NEW YORK -- Women who have their ovaries removed before menopause run a higher risk of developing dementia or other mental problems later in life -- unless they take estrogen until age 50, a study suggests.
Analysts said the research needs to be confirmed by further study, but the findings suggest another issue for women and their doctors to discuss as they consider ovary removal.
If they decide to go ahead with surgery, they need to consider the risks and benefits of taking estrogen to age 50, said Dr. Walter Rocca, a Mayo Clinic neurologist and lead study author.
Hormone therapy has been linked to a greater risk of dementia and heart attacks when given to women after age 65. But recent research indicates that when given before menopause or just after, it doesn't raise heart attack risk and might protect against dementia.
The study did not include women who had ovaries removed as part of cancer treatment, and Rocca said the results do not apply to such women. The work was published yesterday in the online edition of the journal Neurology.
Ovaries produce estrogen. Rocca said the most probable explanation of the study results is that removing ovaries causes a sudden deficiency of that hormone, which in turn affects the brain.
Hundreds of thousands of women have their ovaries removed each year in the United States. In women around age 45, approaching menopause, ovaries are often removed during hysterectomies as a precaution against developing ovarian cancer. In addition, some women at high risk of developing such cancer have ovaries removed without hysterectomies, as do others who have such problems as endometriosis.
Women younger than 45 often take estrogen after ovary removal because of such symptoms as hot flashes and concerns about developing osteoporosis, noted Dr. Nancy Chescheir of Vanderbilt University. Older women who have the surgery are less likely to start estrogen therapy, said Chescheir, who didn't participate in the new research.
The new study found that the risk of later mental impairment was higher when the surgery was done at younger ages.
The research examined about 1,500 women who had one or both ovaries removed from 1950 to 1987 and compared them with about 1,500 other women. Interviewers spoke with either the women themselves or somebody who knew them, asking about signs of memory impairment and any diagnosis of dementia or Alzheimer's disease.
The study found impairment or dementia in 150 of 1,489 women who'd had ovaries removed, versus 98 of 1,472 women who hadn't. That indicates about a 50 percent increase in risk.
A second study, which included about 2,300 women who had the surgery and about 2,400 who hadn't, found about a 70 percent increased risk for Parkinson's disease symptoms such as tremors.
Still, that outcome was far less common than mental impairment, and analysts said the evidence behind it was weaker. The Parkinson paper finding is "not quite ready for prime time" in terms of affecting patient care, said Dr. JoAnn Manson, chief of preventive medicine at Brigham and Women's Hospital in Boston. She was not involved with either study.