Prior Mayo Clinic epidemiologic and laboratory studies have pointed to a role for estrogen in defending the brain from attack as a woman ages. "We conducted a previous study suggesting that hysterectomy, that is, removing the uterus, and younger age at menopause are related to an increased risk of Parkinson's disease," says Dr. Rocca. "These findings suggested that the estrogen produced normally by the ovaries is involved in protecting the brain during aging.
"Also, there is biological evidence from animal studies that estrogen is protective for the specific part of the brain that is involved in controlling movements," he says. "Damage to this part results in Parkinson's disease. If an animal receives a toxic chemical able to destroy the cells of this part of the brain along with estrogen, the damage will be reduced compared to injecting the toxic substance alone."
Dr. Rocca indicates that the design of the current study does not provide the data needed to address the question of whether a woman's risk of parkinsonism after having both ovaries removed is altered by taking estrogen therapy.
The Mayo Clinic investigators studied 1,202 women who had both ovaries surgically removed and 1,283 women who had one ovary surgically removed. All women were recruited from the general population of Olmsted County, Minn., from 1950 through 1987. For each woman who underwent ovarian surgery, the researchers selected a woman of the same age who did not undergo ovarian surgery. All the women studied were followed through the onset of parkinsonism or Parkinson's disease, death, loss to follow up or the time the study was conducted.
Among women who had no ovaries removed, 29 cases of parkinsonism developed, 18 of which were Parkinson's disease. In contrast, among women who had one or bo
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