Cardiovascular Disease and Cancer Risk Following Bilateral Oophorectomy: A Population-Based Study in Rochester, Minnesota

Increased cardiovascular mortality after early bilateral oophorectomy

OBJECTIVE

To investigate the mortality associated with cardiovascular diseases and the effect of estrogen treatment in women who underwent unilateral or bilateral oophorectomy before menopause.

DESIGN

We conducted a cohort study with long-term follow-up of women in Olmsted County, MN, who underwent either unilateral or bilateral oophorectomy before the onset of menopause from 1950 through 1987. Each member of the oophorectomy cohort was matched by age to a referent woman from the same population who had not undergone any oophorectomy. We studied the mortality associated with cardiovascular disease in a total of 1,274 women with unilateral oophorectomy, 1,091 women with bilateral oophorectomy, and 2,383 referent women.

RESULTS

Women who underwent unilateral oophorectomy experienced a reduced mortality associated with cardiovascular disease compared with referent women (hazard ratio [HR], 0.82; 95% CI, 0.67-0.99; P = 0.04). In contrast, women who underwent bilateral oophorectomy before age 45 years experienced an increased mortality associated with cardiovascular disease compared with referent women (HR, 1.44; 95% CI, 1.01-2.05; P = 0.04). Within this age stratum, the HR for mortality was significantly increased in women who were not treated with estrogen through age 45 years or longer (HR, 1.84; 95% CI, 1.27-2.68; P = 0.001) but not in women treated with estrogen (HR, 0.65; 95% CI, 0.30-1.41; P = 0.28; test of interaction, P = 0.01). Mortality was further increased after deaths associated with cerebrovascular causes were excluded.

CONCLUSIONS

Bilateral oophorectomy performed before age 45 years is associated with increased cardiovascular mortality, especially with cardiac mortality. However, estrogen treatment may reduce this risk.

Oophorectomy as a risk factor for coronary heart disease

OBJECTIVE

The objective of the study was to examine the relationship between bilateral oophorectomy (BSO) and risk of coronary heart disease (CHD).

STUDY DESIGN

We searched PubMed, EMBASE, meeting abstracts, and reference lists for studies that compared women with BSO at the time of hysterectomy with: (1) women with hysterectomy and ovarian conservation, (2) naturally menopausal women, (3) premenopausal women, or (4) women with no history of hysterectomy or BSO but unreported menopausal status. The primary outcome was fatal or nonfatal CHD.

RESULTS

We reviewed 1956 citations. Seven observational studies met inclusion criteria. Heterogeneity among studies precluded formal metaanalysis. Four studies reported BSO increases risk for CHD but only in some subgroups of women or not in fully adjusted multivariate models. Three studies found no increased risk of CHD following BSO, but these studies had significant limitations.

CONCLUSION

The existing evidence is inconclusive to determine the effect of BSO on risk of CHD.

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.

A comparative review of the risks and benefits of hormone replacement therapy regimens

The Women's Health Initiative (a large, randomized, placebo-controlled trial) investigated the effect of conjugated equine estrogens combined with medroxyprogesterone acetate on specific potential long-term benefits and risks. A review of the clinical studies that have investigated different types and regimens of estrogens combined with progestins was conducted to assess how applicable the results of the Women's Health Initiative are to hormone replacement therapy regimens in general. The studies that were reviewed were limited to randomized clinical trials and observational studies that have been published over the last 15 years (1987-2002) and to meta-analyses and reviews that may have included the literature before 1987. The increased risks for venous thromboembolism, stroke, coronary heart disease, and breast cancer that were identified in the Women's Health Initiative trial have also been reported with postmenopausal hormone therapies that contain a variety of estrogen and progestin products. The beneficial effects that were noted in the Women's Health Initiative, with respect to reductions in fractures and colorectal cancer, have not been evaluated in large, randomized controlled trials that use different estrogen/progestin combinations; however, observational trials that used a variety of estrogen or hormone replacement therapy products and randomized clinical studies that evaluated bone mineral density (an excellent predictor of fracture risk) with different estrogen/hormone replacement therapy regimens would suggest that results would be similar to those found in the Women's Health Initiative. Although the relief of menopausal symptoms, the primary reason women seek treatment, was not included in the overall benefit/risk analysis of the Women's Health Initiative, numerous trials suggest that all therapies are effective. Overall, these data indicate that the benefit/risk analysis that was reported in the Women's Health Initiative can be generalized to all postmenopausal hormone replacement therapy products.