September 12, 2007
Women who have their ovaries removed before menopause are at an increased risk of developing memory problems or dementia down the road. They may also be at increased risk of developing movement disorders such as Parkinson's disease. The findings, from a long-term study of women and memory, were reported in the online edition of Neurology, the medical journal of the American Academy of Neurology.
The ovaries produce key female sex hormones, including estrogen, which are important for reproductive function. Some research has also linked estrogen to brain health and memory. Younger women sometimes face ovary removal for medical reasons, such as ovarian cancer. Non-cancerous causes of ovary removal include cysts on the ovaries and endometriosis, as well as prevention of cancer for those at high risk.
The current study involved some 1,500 women who underwent the removal of one or both ovaries for non-cancer-related reasons. The women were compared to an equal number of women whose ovaries remained intact at the beginning of the study. All participants were followed for a median of 27 years and were interviewed about their memory. If the women could not be interviewed directly, the investigators talked to a family member.
Researchers found that women who had one or both ovaries removed before menopause were nearly two times more likely to develop thinking and memory problems than women who did not have the surgery. They were also more likely to develop Alzheimer's disease and other forms of dementia. The younger the women were when they had their ovaries removed, the more likely dementia was to develop.
"It's possible that estrogen has a protective effect on the brain and that a lack of estrogen due to ovary removal may increase a woman's risk of developing memory problems," said study author Dr. Walter A. Rocca of the Mayo Clinic in Rochester, Minnesota.
Age Window for Dementia
The study builds on earlier research that female hormones like estrogen may have memory-boosting benefits in younger, but not older, women. A study earlier this year, for example, found that women who use hormone therapy before age 65 may be able to cut their risk of developing Alzheimer's disease. [See the article, "Estrogen Use Before Age 65 Linked to Reduced Alzheimer's Risk."] In women older than 65, on the other hand, hormone therapy may actually increase the risk of Alzheimer's disease.
The current study provides further evidence that there may be a critical age window for the protective effect of estrogen on the brain in women. For example, the study found that women who had both ovaries removed before age 49, but were given estrogen treatment until at least age 50, did not have an increased risk of developing memory problems. "These findings suggest that estrogen is protective for these women in this age window," says Dr. Rocca.
Rocca adds that these findings should prompt physicians to reassess removing ovaries before menopause and the use of estrogen treatment following such surgery. "Although almost 60 percent of women received some estrogen treatment after both of their ovaries were removed, only 20 percent of them received estrogen treatment until at least age 50. Age 50 is the median age when women reach natural menopause."
Many of the women involved in the dementia study were also included in a larger study that found women who had one or more ovaries removed before menopause were nearly two times more likely to develop Parkinsonism, a syndrome involving tremor at rest, muscle rigidity, and slowness of movements. The most common form of this syndrome is Parkinson's disease. The risk for Parkinsonism increased with younger age at ovary removal. "Similar to the findings for dementia, these findings may be explained by a premature loss of estrogen and decreased neuroprotection," said Rocca.
The effects of estrogen on the brain are still not well understood. Additional studies are needed to assess the effects of hormones on cognitive and nervous function. Women considering ovary removal for medical reasons, and the use of hormone replacement therapy, should discuss the benefits and risks with their doctors.
Walter A. Rocca, MD, MPH, et al: Neurology, from the American Academy of Neurology. Online edition. August 29, 2007.
R Mayeux: "Can Estrogen or Selective Estrogen-Receptor Modulators Preserve Cognitive Function in Elderly Women?" (Editorial) New England Journal of Medicine, April 19, 2001, page 1242