A case-control epidemiologic study of endometriosis.

A case-control study involving 203 cases of pelvic endometriosis seen from 1987-1989, and 406 randomly selected and age-matched community controls was conducted in order to provide information relevant to effective prophylaxis of the disease. The diagnosis was confirmed by pathology from laparotomy and/or laparoscopy. A questionnaire focused on menstrual, marital and reproductive status, professional exposure and physical activities, and the results were analyzed by a conditional logistic regression model. Women characterized by earlier menarche (< or = 12 years) and longer period (> or = 8 days) were found to be associated with an elevated incurring risk, and a trend of increasing risk associated with primary dysmenorrhea (RR = 2.1 for mild to moderate and RR = 5.2 for severe dysmenorrhea), energetic physical activity during menstruation (RR = 2.1), and allergic diathesis (RR = 1.8) was seen. An inverse relationship was observed between the number of pregnancies and risk of endometriosis, and the protective effect was most significant when only the number of full-term pregnancies was counted. The risk factors of endometriosis are discussed, and intensive treatment of primary dysmenorrhea and avoidance of strenuous exercise during menstruation are identified as important measures in the prevention of endometriosis.