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A recent study shows that women who have not yet gone through menopause and who undergo oophorectomy (surgical removal of the ovaries) have an increased risk of developing neurological disorders such as dementia and parkinsonism. The results come from two studies published in the online edition of "Neurology."

The research was done at the Mayo Clinic in Rochester, Minnesota and was based on women in Olmsted County, Minnesota, who underwent oophorectomies between 1950 and 1987 for a benign ovarian condition before the onset of menopause. Parkinsonism refers to any condition that causes the symptoms of Parkinson's disease, one of the most common age-related neurological disorders. These include tremor; stiffness of the arms, legs or trunk of the body; loss of facial expression; loss of control over movement; paralysis; and impaired mental processes (cognitive dysfunction).

The investigators interviewed 813 women who had one ovary removed, 676 with had both ovaries removed and 1,471 "controls" who were matched to the other women by age. Study participants were interviewed over the telephone to determine the rates of memory impairment, limitations in activities of daily living, and diagnosis of dementia, senility or Alzheimer's disease. The investigators also factored in the possible affects of age, educational level and history of depression.

Among subjects who had one or both ovaries removed, 150 had cognitive impairments or dementia, compared with 98 of the controls, a statistically significant difference.

In a second study using the same group of women, researchers found that women were 75 percent more likely to have parkinsonism if they had one ovary removed before 41 years of age. As was the case for cognitive impairment and dementia, the effect of surgery was age-dependent, the investigators report, and the risk increased with younger age at surgery.

The neuroprotective effect of estrogen may be general, the study posits, and may involve multiple mechanisms" and multiple type of brain cells.