Researchers link low level urinary cadmium concentrations to osteoporosis

Researchers from Stony Brook University Medical Center have found that women in the United States who have urinary cadmium levels that are below the U.S. Occupational Safety & Health Administration safety standard are at risk for osteoporosis. While the study design is not sufficient to identify a causal link between cadmium and osteoporosis, the report revealed that women age 50 years and older who had higher levels of urinary cadmium than other women had a much greater risk for osteoporosis. The study findings are reported in Environmental Health Perspectives.

According to the World Health Organization, osteoporosis poses a disease burden that exceeds that of hypertension and breast cancer. The disease causes deterioration of bone tissue and increased fracture risk, particularly among women age 50 and older. Cadmium – a toxic metal found in foods, tobacco, drinking water and air – has been associated with decreased peripheral bone mineral density (BMD) and osteoporosis. The U.S. Occupational Safety & Health Administration considers the safety standard for urinary cadmium levels to be 3.00 microgram per gram creatinine or lower.

“Our study found that women age 50 years and older with urinary cadmium levels between 0.50 and 1.00 microgram per gram creatinine were at 43 percent greater risk for BMD-defined osteoporosis relative to those with levels at or below 0.50,” says Carolyn Gallagher, Lead Investigator and graduate student in the Graduate Program in Public Health. “These results show statistically significant associations between cadmium exposure and osteoporosis and between cadmium and BMD in the U.S. population. The findings are consistent with previously reported studies in Swedish, Belgian and Japanese populations.”

The researchers emphasise, however, that the SBUMC study is unique from the other similar studies because it is the only one that:

1. identified the cadmium/osteoporosis association in the U.S. population,
2. confirms osteoporosis using femoral BMD, the international standard for diagnosing osteoporosis, and
3. shows an association at or below cadmium levels of 1.00 microgram per gram creatinine or lower.

Two datasets were analysed for the study – the 1988-1994 National Health and Nutrition Examination Surveys (NHANES), which included 3,207 women age 50 years and older, and the 1999-2004 NHANES, which included 1,051 women age 50 to 85 years. NHANES is a cross-sectional survey that interviews, examines and conducts laboratory tests on sample U.S. civilians that is statistically representative of the U.S. population. In the first dataset, osteoporosis was indicated by hip BMD cut-offs based on the international standard. In the second dataset, osteoporosis was indicated by self-report of physician diagnosis.

After adjusting factors within the study population, the researchers also found that urinary cadmium was not significantly associated with osteoporosis among ever-smokers. This null finding among smokers leads the researchers to believe that dietary cadmium, rather than from tobacco, is the likely source of cadmium-related osteoporosis risk for the U.S. population of women age 50 and older.

The researchers further suggest that their findings, detailed in “Urinary Cadmium and Osteoporosis in U.S. Women Age 50 and Older, NHANES 1988-1994 and 1999-2004,” should prompt further investigation of the relationship between cadmium and osteoporosis, as well as a re-examination of the safety levels of cadmium in food, the most common source of cadmium exposure for the general population.

Ms. Gallagher’s colleagues in the study include Jaymie R. Meliker, Ph.D., Assistant Professor, Department of Preventive Medicine and Graduate Program in Public Health, and John S. Kovach, M.D., Professor, Department of Preventive Medicine.

Environmental Health Perspectives is a monthly journal of research and news on the impact of the environment on human health. The journal is published by the National Institute of Environmental Health Sciences and is the top ranked environmental science journal in the nation.

Part of Stony Brook University School of Medicine, the Graduate Program in Public Health seeks to advance the field of public health through application of the population health principles. The program vision is to improve the health of Long Island and regional populations though education, research, and community service.

(Source: Environmental Health Perspectives: Stony Brook University: July 2008)