A systematic review on the prevalence of endometriosis in women

Yousef Moradi, Shams-Beyranvand M, Mehran Shams-Beyranvand, Khateri S, Sorour Khateri, Gharahjeh S, Saeedeh Gharahjeh, Tehrani S, Shahrzad Tehrani, Fatemeh Varse, Varse F, Amir Tiyuri, Najmi Z, Zahra Najmi
The Indian journal of medical research · 2021 · vol. 154(3) , pp. 446–454 · doi:10.4103/ijmr.ijmr_817_18 · PMID:35345070 · PMC9131783 · W4285550026
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This systematic review and meta-analysis estimated the overall prevalence of endometriosis at 18%, with variations based on disease stage and clinical symptoms like infertility and pain.

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This systematic review and meta-analysis searched MEDLINE, Web of Science, Google Scholar, Scopus, and CINAHL for cross-sectional, peer-reviewed studies published from January 1990 to December 2018 that reported the prevalence of endometriosis in women aged 15–60 years, including subgroup analyses by disease stage, diagnostic method, geographical distribution, clinical symptoms, and sample size. Seventeen studies totaling 127,476 women were included, and the pooled prevalence of endometriosis was 18% (95% CI: 16–20), with prevalence by stage ranging from 2% for stage 4 (95% CI: 1–4) to 20% for stage 1 (95% CI: 11–28). Prevalence was reported as 31% (95% CI: 15–48) in women with infertility, 42% (95% CI: 25–58) in those with chronic pelvic pain, and 23% (95% CI: 19–26) in asymptomatic women, using random-effects models and assessing heterogeneity and publication bias. The paper’s explicit limitation is that it relies on cross-sectional studies, and the included studies varied in diagnostic approaches and quality (with several rated poor). This paper is centrally about endometriosis — estimating and meta-analyzing the prevalence of endometriosis across stages, symptoms, and diagnostic methods.

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Abstract

Background & objectives: Endometriosis is one of the causes of female infertility, but the prevalence of endometriosis is not exactly known. We conducted a systematic review and meta-analysis to provide an estimate of the prevalence of endometriosis in women considering the stage of disease, diagnostic method, geographical distribution, clinical symptoms and sample size. Methods: MEDLINE, Web of Science, Google Scholar, Scopus and Cumulative Index of Nursing and Allied Health were searched to identify peer-reviewed studies published from January 1990 to December 2018 reporting the prevalence of endometriosis. Relevant additional articles were identified from the lists of the retrieved articles. Studies with cross-sectional design were included in the meta-analysis. Results: The overall prevalence of endometriosis was 18 per cent [95% confidence interval (CI): 16-20] and the prevalence of endometriosis by stage ranged from two per cent (95% CI: 1-4) for stage 4 to 20 per cent (95% CI: 11-28) for stage 1. The prevalence levels of endometriosis in women with infertility, chronic pelvic pain and asymptomatic were 31 (95% CI: 15-48), 42 (95% CI: 25-58) and 23 per cent (95% CI: 19-26), respectively. Interpretation & conclusions: The results of this study showed that the prevalence of endometriosis in developing countries was high. Future studies are needed to explore other factors affecting the prevalence of endometriosis worldwide, which may help develop future prevention programmes.
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Results

A total of 2433 articles were extracted for this study. Finally, 17 studies 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 with 127,476 women suffering from endometriosis were included for estimating the prevalence of endometriosis ( Fig. 1 ). The characteristics of the included studies are described in Table I . The quality assessment details for the included studies are shown in Table II . Flow diagram showing literature search and study selection. Characteristics of the included studies MRI, magnetic resonance imaging Quality assessment of included articles based on Quality Assesment Tool for observational cohort & cross-sectional studies 11 . CD, cannot determine; NA, not applicable; NR, not reported A meta-analysis was conducted regarding the stage of the disease, diagnostic method, continent and clinical symptoms to estimate the prevalence of endometriosis. The pooled prevalence estimate of endometriosis regardless of the stage of disease, diagnostic method, continent and clinical symptoms was 18 per cent [95% confidence interval (CI): 16-20; Fig. 2 ]. The prevalence of endometriosis based on the stage of the disease ranged from two per cent (95% CI: 1-4) for stage 4 to 20 per cent (95% CI: 11-28) for stage 1 ( Table III ). Pooled prevalence estimate of endometriosis. Pooled prevalence estimates along with 95% confidence intervals of endometriosis by stage of disease, diagnostic method and continent * P <0.05. MRI, magnetic resonance imaging; CI, confidence interval The prevalence of endometriosis by the diagnostic method ranged from 12 per cent (95% CI: 3-21) for endometriosis diagnosed with other diagnostic methods to 20 per cent (95% CI: 17-22) for endometriosis diagnosed with laparoscopic method ( Table III ). The CI of Egger’s test did not include zero, showing significant publication bias ( Fig. 3 ). Furthermore, high statistical heterogeneity ( I 2 >99%, P <0.001) was identified in total analyses ( Table III ). Funnel plot for pooled prevalence estimate by different stages of endometriosis. The prevalence of endometriosis by the continent ranged from 17 per cent (95% CI: 12-21) for Europe to 36 per cent (95% CI: 5-69) for Asia, and by the sample size ranged from 28 per cent (95% CI: 19-37) for studies with less than of 1000 individuals to seven per cent (95% CI: 3-11) for studies with more than of 1000 individuals ( Table III ). The results of subgroup analysis indicated that the prevalence rates of endometriosis in women with infertility, chronic pelvic pain and asymptomatic women were 31 (95% CI: 15-48), 42 (95% CI: 25-58) and 23 per cent (95% CI: 19-26), respectively ( Table III ). Meta-regression was used to explore the sources of between-study heterogeneity including age and diagnostic method. According to the results, the prevalence of endometriosis did not show a relationship with age ( P >0.10) and diagnostic method ( P >0.10).

