Evaluation of risk factors associated with endometriosis

To investigate the association between several factors such as demographics, personal habits, reproductive factors, menstrual characteristics, contraception, and clinical profile and the probability of having endometriosis.

Ten clinical institutions in the Montreal area.

A total of 2777 subjects who underwent surgery for diagnostic laparoscopy, tubal ligation, or hysterectomy between January 1998 and July 2002. Eight hundred ninety subjects were classified as cases on the basis of the presence of endometriotic lesions found at the time of surgery, whereas 1881 controls had no surgical evidence of endometriosis.

The association between potential risk factors and endometriosis was estimated by Pearson chi(2) and by crude and adjusted odds ratios.

Results indicated a positive association between endometriosis and education level for subjects who underwent hysterectomy. An inverse relation between gravidity and endometriosis was also found within a subgroup of subjects who had diagnostic laparoscopy. Furthermore, the proportion of uterine leiomyoma was significantly higher in cases compared with in controls, among subjects who underwent surgery for diagnostic laparoscopy or hysterectomy but not for tubal ligation.

These observations underline the importance of taking into account the clinical profile of subjects when investigating risk factors for endometriosis.