Survival patterns after oophorectomy in premenopausal women: a population-based cohort study

BACKGROUND: A statistical model of death due to ovarian cancer, breast cancer, coronary heart disease, hip fracture, and stroke has suggested that women who undergo prophylactic bilateral oophorectomy are at increased risk of death for all causes. We aimed to investigate survival patterns in a population-based sample of women who had received an oophorectomy and compare these with women who had not received an oophorectomy. METHODS: From an existing cohort of all women who underwent unilateral or bilateral oophorectomy while residing in Olmsted County, MN, USA, in 1950-87, we analysed those who had received an oophorectomy for a non-cancer indication before the onset of menopause. Every member of the cohort was matched by age to a referent woman in the same population who had not undergone oophorectomy. 1293 women with unilateral oophorectomy, 1097 with bilateral oophorectomy, and 2390 referent women were eligible for the study. Women were followed up until death or the end of the study (staggered over 2001-06) by use of direct or proxy interviews, medical records in a records-linkage system, and death certificates. FINDINGS: Overall, mortality was not increased in women who underwent bilateral oophorectomy compared with referent women. However, mortality was significantly higher in women who had received prophylactic bilateral oophorectomy before the age of 45 years than in referent women (hazard ratio 1.67 [95% CI 1.16-2.40], p=0.006). This increased mortality was seen mainly in women who had not received oestrogen up to the age of 45 years. No increased mortality was recorded in women who underwent unilateral oophorectomy in either overall or stratified analyses. INTERPRETATION: Although prophylactic bilateral oophorectomy undertaken before age 45 years is associated with increased mortality, whether it is causal or merely a marker of underlying risk is uncertain.