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Alzheimer's Risk Changes With Timing Of Hormone Therapy

New research from the US suggests that use of hormone therapy may affect women's risk for developing Alzheimer's disease: those who start it within five years of menopause may experience a lower risk, and those who start it later may experience a raised risk for the neurodegenerative disease.

Peter P. Zandi of Johns Hopkins University in Baltimore and colleagues write about their findings in a paper that was published online in the journal Neurology on Wednesday.

In their background information, the authors describe how different studies have come to different conclusions about whether hormone therapy lowers or raises women's risk for Alzheimer's disease.

They write that observational studies (the sort that follows a group over a period of time), tend to suggest hormone therapy reduces the risk, whereas clinical trials (that test the effect of a drug against a control like a placebo), suggest it raises it.

So they decided to investigate whether timing or type of hormone therapy made a difference.

In a press statement, Zandi explains what they found:

"Our results suggest that there may be a critical window near menopause where hormone therapy may possibly be beneficial."

"On the other hand, if started later in life, hormone therapy could be associated with an increased risk of developing Alzheimer's disease," he adds. What the Researchers Did For the study, Zandi and colleagues followed 1,768 women aged 65 and older for 11 years.

The data included a history of the women's use of hormone therapy and the date when their menopause started. Of the participants, 1,105 had used hormone therapy, either estrogen alone or combined with progestin.

Over the course of the follow-up, 176 women developed Alzheimer's disease dementia. Of these, 87 were among the 1,105 who used hormone therapy, while 89 were among the 663 others who did not. What They Found After statistical analysis, the figures showed that women who started hormone therapy within five years of menopause onset had a 30% lower risk for Alzheimer's dementia compared with those who had not used it.

Among other hormone therapy users who had started hormone therapy more than five years after menopause onset, the risk of Alzheimer's dementia was unchanged, except that a higher risk was seen in women who started a combined estrogen and progestin therapy when they were at least 65 years old.

The authors conclude:

"Association of HT [hormone therapy] use and risk of AD [Alzheimer's disease] may depend on timing of use. Although possibly beneficial if taken during a critical window near menopause, HT (especially opposed compounds) initiated in later life may be associated with increased risk." Implications: Too Early for Clinical Recommendations The authors recommend further studies should now be done to look more closely at the link between timing of hormone therapy use and risk for Alzheimer's.

In an accompanying editorial Victor Henderson of Stanford University in California, and Fellow of the American Academy of Neurology, agrees:

"While this well-designed study supports the possibility that short-term hormone use may reduce the risk of Alzheimer's disease, more research is needed before we can make new clinical recommendations for women and their use of hormone therapy."

Grants from the National Institute on Aging helped fund the study.

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