Association between endocrine-disrupting chemicals and endometriosis : a systematic review and meta-analysis

Abstract

Background Endocrine-disrupting chemicals (EDCs) are substances widely and diversely existing in our environments and industrial products made with complex mixtures. EDCs have long biological half-lives and were accumulated in the organism and produce toxic or negative effects in several physiological processes, including reproductive system and endometriosis. Endometriosis has a prevalence of 6-10% in the world and has an increasing trend. It increases the social-economic burden, seriously decreases the female quality of life, and probably increases the risk of infertility. Some studies have explored the associations between the EDCs and risk of endometriosis, but without conclusive result. The study investigated the association between some endocrine disrupting chemicals and endometriosis from existing studies in the literature.

Methods Systematic review and meta-analysis were conducted to synthesize the eligible case-control and cohort studies reporting the associations between EDC exposure and endometriosis. The meta-analysis was conducted following the MOOSE guide-lines for Meta-Analysis and Systematic Review of Observational Studies. The processes of identification on eligible studies were performed. The author searched the Pubmed and Ovid Embase Classic using searching term in all field for publications of epidemiological studies; independent quality assessments were underwent in all included studies by the Newcastle-Ottawa Scale (NOS). I^2-statistics was calculated as the estimate of heterogeneity of the pooled effect estimates, funnel plot was used to assess the publication bias; the generic inverse of variance method for random models was used to calculate the pooled effect estimates. Sensitivity analysis was used to test the heterogeneity source in pooled effects estimate.

Results 14 eligible studies were identified. The meta-analysis showed that some EDCs such as total PCBs, PCB-118 and PCB-153 had significant associations with risks of endometriosis, increasing the risk of endometriosis by 106%, 72% and 128% respectively based on the current combined data; p’p’-DDE, PCB-138,PCB-156, PCB-170, PCB-180, MEP, MEHP, MBzP and HCB had insignificant associations with risks of endometriosis. No major publication bias was observed in this review. The sensitivity analysis showed study design may be one of the sources of heterogeneity for PCB-118 and PCB-153.

Conclusion Due to the limited number of included studies and moderate heterogeneity in included studies, further epidemiology research may explore the association between EDCs and endometriosis among nulliparity women who don’t have infertility and other estrogen-dependent disorders. Furthermore, except single PCB congeners, total PCBs is an important marker to evaluate the complex toxic association of PCBs on endometriosis. Steps to reduce environmental EDCs exposure and promote legislation or monitoring of toxic EDCs safety limits should be initiated to protect women from risk of endometriosis as earlier as it could.