Discussion

Regarding the stage of endometriosis, the results of this study showed that the prevalence of minimal endometriosis (stage 1) was higher than other stages of endometriosis. Considering the diagnostic method, the prevalence of endometriosis diagnosed with laparoscopy, ultrasound and magnetic resonance imaging (MRI) methods was higher than endometriosis diagnosed with other diagnostic methods in the world. Another study showed the same results 30 . The precise prevalence of endometriosis in female adult population is not known. The prevalence in fertile women undergoing sterilization is four per cent (1.5-5%), whereas it is 13.5 per cent (2-68%) in infertile women 5 . The reported prevalence of this disease in women undergoing laparoscopy for chronic pelvic pain ranged from 15 to 75 per cent 6 . A study conducted in north India in 2015 showed that the precise prevalence of endometriosis was not known; however, it was estimated to be 2-10 per cent in the general population, but up to 50 per cent in infertile women 31 . Endometriosis affects approximately 70 per cent of women with dysmenorrhoea and dyspareunia 32 . Adolescents may have more severe symptoms. Reports from Germany showed that 0.05, 1.93 and 6.1 per cent of the patients were in the age groups of 10-14, 15-19 and 20-24 yr, respectively 33 34 35 . A review of previous studies indicated that global estimates varied significantly and ranged from approximately 2-45 per cent based on the diagnostic criteria and the study population 35 . The world statistics suggest that 10-15 per cent of women in the world are affected by endometriosis, which is consistent with the results of our study, as the overall prevalence was estimated to be 18 per cent 35 . According to our analysis, the prevalence of endometriosis in developing countries was higher than in developed countries as also shown by another study 36 . The present study had several limitations. First, the number of studies in some subgroups was small and did not provide sufficient statistical power to assess the source of heterogeneity. Second, there were some other factors (such as diagnostic accuracy, quality of detective equipment and physicians’ skills in detecting endometriosis) that might be important sources of heterogeneity, but we could not evaluate their role in heterogeneity due to the lack of information. Third, some of the included studies did not measure the variables such as age or prevalence of endometriosis by the stage of the disease. Despite the high heterogeneity of the studies, this systematic review and meta-analysis showed a high prevalence of endometriosis in developing countries. The prevalence of endometriosis in women with chronic pelvic pain was higher than those with infertility. Future studies are needed to explore factors affecting endometriosis prevalence worldwide, which may help develop future prevention programmes.

Material|Methods

Search strategy : All international databases including MEDLINE, Web of Science, Google scholar, Scopus and Cumulative Index to Nursing and Allied Health Literature were searched for the original articles without language and time limitation, written from January 1990 to December 2018. Keywords were searched electronically by two independent Boolean operators using a specified search strategy. The protocol of this study was registered in the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42017075275) 8 . Inclusion/exclusion criteria : Two reviewers independently carried out the literature search and evaluation of the searched articles based on the inclusion and exclusion criteria. The structures of the searched articles were appraised by the reconstructed PRISMA checklist 9 . All the articles with full text in English conducted as a cross-sectional design reporting the prevalence of endometriosis in any stage of the disease in women aged 15-60 yr old, were include. Data extraction : Using a uniform excel sheet, two reviewers independently extracted the required data from the data contained in the identified articles. Discrepancies in the extracted data were resolved through consensus, and if agreement could not be reached, they resolved it by referral to a third investigator. The STROBE checklist 10 was used as a standard checklist for reporting the results of the included studies. Quality assessment and risk of bias : The quality of each study was assessed according to the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies 11 which included the quality of research question, study population, sampling strategy, groups recruited from the same population and uniform eligibility criteria, sample size justification, exposure assessed before outcome measurement, sufficient timeframe to observe an effect, different levels of the exposure of interest, exposure measurement and assessment, repeated exposure assessment, outcome measurement, blinding of outcome assessors, follow up rate and statistical analyses. This tool measures 14 different criteria which are used to give each study an overall quality rating of good, fair or poor. Statistical analysis : Random effects models were used based on the presence of heterogeneity. Heterogeneity was assessed using Q Cochran’s test and I 2 index 12 . The forest plot was implemented for showing the results of the individual and pooled effects of all the studies. The Egger’s test was also used to evaluate the presence of publication bias 12 . In addition, a subgroup analysis was done (by sample size, stages of endometriosis, diagnostic method, continent and clinical symptoms) to identify different sources of heterogeneity. A P <0.05 was considered significant for all statistical tests, except for Q Cochran’s, meta-regression and Egger’s test (<0.1). All statistical analyses were performed through STATA version 12.0 (STATA Corp., College Station, TX, USA).

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Condition tags

endometriosischronic_pelvic_paininfertility

MeSH descriptors

Endometriosis Endometriosis Endometriosis Endometriosis Infertility, Female Infertility, Female Infertility, Female Infertility, Female Cross-Sectional Studies Cross-Sectional Studies Cross-Sectional Studies Female Female Female Humans Humans Humans Prevalence Prevalence Prevalence

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