Early life abuse and risk of endometriosis.

STUDY QUESTION: Is there an association between physical and sexual abuse occurring in childhood or adolescence and risk of laparoscopically-confirmed endometriosis?

SUMMARY ANSWER: Early life sexual and physical abuse was associated with an increased risk of endometriosis.

WHAT IS KNOWN ALREADY: Previous studies have reported that physical and sexual abuse are associated with chronic pelvic pain (CPP). However, only one study has examined the association between childhood physical abuse and laparoscopically-confirmed endometriosis, and did not observe an association with endometriosis risk.

STUDY DESIGN, SIZE, DURATION: Prospective cohort study using data collected from 60 595 premenopausal women from 1989 to 2013 as part of the Nurses' Health Study II cohort.

PARTICIPANTS/MATERIALS, SETTING, METHODS: Participants completed an exposure to violence victimization questionnaire in 2001. Cases were restricted to laparoscopically-confirmed endometriosis. Cox proportional hazards models were used to calculate rate ratios (RR) and 95% confidence intervals (CI).

MAIN RESULTS AND THE ROLE OF CHANCE: Three thousand three hundred and ninety-four cases of laparoscopically-confirmed endometriosis were diagnosed during 24 years of follow-up. Compared to those reporting no physical or sexual abuse, the risk of endometriosis was greater among those who experienced severe physical abuse (RR = 1.20; 95% CI = 1.06, 1.37) or severe sexual abuse (RR = 1.49; 95% CI = 1.24, 1.79). There was a 79% increased risk of laparoscopically-confirmed endometriosis for women reporting severe-chronic abuse of multiple types (95% CI = 1.44, 2.22). The associations between abuse and endometriosis were stronger among women presenting without infertility, a group that was more likely to have been symptomatic with respect to pain.

LIMITATIONS, REASONS FOR CAUTION: The violence exposure was recalled by the study participants and thus is subject to misclassification as well as recall bias for the cases who were diagnosed prior to 2001. However, our results were similar in a sensitivity analysis including only endometriosis cases incident after their violence history report. In addition, residual or unmeasured confounding is a possibility; however, we were able to adjust for a variety of potential early life confounders. Finally, selection bias is also a possibility if those who chose to return the violence questionnaire did so based jointly on abuse history and endometriosis risk.

WIDER IMPLICATIONS OF THE FINDINGS: Early life sexual and physical abuse was associated with an increased risk of endometriosis. Severity, chronicity and accumulation of types of abuse were associated with greater risk. Understanding the mechanisms underlying these relations may better define the biologic impacts of abuse and the related pathophysiology of endometriosis.

STUDY FUNDING/COMPETING INTEREST(s): This work was supported by National Institute of Child Health and Human Development [Grant numbers HD48544, HD52473, HD57210 and CA50385] and the Atlanta Clinical and Translational Science Institute [Grant number ULRR025008]. The Nurses' Health Study II is supported by the National Institutes of Health grant UM1 CA176726 from the National Cancer Institute. H.R.H. is supported by the National Cancer Institute, National Institutes of Health [Grant number K22 CA193860]. Authors report no conflict of interest.