The removal of a woman's ovaries before menopause creates a greater risk of both dementia and Parkinson's disease, two new studies report.

The findings are published in the Aug. 29 online edition of Neurology, the medical journal of the American Academy of Neurology.

If a woman's ovaries have been removed or a woman is experiencing menopausal symptoms, taking HRT, and continuing it for a year or two after menopause, might be beneficial, says a Canadian neuropsychologist.
(CBC)

The dementia study included approximately 1,500 women who underwent the removal of one or both ovaries for non-cancer-related reasons, such as ovarian cysts, endometriosis, or for the prevention of ovarian cancer. These women were compared with an equal number of women who still had both ovaries at the beginning of the study.

All participants were followed for a median of 27 years and were interviewed about their memory. Investigators interviewed a family member if the women couldn't provide accurate assessments of their memory themselves.

The study found that women who had one or both ovaries removed before menopause were nearly two times more likely to develop cognitive problems or dementia compared with women who did not have the surgery.

Many of the women involved in the dementia study were also included in a larger study that found women who had two ovaries removed before menopause or had one or both ovaries removed before age 42 were nearly two times more likely to develop Parkinsonism, a syndrome involving tremors, muscle rigidity and slowness of movements. 

Women who had one ovary removed after age 42 did not have an increased risk of Parkinson's.

Estrogen protects the brain, researchers believe

"We have one theory, which is the one that we think is the most logical or the most sensible," study author Walter Rocca, professor of neurology and epidemiology at the Mayo Clinic in Rochester, Minn., told CBC News.

"When you remove the ovaries in a young woman, you cause an estrogen deficiency. And if you do not compensate that with estrogen given from outside, that woman will be exposed to a known natural state of deprivation of estrogen." 

Jill Rich, a neuropsychologist at York University who studies memory, said there are a number of biological mechanisms suggesting estrogen is protective for the brain. She said there are estrogen receptors in the brain that reduce the formation of the kinds of plaques that are found in Alzheimer's disease.

"There are a lot of reasons to expect that estrogen would help to protect brains and delay or prevent the onset of dementia later on in life," she said.

She feels the study supports the body of research that says there is a critical period for hormone replacement therapy (HRT). She said if a woman's ovaries have been removed or a woman is experiencing menopausal symptoms, beginning HRT and continuing it for a year or two after menopause might be beneficial.

New way of looking at ovarian removal

Dr. Bobbie Gostout, a gynecologic surgeon at the Mayo Clinic, said the findings should change the way ovarian removal is viewed by doctors.

"The standard of care before this latest wave of information was to advise that women who were having a hysterectomy close to the age of natural menopause [to] consider having their ovaries removed in order to prevent ovarian cancer. The opportunity to remove the ovaries was seen as a real health advantage for women who were going to undergo surgery anyway.

"The new information that's come out has caused us to question that," she said.

Gostout believes that for women who have ovarian tumours or disease or a strong family history of ovarian cancer, the choice of ovary removal will definitely be seen as viable. But for those women with healthy ovaries who are electing to have them removed and are at low risk for ovarian cancer, doctors should proceed with caution, she said. 

"We want them to consider that having the ovaries in place may provide added benefits — especially the neuroprotective effect that's addressed in Dr. Rocco's studies."

Surgical choices require deliberation

For Natasha Matt-Hensruda, a 45-year-old Canadian mother of three, the choice to remove her uterus — but not her cystic ovary — nine weeks ago came after much deliberation.

"I had many options presented to me, from the very non-invasive, non-surgical options up to a hysterectomy, including removal of one or two ovaries.

"I decided that what was right for me was to proceed with the hysterectomy, but at all costs conserve as much ovarian function as possible."

She said all women should ask their doctors about all the options available to them.

"It's your right to ask questions and to be informed, to be an informed consumer. And I would also go as far as to say it's your responsibility because it's your body and you're going to live with that decision."