Contrary to some previous research, a new study from the US finds women’s risk of cardiovascular disease does not go up after having a hysterectomy in mid-life, with or without ovary removal. The risk is no higher than that faced by women who reach the menopause naturally, says the new study.

Lead author Karen A. Matthews of the University of Pittsburgh, and colleagues, write about their findings in a report due to be published online this week in the Journal of the American College of Cardiology.

Matthews, who is a distinguished professor of psychiatry and professor of epidemiology and psychology at Pittsburgh, declares in a press statement that the results should be encouraging to middle-aged women considering a hysterectomy:

“… our results suggest that increased levels of cardiovascular risk factors are not any more likely after hysterectomy relative to after natural menopause,” says Matthews.

Hysterectomy is a common surgical procedure that removes a woman’s uterus. Sometimes she also has her ovaries removed, usually to reduce risk of ovarian cancer.

However, while the need for such a procedure may be obvious, for instance because of cancer, prolapsed uterus, fibroids, or because of very heavy and painful periods, as with all surgery, the benefits have to be weighed against the risks.

Because of changes to hormones, one of the effects of having a hysterectomy before the menopause is that it usually brings on the menopause earlier.

Some previous studies have suggested hysterectomy raises long term risk of cardiovascular disease, which is the number one killer of women. And they have inferred that the risk is even higher if ovaries are also removed.

But there are objections to this view, mainly because those studies tended to evaluate cardiovascular disease risk factors years after hysterectomy and/or ovary removal without taking into account what they might have been before surgery.

For this new study, Matthews and colleagues followed 3,302 premenopausal women in the US for 11 years. The women were taking part in the Study of Women’s Health across the Nation (SWAN).

At the start of the study period, when the women enrolled on SWAN, they were between 42 and 52 years of age, had an intact uterus, at least one ovary, and were not taking hormone therapy.

They underwent assessments every year over the follow up, during which time the majority reached the menopause naturally, some had hysterectomy with ovary removal, and some had hysterectomy without ovary removal.

The main reasons for hysterectomy were fibroids, heavy periods, and chronic pelvic pain.

The researchers assessed cardiovascular disease risk factors in the participants before and after hysterectomy, and compared this to the risk factors before and after the final menstrual period in those who went through the menopause naturally.

Matthews and colleagues say their study is the first multiethnic study to track prospective annual changes in cardiovascular disease risk factors relative to hysterectomy or natural menopause.

The analysis showed that while some of the before and after individual cardiovascular risk factors changes were different for hysterectomy compared to natural menopause, overall, the pattern of changes did not suggest an increase in cardiovascular risk following hysterectomy say the researchers. And this was the same in all ethnic groups.

Plus, this was the case even after adjusting for possible influencers like Body Mass Index (BMI), which did go up after hysterectomy with ovary removal.

Mathews says they are not sure why their findings disagree with earlier studies that suggest hysterectomy raises cardiovascular disease risk.

One reason could be because they did not include younger women, and hysterectomy that occurs earlier in life may result in higher cardiovascular disease risk.

Another reason, says Matthews, could be that this study excluded women who had hysterectomies because of cancer.

SWAN is co-sponsored by the National Institute on Aging, the National Institute of Nursing Research, the National Institutes of Health, Office of Research on Women’s Health, and the National Center for Complementary and Alternative Medicine.

In 2011, writing in the journal Archives of Internal Medicine, researchers from the University of California at San Francisco reported finding women who underwent hysterectomy with ovary removal had a reduced risk of developing ovarian cancer, and no higher risk of developing other types of cancer, heart disease or hip fractures.

Written by Catharine Paddock PhD