The researchers found that higher leptin levels were associated with a lower incidence of Alzheimer's and all other forms of dementia. The 25 percent of participants with the lowest leptin levels had a 25 percent risk of developing Alzheimer's over a 12-year period; the incidence was only 6 percent for those with the highest leptin levels. And lower leptin levels were associated with a greater decrease in total brain size.
It's not now possible to say what leptin might be doing to help the aging brain, and "we're not recommending that anyone get leptin or increase leptin levels," Seshadri said. For starters, animal studies are needed to better determine possible risks as well as benefits, she said.
"Other cohort studies are needed to substantiate our findings," Seshadri said. Because the Framingham population is overwhelming white, "we need to look at people who are non-Caucasian," she said. "We also need to look at younger people, in their 50s or 60s."
Another report in the same issue of the journal described disappointing results in a trial of a once-promising drug to prevent Alzheimer's disease.
The drug, tarenflurbil, was designed to reduce production of amyloid, a protein that forms plaques in the brains of people with Alzheimer's disease. The study of 1,684 people who began taking the drug in the early stages of Alzheimer's disease showed no benefit, the report said.
But the anti-amyloid strategy is far from dead, said Dr. Lon S. Schneider, a professor of psychiatry, neurology and gerontology at the University of Southern California, and a co-author of the journal report.
"This was one of the early anti-amyloid approaches," Schneider said. "It was a definitive trial showing definitely that there was nothing here. But it doesn't mean that anti-amyloid strategies will fail, just that this drug isn't effective."
A number of other therapies that target amyloid are now in hu
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