1. This prospective study, using the US Nurses’ Health Study cohort, demonstrated a significantly higher risk of early natural menopause among women with endometriosis compared to those without a history of it.
2. The risk of early natural menopause among women with endometriosis was greater among those who were nulliparous and those who never used oral contraceptives.
Evidence Rating Level: 2 (Good)
Study Rundown: Early natural menopause (ENM) is associated with cardiovascular disease and early mortality. Endometriosis is a chronic inflammatory process where endometrial-like tissue grows outside the uterus. Whether endometriosis is a risk factor for ENM has yet to be fully elucidated. This prospective cohort study using 116 429 female, registered nurses from the US Nurses’ Health Study II examined whether there is an association between endometriosis and ENM risk. The primary outcome was menopause before age 45 (using three models). Other outcomes included ENM risk stratified by body mass index (BMI), smoking, oral contraceptive use, parity, and infertility due to ovulatory disorder. Females with laparoscopically confirmed endometriosis were at significantly greater risk of ENM than those without a history of endometriosis across all three models (model 1 showing the greatest magnitude of risk [HR: 1.51; 95% CI: 1.30-1.74] risk and model 3 showing the least, but still statistically significant, risk [HR: 1.28; 95% CI: 1.10-1.48]). BMI (<25 vs. >25), cigarette smoking status, and history of infertility attributed to ovulatory disorder demonstrated no differences in the association between endometriosis and ENM. However, oral contraceptive use (never vs. ever: HR: 2.03 [95% CI: 1.34-3.06] vs. 1.20 [95% CI: 1.02-1.42]; p for heterogeneity = 0.02) and parity (nulliparous vs. parous: HR: 1.46 [95% CI: 1.15-1.86] vs. 1.14 [95% CI: 0.94-1.39]; p for heterogeneity = 0.05) significantly increased the risk of ENM among women with endometriosis. Overall, endometriosis was associated with a higher risk of ENM; the risk increased among women with endometriosis who were nulliparous or never used oral contraceptives. One limitation of this study, however, is that menopause onset was self-reported, which could have resulted in the misclassification of some individuals.
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