Higher body mass index (BMI) may lower the risk of developing endometriosis, a large analysis of previously published data demonstrated. The findings may point toward disease mechanisms involved in endometriosis.
Despite the rigorous analysis, researchers cautioned that the findings may, in fact, reflect a negative bias in diagnosing obese women.
The study, “Association between body mass index and endometriosis risk: a meta-analysis,” appeared in the journal Oncotarget.
Since earlier studies have reported contradicting results when examining a woman’s current BMI and risk for endometriosis, researchers at China’s Beijing Obstetrics and Gynecology Hospital, Capital Medical University performed what is known as a meta-analysis.
The method allows data from previously published studies to be pooled and analyzed together, providing a more robust result than individual studies. Researchers identified 11 studies that included enough data to be considered for the analysis. Nine were case-control studies and two were cohort studies, in which a group of patients is followed over time. The studies included 9,298 women diagnosed with endometriosis using medical examinations.
Researchers found that the risk of endometriosis fell by 33 percent for each 5 kg/m2 increase in BMI. Obese women had a 11 percent lower risk of developing the condition than women of normal weight. The numerically lower risk for overweight women was not statistically significant.
Looking separately at the fertility factor, the study showed that infertile women with a higher BMI had a lower risk than fertile women with a high BMI.
When the team included factors known to influence endometriosis risk — such as smoking status, length of menstrual cycle and age at menarche (first menstruation) — in the analysis, the association between BMI and endometriosis became somewhat weaker.
The team did not find any differences among studies from different parts of the world, as American, European and Asian studies all reported similar findings. When including only studies that fulfilled the highest-quality criteria, the result was again similar, suggesting that the finding was robust.
Although it is possible that the disease mechanisms that lead to endometriosis are less likely in women with higher BMI, researchers underscored that the findings may have other explanations.
For instance, they said their findings may reflect a diagnostic bias. Obese women with pelvic pain may be less likely to be offered a surgical examination, they argued. Since all the women in the study had a diagnosis confirmed by keyhole examination or other invasive procedures, this tendency may have skewed the results.
Further studies, examining if endometriosis disease mechanisms may be linked to processes at work in weight-determining processes, may contribute to further understanding.
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