WEDNESDAY, Oct. 24 (HealthDay News) -- It is said that timing is everything. When it comes to taking hormone replacement therapy, that may indeed be true.
A new study has found that taking hormone replacement therapy within five years of menopause may reduce the risk of developing Alzheimer's disease by 30 percent compared to women who have not used hormone therapy.
The researchers set out to better understand why some previous studies had shown hormones were effective in reducing Alzheimer's risk while others had not.
The Women's Health Initiative Memory Study, a large, multicenter trial, was stopped prematurely in 2002 due to concerns that the hormones might be raising the risks of cardiovascular disease, cancer and dementia.
"The Women's Health study put a cloud over doing further research," said Peter Zandi, author of the latest study and an associate professor at Johns Hopkins University Bloomberg School of Public Health, in Baltimore. "But there was still some mystery: Why were those results so different?"
The new study, performed by a different team of researchers, expanded the previous research by including up to seven years of additional follow-up and more detailed data on the duration, type and timing of hormone therapy.
The new research was published online Oct. 24 in the journal Neurology.
"We found there is likely a critical window after menopause when hormone therapy may be beneficial," Zandi said. "But if started later after menopause, hormones may actually increase the risk of developing Alzheimer's."
Why might that timing be important?
"We don't really know, but we have some ideas," Zandi said. "Around menopause there's a sudden decline in endogenous estrogens, and that may have some provocative effect. Alzheimer's is a chronic disease that most likely has roots in middle age, or earlier." Endogenous es
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