A long term, unique study by scientists in America has found that estrogen may protect the brains of premenopausal women from cognitive impairment and even dementia in later life.
The study is published in the August 29th online edition of Neurology and is the work of researchers at the Mayo Clinic in Rochester, Minnesota.
Dr Walter Rocca, neurologist and epidemiologist at the Mayo Clinic and lead author of the study, and colleagues, found that women who removed one or both of their ovaries before the menopause and did not take estrogen were more likely to have neurological impairment (eg parkinsonism, a range of neurodegenerative disorders, including Parkinson’s Disease), and even dementia later in life than either women who kept their ovaries or premenopausal women who removed both ovaries but took estrogen until the age of 50.
Nearly 3,000 women were followed for over 30 years and interviewed. The study is thought to be the largest of its kind and the first to provide robust population based evidence that estrogen plays an important role in protecting the brains of younger women.
As Rocca explained:
“This study is one of the first to obtain large-scale data about neurological diseases in women who had their ovaries removed.”
“Our findings will contribute to a better understanding of the advantages and disadvantages of removing the ovaries in young women,” he added.
He suggested that the study also reveals there is a “window of therapeutic opportunity” for estrogen replacement therapy for women who undergo ovary removal before the age of 50.
“This window of opportunity is before the approximate age of naturally occurring menopause, when the benefits of neuroprotection are likely to outweigh the risks of side effects of estrogen therapy,” said Rocca.
By side effects Rocca is referring to other research that suggests when estrogen therapy is started after around the age of 60 to 65, it increases the risk of heart problems, stroke, cognitive impairment and dementia.
The Mayo study also found that the risk of adverse neurological effects went up as the age of the women who underwent ovary removal went down. In other words, the younger the woman was when she underwent ovary removal, regardless of the reason, the greater the risk of adverse neurological effects later in life (if she did not take estrogen).
And, curiously, the risk was the same even if the women only had one ovary removed, said Rocca.
According to the researchers, the study has important clinical implications for women looking at options for ovary removal and post operative estrogen therapy.
A Mayo Clinic gynecological and obstetrical surgeon, Dr Bobbie Gostout put it like this:
“In every medical or surgical decision there is a trade-off between risks and benefits.”
“Therefore, a woman considering ovary removal should discuss these findings with her physician prior to the surgery to consider the long-term implications and the possible strategies for estrogen treatment following the surgery,” suggested Gostout.
It is important in the light of these findings that women make informed choices with the help of counselling tailored to her needs and situation, said Gostout:
“When oophorectomy (ovary removal) is indicated in a young woman, it is important to carefully educate that patient regarding estrogen replacement. Unless clear contraindications are present, most women should be advised to take estrogen therapy until approximately age 50,” she advised.
The researchers used the Rochester Epidemiology Project to find nearly 1,500 women resident in Olmsted County, Minnesota, who had had one or both ovaries removed between 1950 and 1987.
They age-matched the women to an equal number of women who did not undergo ovary removal. They interviewed both groups of women (or their relatives) and participants also completed a cognitive test over the telephone (if the woman was no longer alive a relative was interviewed).
They then compared the risk of cognitive impairment or dementia between the two groups.
The authors concluded that:
“Both unilateral and bilateral oophorectomy performed prior to menopause may be associated with an increased risk of parkinsonism and the effect may be age-dependent. However, our findings await independent replication.”
The Rochester Epidemiology Project, which is based at the Mayo Clinic, started collecting medical records in 1935, and is now one of the largest long term patient medical record databases in the world.
Many women have one or more ovaries removed for various reasons such as a cyst or ovarian cancer, or endometriosis.
The US Centers for Disease Control and Prevention, CDC, estimates nearly half a million American women underwent this procedure in 2004.
The study was supported by grants from the National Institutes of Health (NIH).
“Increased risk of parkinsonism in women who underwent oophorectomy before menopause.”
W. A. Rocca, J. H. Bower, D. M. Maraganore, J. E. Ahlskog, B. R. Grossardt, M. de Andrade, and L. J. Melton III.
Neurology Published online August 29, 2007.
doi:10.1212/01.wnl.0000280573.30975.6a
Written by: Catharine Paddock