(From: MedPage Today, Published July 28, 2008)

Hormone replacement therapy (HRT) at midlife has been associated with reduced women’s risk of developing dementia in old age, researchers reported here. But, they added, those women who started hormones age 70 or older increased their risk of Alzheimer’s disease.

Compared with controls and after adjusting for other risk factors, women who only used hormone replacement at midlife had a decreased risk of dementia by about 24% versus a 46% increase in risk among women who only took hormones late in life (P=0.03), said Rachel A. Whitmer, Ph.D., of Kaiser Permanente Division of Researcher in Oakland, Calif., and colleagues.

“The findings appear to confirm the ‘window of opportunity theory,” Dr. Whitmer said while reporting an analysis of data form 5,553 women at the International Conference on Alzheimer’s Disease.More…

In the Kaiser study, hormone therapy was evaluated by surveys conducted from 1964 to 1973, when the women were age 40 to 55 and evaluated by tracking the Kaiser pharmaceutical database when the women were age 70 to 80. The researchers then correlated hormone therapy use with diagnoses of dementia — including vascular dementia — and Alzheimer’s disease from medical records entries from Jan. 1, 1999 through Nov. 15, 2007, she said. Findings were adjusted for a number of risk factors including hypertension, hyperlipidemia, diabetes, and stroke. The mean age of women at the time of the mid-life survey was 49. Sixteen percent of the women (889) used hormone replacement only in midlife, 727 used at both time points, and 939 or 17% only used hormone replacement in old age. Most of the women-2,949-did not use hormone therapy at either time point.

During follow-up 1,524 women were diagnosed with dementia during the follow-up period. Dr. Whitmer said the study had a number of limitations, including a lack of data on duration of hormone use at midlife, as well as a lack of data on dose and type of hormones used during the midlife period.

Nonetheless, she concluded that it would be impractical to conduct a randomized controlled trial that followed women for 30 years or more to investigate the possibility that hormone therapy was neuroprotective. “But we can do trials like this to look at cognitive function or cognitive domains, and trials like this with very detailed data about midlife could help us answer these questions,” she said.

(Source reference: Whitmer RA et al “Postmenopausal hormone therapy in mid-life versus late-life and risk of dementia” ICAD 2008)

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