Epidemiologic determinants of endometriosis: A hospital-based case-control study

PURPOSE: Risk factors for endometriosis were identified through data obtained from a case-control study at Brigham and Womenʹs Hospital in Boston, Massachusetts. METHODS: Cases were 50 women with infertility-associated endometriosis. The primary control group consisted of 89 fertile women without endometriosis, and an alternate control group consisted of 47 infertile women without endometriosis. RESULTS: The risk of endometriosis was positively associated with height (odds ratio (OR), 2.8 per 10 cm increase; 95% confidence interval (CI), 1.4–5.6) and inversely associated with weight (OR, 0.7 per 10 kg increase; 95% CI, 0.5 – 1.0) and body mass index (OR, 0.7 per 5 kg/m2 increase; 95% CI, 0.4 – 1.1). We observed an inverse association with exercise (OR, 0.6; 95% CI, 0.3 – 1.5), but the effect was limited to women who exercised greater-or-equal, slanted4 hours per week (OR, 0.4; 95% CI, 0.2 – 1.2). Endometriosis was not associated with either smoking or alcohol consumption. CONCLUSIONS: Our findings suggest that the fertility status of controls can strongly influence associations seen with menstrual characteristics. This study is one of few to address the issue of control selection for a case-control study of endometriosis. Specifically, potential problems encountered using fertile and infertile control women are examined and discussed.