Most participants included in these analyses were white and were never smokers (). The proportion of ever HT users differed by primary exposure status (bilateral oophorectomy vs. natural menopause), at 96.8% among participants with bilateral oophorectomy and 66.3% among participants with natural menopause. Compared to participants with natural menopause, participants with a bilateral oophorectomy had a higher BMI, were more likely to be African American, had higher prevalence of high blood pressure, were more likely to have a family history of breast, ovarian, endometrial or cervical cancer, and were less likely to have a history of heart attack or myocardial infarction.
Baseline characteristics of 42,004 California Teachers Study participants with natural menopause or bilateral oophorectomy, by baseline status of menopausal hormone therapy (HT) use, 1995–2007
A total of 6,032 deaths occurred during an overall average follow-up of 11.3 years (); 1,028 deaths (17.0%) occurred among participants who reported a surgical menopause due to bilateral oophorectomy. Cardiovascular mortality and cancer mortality accounted for 2,067 (34.3%) and 1,754 (29.1%) deaths, respectively.
Having a surgical menopause due to bilateral oophorectomy, vs. having a natural menopause, was not associated with increased mortality in the CTS. For participants younger than 45 years of age at menopause, multivariable relative risks were 0.86 (95% CI, 0.74–1.00), 0.85 (95% CI, 0.66–1.11) and 0.91 (95% CI, 0.67–1.23) for all-cause mortality, cardiovascular mortality and cancer mortality, respectively (). For participants who were at least 45 years of age at menopause, bilateral oophorectomy was marginally associated with decreased all-cause mortality (RR, 0.87; 95% CI, 0.80–0.94), cardiovascular mortality (RR, 0.83; 95% CI, 0.71–0.96) and cancer
mortality (RR, 0.84; 95% CI, 0.72–0.98).
Relative risks (RR) and 95% confidence intervals (CI) of all-cause and cause-specific mortality, overall and by age at natural menopause or age at bilateral oophorectomy in 42,004 participants in the California Teachers Study, 1995–2007
Bilateral oophorectomy did not appear to confer mortality protection independent of that provided by HT use. Among women of all ages combined, using natural menopause and never use of HT as the reference group, bilateral oophorectomy in never HT users was not statistically significantly associated with all-cause mortality (RR, 0.94; 95% CI, 0.76–1.16), cardiovascular mortality (RR, 0.95; 95% CI, 0.69–1.31) or cancer mortality (RR, 0.89; 95% CI, 0.55–1.45). The relative risks for bilateral oophorectomy in ever HT users were 0.79 (95% CI, 0.73–0.86) for allcause
mortality, 0.77 (95% CI, 0.67–0.88) for cardiovascular mortality and 0.78 (95% CI, 0.67–0.90) for cancer mortality. Stratification by age at menopause (<45 vs. ≥45), did not change these results markedly. Investigation of the association between primary exposure status (surgical menopause due to bilateral oophorectomy vs. natural menopause) and mortality by HT formulation showed no clear statistically significant differences by formulation ().
Table 3 Relative risks (RR) and 95% confidence intervals (CI) of all-cause and cause-specific mortality by ever use of menopausal hormone therapy (HT) in the form of estrogen therapy (ET) or estrogen plus progestin therapy (EPT), overall and by age at natural (more ...)
In several additional analyses we assessed whether results were dependent on the definition of reference group. In one such analysis we excluded participants who reported experiencing a natural menopause but who had a hysterectomy at a later date (n=3,815). Results did not differ significantly from those presented and are thus not shown.