The influence of unilateral oophorectomy on the age of menopause

Objective: To determine the age of menopause after premenopausal unilateral oophorectomy (UO) and to establish whether UO at a young age leads to menopause at a younger age than if UO occurs at an older age.Methods: A cohort of 28 731 women, of whom 17 781 (62%) were menopausal, was investigated. Information on menopause was obtained from self-reported questionnaires. Surgical data were obtained from the National Patient Register to avoid recollection bias. Age of menopause after UO/not UO was determined using Kaplan–Meier curves. Cox regression was used to identify factors of importance for early menopause.Results: UO was performed in 1148 women. Women with UO after the age of 45 years, premenopausal hysterectomy, bilateral oophorectomy and cancer were excluded, leaving 236 in the analysis. Menopause occurred 1.8 years earlier after UO compared to women with two intact ovaries (mean 49.5 vs. 51.3 years), and younger age at UO was significantly linearly correlated to younger age at menopause. UO (hazard ratio 1.23) and smoking (hazard ratio 1.12) significantly decreased the age of menopause.Conclusions: Premenopausal unilateral oophorectomy significantly reduces the age of menopause by 1.8 years. Younger age at UO leads to significantly younger age at menopause.