MONDAY, July 24, 2006 (HealthDay News) -- Do hormones affect men's risk for Alzheimer's disease?
New research suggests that relatively high blood levels of estrogen might boost the risk for men, but that levels of circulating testosterone didn't seem to matter.
Both findings raised eyebrows among experts.
"What makes it interesting is that a lot of attention has been paid to estrogen levels in women," said Dr. Barbara Snider, an assistant professor of neurology at Washington University in St. Louis. "Studies have indicated that women who took estrogen replacement therapy might have an increased risk. Now they're looking at estrogen levels in men."
Although it's typically seen as a "female" hormone, men also produce small amounts of estrogen throughout their lives.
Of course, testosterone is found much more abundantly in men than women. But the finding that testosterone had no effect on Alzheimer's risk "conflicts with at least two large epidemiological trials," both of which found higher risk of dementia in men with low circulating testosterone, noted Dr. Jeremiah Kelly, an associate professor of medicine at Rush Alzheimer's Disease Center in Chicago.
"That's puzzling," Kelley said.
As reported in the August issue of the Annals of Neurology, a research team from the Netherlands and the U.S. National Institute on Aging took blood samples from nearly 3,000 Japanese-American men, aged 70 to 91, living in Hawaii between 1991 and 1993. They measured levels of testosterone and estradiol, the major form of estrogen.
Over the next decade, 134 of the men developed Alzheimer's disease and 44 developed another form of dementia.
High levels of estradiol were associated with an increased incidence of dementia, but the team noted no association between cognitive decline and levels of testosterone.
"One possibility is that the population they looked at is not a representative population," Kelly said. Previous studies have shown that older men with higher levels of testosterone scored better on tests of executive function and attention, he said.
It's also possible that the tests used in the study "were not broad enough to assess all the changes in cognitive function," Kelly said.
Both Kelly and Snider also noted that the findings were based on blood tests alone. "They're looking in the blood, but what matters is the level in the brain," Snider said. According to Kelly, the relationship between blood levels and brain levels of the hormones remains "an unanswered question."
"We don't understand how these hormones interact with Alzheimer's disease," Snider said. "Hopefully what this study will do is spur studies to look at the role of estrogen in men."
Find out much more on dementia at the Alzheimer's Association.