Childhood and adolescent exposures and the risk of endometriosis.

BACKGROUND: Because endometriosis is diagnosed predominantly in young women, exposures occurring during childhood or adolescence may have a major impact on the disease. However, potential risk factors during this time period have received little attention. Our objective was to investigate relationships between childhood and adolescent exposures and the risk of endometriosis. METHODS: E3N is a prospective cohort of 98,995 French women aged 40-65 at enrollment in 1990. Follow-up questionnaires were sent every 2-3 years. Using a nested case-control design, we computed odds ratios (ORs) and 95% confidence intervals using unconditional logistic regression models. RESULTS: A total of 2684 endometriosis cases were reported as surgically ascertained among the 75,918 included women. There were inverse relationships of endometriosis risk with menarcheal age (test for trend, P < 0.0001) and with menstrual cycle length before 17 years of age (test for trend, P = 0.06), whereas menstrual cycle regularity before 17 years of age was not associated with risk. There were modest associations of endometriosis risk with exposure to pet animals (OR = 1.12 [95% confidence interval =1.02-1.22]) or living in a farm for 3 or more consecutive months during childhood (1.12 [1.02-1.24]), although with no link to any specific type of farm animal. In addition, there were positive linear associations between endometriosis risk and level of indoor exposure to passive smoking during childhood (up to 1.34 [1.09-1.64] with several hours exposure a day), experiencing food deprivation during World War II (1.34 [0.94-1.91]), and walking activity at 8-15 years of age (1.17 [1.05-1.31] for 5+ hours a week). CONCLUSIONS: This large study suggests that some exposures during childhood or adolescence may influence the risk of endometriosis. Further research is needed to confirm and better understand these relationships.