based sample of US women age 50 years and older. We hypothesized that cadmium levels between 0.50 and 1.0 µg/g creatinine might suggest a significant dose-response relationship. Data were pulled from the National Health and Nutrition Examination Surveys 1988-1994 (N=3207) and 1999-2004 (N=1051). Osteoporosis was indicated by hip BMD cutoffs based upon the international standard and self-report of physician diagnosis. Urinary cadmium levels were analyzed for association with osteoporosis using multiple logistic regression. Women age 50 years and older with urinary cadmium 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 at or below 0.50 μg/g (odds ratio (OR)=1.43; 95% CI=1.02, 2.00; p=0.03). Similar effect estimates were observed using self-report of physician-diagnosed osteoporosis. Smokers did not show a statistically increased risk. Results suggest that U.S. women are at risk for osteoporosis at urinary cadmium levels below the US Occupational Safety & Health Administration's 3 μg/g safety standard. Given null findings among smokers, dietary cadmium, rather than tobacco, is the likely source of cadmium-related osteoporosis risk for the U.S. female population age 50 and older.