Body fat may be linked with a reduced risk for women of developing endometriosis, researchers say today.
A major new study has found that morbidly obese women have a lower risk of endometriosis than slim women.
The research, using figures on more than 116,000 women, is published today (15 May) in the journal Human Reproduction.
Dr Divya Shah of the University of Iowa, USA, and colleagues looked at the possible link between body mass index (BMI), body shape and endometriosis. They explain that few studies have specifically explored this question.
Information on 116,430 female nurses was analysed. All were taking part in the Nurses’ Health Study II. Of the women, 5,504 had confirmed endometriosis.
Both BMI at age 18 and current BMI were significantly associated with endometriosis, that is, a higher BMI was linked to a lower risk. The pattern was stronger in infertile women. Infertile women with a current BMI of 35 to 39.9 had a 55% lower risk, and those with a BMI of 40 or more had a 62% lower risk, compared to women with a BMI of 18.5 to 22.4.
Waist-to-hip ration was also important – the risk of endometriosis was nearly three times higher in women a waist-to-hip ratio of 0.60 (that is, a smaller waist and larger hip) compared with a waist-to-hip ratio between 0.70 and 0.79.
The researchers say: "The results of this study suggest that endometriosis is inversely associated with early adult BMI and may correlate with a peripheral body fat distribution."
However, this does not show that low BMI causes endometriosis. The mechanisms behind the link are unclear, but is may be possible that BMI at a younger age influences health in later life due to an effect on hormones.
Shah, D. K.et al. Body size and endometriosis: results from 20 years of follow-up within the Nurses’ Health Study II prospective cohort. Human Reproduction 15 May 2013 doi:10.1093/humrep/det120
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