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Hormone Replacement Timing May Improve Chances of Avoiding Dementia: Presented at ICAD

By Ed Susman

CHICAGO -- July 28, 2008 -- Women who take hormone replacement therapy (HRT) during midlife or close to the time of menopause appear to have a lower risk of developing dementia compared with women who take this therapy later in life, researchers reported here at the 2008 International Conference on Alzheimer's Disease (ICAD).

"However, women who started hormones at 70 years or older had a higher risk of Alzheimer's disease," said Rachel A. Whitmer, PhD, Division of Research, Kaiser Permanente, Oakland, California.

Dr. Whitmer discussed the findings on 5,553 women in the Kaiser Permanente of North Carolina database in an oral presentation on July 27.

After adjusting for other risk factors, women who used HRT at midlife decreased their risk of dementia by about 24% compared with women who did not take any HRT, while women who took hormones only late in life had a 46% increase in risk (P = .03).

"The findings appear to confirm the 'window of opportunity' theory," Dr. Whitmer said. "The theory assumes there is a time when HRT works to the benefit of the patients and other times when this treatment may be detrimental."

The researchers evaluated HRT through surveys conducted from 1964 to 1973 when the women were 40 to 55 years and by tracking the Kaiser pharmaceutical database when the women were 70 to 80 years. The researchers then correlated the women's use of HRT with diagnoses of dementia -- including vascular dementia -- and Alzheimer's disease from medical record entries from January 1, 1999, through November 15, 2007.

"They adjusted the results for possible confounder effects of risk factors such as hypertension, hyperlipidaemia, diabetes, and stroke," Dr. Whitmer said.

The mean age of women at the time of the midlife survey was 49 years. Sixteen percent of the women used HRT midlife only, 17% used HRT in old age only, and 13% used it at both time points. Most of the women (2,949) did not use hormone therapy at any time point.

During follow-up, 1,524 women were diagnosed with dementia.

Dr. Whitmer said the study had a number of limitations, including a lack of data on duration of HRT use at midlife as well as a lack of data on dose and type of hormones used during the midlife period.

The trial was supported by the National Institutes of Health.

[Presentation title: Postmenopausal Hormone Therapy in Mid-Life Versus Late-Life and Risk of Dementia. Abstract O1-05-03]

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