THURSDAY, April 14, 2005 (HealthDay News) -- The removal of both ovaries in young women may double their risk of developing Parkinson's disease later in life, a new study finds.
The researchers also found that the younger the woman was at the time of her surgery, the more her risk went up.
"It is well-established, as of today, that removal of both ovaries is associated with later development of Parkinson's disease and parkinsonism [symptoms of the disorder]," said study author Dr. Walter Rocca, a neurologist and epidemiologist at the Mayo Clinic in Rochester, Minn.
Surgical removal of the ovaries often takes place when a woman is diagnosed with ovarian cancer or is having abdominal surgery, such as a hysterectomy or the removal of cysts. In cases where the surgery is elective, Rocca said his study may influence a woman's decision about whether or not to have her ovaries removed.
His team reported the results on April 13 at the American Academy of Neurology annual meeting in Miami Beach, Fla.
The researchers studied 1,202 women who had both ovaries surgically removed, and 1,283 women with one ovary removed. All of the women had surgery between 1950 and 1987 in Olmsted County, Minn. Study investigators also followed a comparison group of women who did not have ovarian surgery.
The women were tracked an average of 25 to 30 years. Among the women who had ovaries removed, the researchers found 51 cases of parkinsonism, 25 of which were Parkinson's disease. By comparison, the researchers found 29 cases of parkinsonism --18 of which were Parkinson's disease -- among the women who had not had ovarian surgery.
The risk of developing Parkinson's disease or parkinsonism was most pronounced among women who had had both ovaries removed, Rocca noted. "When we looked at the women with bilateral oophorectomy, there was almost a doubling of the risk," he said. The findings were also suggestive of an increased risk for women who had one ovary removed, but they were not statistically significant.
Parkinson's disease is caused by damage to neurons in the brain that produce dopamine, which aids in the smooth, coordinated function of the body's muscles and movement. People with Parkinson's disease experience tremor, slowness of movement, rigidity and difficulty with balance. According to the National Parkinson's Foundation, about 1.5 million Americans have the disease.
The researchers suspect that it is the loss of naturally occurring estrogen early in life that accounts for the increased risk in women who lose their ovaries. Previous studies have suggested estrogen helps protect the brain as it ages, Rocca said.
This would help explain why the risk is greater the younger a woman is at the time of her surgery, he said.
Rocca said estrogen-replacement therapy is recommended for premenopausal women who have had both ovaries removed. The use of hormone replacement therapy in postmenopausal women has been a matter of controversy in recent years because studies have shown it can increase a woman's risk of cardiovascular disease and breast cancer.
Because of those concerns, Dr. Andrew Siderowf, an assistant professor of neurology at the University of Pennsylvania, in Philadelphia, said he doubts the study will have an impact on how women are treated after these surgeries.
"The incidents of Parkinson's disease are low enough that you would have to treat huge numbers of people in order to prevent one case," he said. "If there are any risks, it becomes impractical."
However, Siderowf does think the study could spark a new look at how estrogen protects the brain. "This could lead scientists to develop new therapies for Parkinson's disease," he said.
The study was funded by a grant from the National Institutes of Health. Rocca said he has applied for another grant to continue following the group of women for five more years.
For more on Parkinson's disease, go to the Parkinson's Foundation.