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Date of release: 23 January, 2012

Surgical menopause and early mortality in the California Teachers Study


The California Teachers Study is a prospective cohort study initiated in 1995–1996 using mailed, self-administered questionnaires. This recently published sub-study compared mortality in 9,785 participants who had a surgical menopause and 32,219 who had a natural menopause [1]. All-cause, cardiovascular and cancer mortality rates were obtained from three Californian data banks and compared to menopausal hormone therapy (HT) use. 


 


Among participants with bilateral oophorectomy aged < 45 years at menopause, relative risks (95% confidence interval) for death were 0.86 (0.74–1.00), 0.85 (0.66–1.11) and 0.91 (0.67–1.23) for all-cause, cardiovascular and cancer mortality, respectively. For those over age 45, the corresponding data were 0.87 (0.80–0.94), 0.83 (0.71–0.96) and 0.84 (0.72–0.98). The association between bilateral oophorectomy and mortality did not differ by baseline status of hormone use. The authors concluded that surgical menopause due to bilateral oophorectomy vs. natural menopause does not increase all-cause, cardiovascular or cancer mortality.

Comment

This conclusion needs to have the caveat that 56% of women in this study with a natural menopause had used HT and 91% of those with a surgical menopause used HT. Thus, the beneficial effects could have been due to the high use of HT. There was inadequate power to measure any effect of bilateral oophorectomy on those who did not use HT. Other similar cohort studies from the Mayo Clinic and the Nurses Health Study have shown increased mortality after early surgical menopause [2,3]. The California Teachers Study is a respected ongoing large study of 133,479 women. In this sub-study, there were many reasons for exclusion and only 42,004 were finally analyzed. The study did not address the issue of bilateral oophorectomy when hysterectomy is required after menopause. The strengths of this study include the quality of the data from the three linked registries and databases and direct information from the women themselves at study entry. The potential weaknesses of the study include the relatively short time of follow-up (mean 11.3 years) to observe mortality outcomes (it did not assess morbidity or health-related quality of life in the 83% still living), the reasons for oophorectomy were not collected, and there could have been co-morbidities associated with both surgical and early natural menopause, and lastly the potential for immortal time bias, i.e. with variable times from oophorectomy to study entry, women could have died in that interval and not be counted. Our clinical message is that premenopausal bilateral oophorectomy must still be individualized and considered, e.g. where there is ovarian pathology or a strong family history of ovarian cancer. However, most gynecologists with a menopause practice will want to ere on the side of ovarian conservation at the time of hysterectomy. If performed, then early HT after surgical menopause appears to ameliorate any possible increased risk of all-cause mortality from premature ovarian hormone loss and was not associated with increased cancer mortality. In all the sub-analyses of HT after either natural or surgical menopause, all-cause, cardiovascular or cancer mortalities were either significantly reduced or there was a non-significant trend to reduced mortality in the users of HT compared to never-users. This is reassuring and is in concert with the critical window of benefit hypothesis when HT is used from near menopause.

Comentario

Alastair and Alice MacLennan
The Discipline of Obstetrics & Gynaecology, The University of Adelaide, South Australia

    References

  1. Duan L, Xu X, Koebnick C, Lacey JV, et al. Bilateral oophorectomy is not associated with increased mortality: the California Teachers Study. Fertil Steril 2011 Nov 14. E-pub ahead of print.
    http://www.ncbi.nlm.nih.gov/pubmed/22088205

  2. Rocca WA, Grossardt BR, de Andrade M, Malkasian GD, Melton U. Survival patterns after oophorectomy in premenopausal women: a population-based study. Lancet Oncol 2006;7:821-8.
    http://www.ncbi.nlm.nih.gov/pubmed/17012044

  3. Parker WH, Broder MS, Chang E, et al. Ovarian conservation at the time of hysterectomy and long-term health outcomes in the Nurses Health Study. Obstet Gynecol 2009;113:1027-37.
    http://www.ncbi.nlm.nih.gov/pubmed/19384117