The association between heavy metals, endometriosis and uterine myomas among premenopausal women: National Health and Nutrition Examination Survey 1999-2002.

BACKGROUND: It has been hypothesized that exposure to exogenous estrogens may be associated with endometriosis and uterine myomas. We sought to investigate the association between heavy metals which have been shown to be hormonally active and these disorders using data from the National Health and Nutrition Examination Survey, 1999-2002.
METHODS: Women aged 20-49 years who had data on metals and the outcomes of interest, were premenopausal and neither pregnant nor breastfeeding were eligible (n = 1425). Lead, cadmium and mercury were measured in whole blood. Diagnosis of outcomes was based upon self-report. Logistic regression was used to examine the association between tertiles of heavy metals and disease adjusting for age, race/ethnicity, use of birth control pills prior to diagnosis and smoking status at diagnosis.
RESULTS: A dose-response association between cadmium and endometriosis was observed [tertile 2 versus 1: adjusted odds ratio (OR) = 1.94, 95% confidence interval (CI): 0.73-5.18; tertile 3 versus 1: adjusted OR = 3.39, 95% CI 1.37-8.40]. This association persisted in subanalyses: (i) limiting analysis to women diagnosed in the past 10 years and (ii) limiting analysis to women diagnosed since last pregnancy, although limited by sample size.
CONCLUSIONS: These results must be interpreted with caution given the cross-sectional study design. The observed association between cadmium and endometriosis deserves further investigation in properly designed studies.