The association of body mass index with endometriosis and disease severity in women with pain

Introduction: There is a well-established inverse relationship between body mass index and frequency of endometriosis. However, these population-based studies have relied mostly on self-reported cases of endometriosis, rather than surgically confirmed endometriosis where disease severity has been objectively assessed. The aim of the current retrospective study was to establish whether the established relationship between endometriosis and low body mass index was independent of disease severity. Methods: Women with menstrual and/or pelvic pain undergoing laparoscopy for suspected endometriosis were recruited for this retrospective study (n=509). Women were grouped by body mass index (kg/m(2)) according to World Health Organization criteria: underweight (<18.5), normal (18.5-24.99), pre-obese (25-29.99) or obese (30). Endometriosis was scored according to the revised American Fertility Society system. Data were analysed based on body mass index and endometriosis status to identify any relationship between body mass index and disease. Results: The average body mass index of women with endometriosis was 25.0kg/m(2). The body mass index distribution of women with endometriosis differed relative to women in the general population. As expected, fewer obese women had endometriosis than in the lower body mass index categories. However, the obese women who did have endometriosis had significantly higher revised American Fertility Society scores compared to women with normal and pre-obese body mass indices. Discussion: Our results are consistent with the established finding of an inverse relationship between body mass index and endometriosis. The novel finding from this study is that obesity is associated with increased disease severity and reduced frequency of stage I endometriosis. It remains unclear what role body mass index has in the cause or effect of endometriosis; we speculate that body mass index may be useful for sub-classifying the disease.