Is body mass index associated with the incidence of endometriosis and the severity of dysmenorrhoea: a case–control study in China?

Objective Endometriosis is considered as a serious gynaecological disease in women at a reproductive age. Lower body mass index (BMI) is thought to be a risk factor. However, recent studies indicated that women with normal BMI were also more likely to develop endometriosis, suggesting the association with BMI is controversial. We therefore investigated the association of BMI and surgically diagnosed endometriosis in a cohort of Chinese women.Design Retrospective case–control study.Setting Tertiary hospital.Patients 709 women with endometriosis and 807 age matched controls between January 2018 and August 2019.Intervention Age at diagnosis, parity, gravida, BMI and self-reported dysmenorrhoea status were collected and the association of BMI and endometriosis was analysed.Measurement and main results Overall, the median BMI was not different between patients and controls (21.1 kg/m2 vs 20.9 kg/m2, p=0.223). According to the BMI categories for Asians/Chinese by WHO (underweight: