Tobacco smoking and risk of endometriosis: a systematic review and meta-analysis

Abstract

ObjectiveSince conflicting results have been published on the role of tobacco smoking on the risk of endometriosis, we provide an up-to-date summary quantification of this potential association.DesignWe performed a PubMed/MEDLINE search of the relevant publications up to September 2014, considering studies on humans published in English. We searched the reference list of the identified papers to find other relevant publications. Case–control as well as cohort studies have been included reporting risk estimates on the association between tobacco smoking and endometriosis. 38 of the 1758 screened papers met the inclusion criteria. The selected studies included a total of 13 129 women diagnosed with endometriosis.SettingAcademic hospitals.Main outcome measureRisk of endometriosis in tobacco smokers.ResultsWe obtained the summary estimates of the relative risk (RR) using the random effect model, and assessed the heterogeneity among studies using the χ2 test and quantified it using the I2 statistic. As compared to never-smokers, the summary RR were 0.96 (95% CI 0.86 to 1.08) for ever smokers, 0.95 (95% CI 0.81 to 1.11) for former smokers, 0.92 (95% CI 0.82 to 1.04) for current smokers, 0.87 (95% CI 0.70 to 1.07) for moderate smokers and 0.93 (95% CI 0.69 to 1.26) for heavy smokers.ConclusionsThe present meta-analysis provided no evidence for an association between tobacco smoking and the risk of endometriosis. The results were consistent considering ever, former, current, moderate and heavy smokers, and across type of endometriosis and study design.

Reproductive and Lifestyle Factors Associated with Endometriosis in a Large Cross-Sectional Population Sample

“…Our study is in line with a previous large meta-analysis 25 and other studies 6,17,26,45 and further strengthens that there is no association between smoking and endometriosis.…”

“…22 Smoking has shown to be either protective 23,24 or not to be associated with the disease. 25,26 A meta-analysis indicated an association between alcohol consumption and endometriosis. 27 …”

Why so null? Methodologic necessities to advance endometriosis discovery

“…In addition to the superficial peritoneal, endometrioma, and deep endometriosis macro‐phenotypes, symptomatology may help to define informative subtypes with heterogeneous risk factor profiles. While a null association with serum cotinine levels was observed in this study, in line with a meta‐analysis, neither considered case heterogeneity. Indeed, for the meta‐analysis, when results were presented stratified by case and/or control categories, they were pooled regardless of observed effect modification and the summary effect incorporated .…”

Modifiable life style factors and risk for incident endometriosis

“…Tobacco may alter aromatase as well as increase the body's inflammatory response . One systematic review concluded there was no association between smoking and endometriosis; however, most studies included in the analysis were based on self‐report and report crude estimates of association …”