Physical activity and endometriosis risk in women with infertility or pain : Systematic review and meta-analysis

Background:The potential association between endometriosis and physical activity (PA) has been suggested in several epidemiological studies.We aimed to establish whether PA influences endometriosis risk.Methods:MEDLINE and EMBASE were searched using physical activity OR exercise combined with endometriosis, in Medical Subject Headings and free text. We selected original articles in English, published up to April 2016, evaluating the association between endometriosis and recent or past PA (case-control or cohort studies). References of retrieved papers were reviewed. We computed summary odds ratios (ORs) of endometriosis for recent and past PA.Results:Six case-control and 3 cohort studies included 3355 cases for recent PA and 4600 cases for past PA. The summary OR for endometriosis according to PA level, calculated by the random-effect model, was 0.85 [95% confidence interval (CI) 0.67-1.07] for any recent versus no PA. As compared to no recent PA, ORs for low and moderate/high PA were 1.00 (95% CI: 0.68-1.28) and 0.75 (95% CI: 0.53-1.07), respectively.Conclusions:Though it suggests that PA may reduce the risk of endometriosis, this meta-analysis does not conclusively support the hypothesis. Whether our findings are really explained by the benefit of exercise at molecular and endocrine level, or related to confounding mechanisms, such as study design, choice of controls, and PA potentially improving pain, needs to be further investigated.