Is Endometriosis More Common and More Severe Than It Was 30 Years Ago?

Objective: Current estimates of endometriosis prevalence and incidence are highly variable, leading to uncertainty regarding true endometriosis frequency or validity of quantified changes over time. We present a comprehensive review of the prevalence, incidence, and stage of endometriosis worldwide as reported over the past 30 years.

Data sources: We conducted a systematic search of observational studies using the PubMed, Web of Science, EMBASE, and CINAHL databases to identify research papers published in English between January 1989 and June 2019. Search terminologies were limited to titles containing endometriosis and prevalence or incidence, or epidemiology, or frequency, or occurrence, or statistics.

Methods of study selection: Two independent reviewers screened abstracts for study eligibility, and data from included studies were abstracted.

Tabulation, integration, and results: Overall, 69 studies describing the prevalence and/or incidence of endometriosis met the inclusion criteria. Among these, 26 studies involved general population samples, 17 of which were from regional/national hospitals or insurance claims systems. The other 43 studies were conducted in single clinic or hospital settings. Prevalence estimates for endometriosis widely varied from 0.2% to 71.4% depending on the population sampled. The prevalence reported in general population studies ranged from 0.7% to 8.6%, whereas that reported in single clinic- or hospital-based studies ranged from 0.2% to 71.4%. When defined by indications for diagnosis, endometriosis prevalence ranged from 15.4% to 71.4% among women with chronic pelvic pain, 9.0% to 68.0% among women presenting with infertility, and 3.7% to 43.3% among women undergoing tubal sterilization. A meta-regression was conducted with year as the predictor of prevalence. No trend across time was observed among "general population in country/region" studies (β = 0.04, p = .12) or among "single hospital or clinic" studies (β = -0.02, p = .34); however, a decrease over time was observed among general population studies abstracted from health systems or insurance systems (β = -0.10, p = .005).

Conclusion: As with all human studies, population sampling and study design matter. Heterogeneity of inclusion and diagnostic criteria and selection bias overwhelmingly account for variability in endometriosis prevalence estimated across the literature. Thus, it is difficult to conclude if the lack of observed change in frequency and distribution of endometriosis over the past 30 years is valid.