Dementia Risk Linked to Ovary Removal

April 5, 2006 -- Women who undergo ovary removal before menopause may have an increased risk of dementia, a Mayo Clinic study suggests.

"What we are talking about is still-fertile women, finished with having children, who have some event that leads to surgery to remove their uterus, and the surgeon removes one or both ovaries to prevent cancer," study leader Walter Rocca, MD, MPH, tells WebMD.

The 2,511 women in the study had these operations between 1950 and 1987. The women were then matched with women who did not undergo ovary removal. Rocca's team determined whether the women developed dementia by interviewing a family member or by giving the women a test by telephone.

"What we showed is that for the surgery to be a risk factor, it has to be done before menopause," Rocca says. "If before age 46 you remove two ovaries, you get a 70% increased risk of dementia. And we discovered that women who have only one ovary removed before age 38 -- this is a surgery more often done in younger women -- we see a 260% increase in dementia. That is quite a dramatic and somewhat unexpected finding."

Rocca reported the findings at the annual meeting of the American Academy of Neurology in San Diego.

Opposing Views

Rocca expects his findings to be controversial. And they are. One skeptic is Paul Norris, MD, director of reproductive health at the University of Miami School of Medicine. Norris did not attend the AAN meeting but reviewed the written abstract of Rocca's study and a Mayo Clinic news release.

"I am raising both eyebrows as I read this," Norris tells WebMD. "There are a lot of reasons to keep the ovaries in, ranging from heart health to vagina health. But there is just no indication that it makes a difference in dementia."

There is, however, support for Rocca's theory. It comes from rat studies by Johns Hopkins neuropathologist Alena V. Savonenko, MD, PhD, and colleague Alicja Markowska, PhD, of the National Institute on Aging.

Savonenko and Markowska recently found that removing the ovaries of middle-aged rats sped the animals' age-related loss of mental function. Estrogen replacement -- if done on the proper schedule -- prevented this effect.

"I was surprised to see that there was so much similarity between Dr. Rocca's epidemiology study and our basic-science study in rats," Savonenko tells WebMD. "Our rats were absolutely doing the same thing as these women."

Still, Savonenko would be cautious in advising women not to undergo doctor-recommended ovary removal.

"I think there are very dramatic reasons why women undergo this surgery," she says. "I don't think the possible side effects on [mental function] should hold women from necessary ovary removal. But what I would suggest is consideration of estrogen replacement therapy for this cohort of women, particularly since there now is this evidence of cognitive decline."