Estrogen May Not Help Alzheimer's, Brain Size, or Memory Feb. 19, 2003 -- There's more evidence that hormones do not protect women from Alzheimer's disease or dementia. Two new studies look at whether estrogen levels affect memory and cognitive ability, and both find there is no link. The studies appear in this month's Archives of Neurology.

It's been a confusing issue, and studies have been inconclusive, writes researcher Leon J. Thal, MD, of the University of California, San Diego School of Medicine.

Previous studies have shown a reduced risk of cognitive decline and Alzheimer's disease, the most common cause of dementia, in women who take estrogen replacement therapy. However, three recent studies have been unable to identify this link. Further adding to the confusion, two studies of women using an estrogen patch -- a form of hormone replacement therapy (HRT) -- reported some improvement in attention and memory.

In this study, Thal reports on 120 postmenopausal women with mild to moderate Alzheimer's disease -- 81 took estrogen, and 39 took a placebo for one year. Researchers measured the women's hormone levels at the beginning of the study, two months later, and one year later. They then compared estrogen levels to seven different cognitive function tests. They wanted to see if the blood levels of estrogen from HRT were associated with improvements in cognition.

The HRT did increase women's hormone levels. However, that did not translate into better cognitive function. When researchers compared the hormone levels with changes in cognitive scores, they found no significant improvements at the two-month or at the twelve-month assessment.

The second study investigates the link between natural estrogen levels and brain size -- specifically, the hippocampus, which is the part of the brain that stores memories. This study does not look at HRT, however, as pointed out by lead researcher Tom den Heijer, MSc, an epidemiologist with the Julius Center for Health Sciences and Primary Care at the University Medical Center in Utrecht, the Netherlands.

His study involved 149 men and 162 women, all over age 60, all with no signs of dementia. Researchers measured the hippocampus of each using magnetic resonance imaging (MRI) as well as their blood levels of estradiol (natural estrogen).

Women with higher estradiol levels had smaller hippocampal size and poorer performance on memory tests, reports den Heijer. In men, there was no relationship between estradiol level and hippocampal volumes. Also, a trend was found in that those with higher estradiol levels had worse memories.

This study does not rule out a possible link between HRT, hippocampal size, and better memory, den Heijer says. He points out that women in this study had lower natural estrogen levels than women on HRT.