The angiotensin hypothesis makes sense, Lipton said, because improved blood flow to the brain helps nerve cells and reduces formation of Alzheimer's-related amyloid protein.
But there have been a number of observational studies implicating various molecules, including estrogens, in dementia, he said. "The sequence is that when you do the randomized trial, you don't get the same effect," Lipton said.
On the other hand, such randomized trials usually include people who are close to having Alzheimer's disease, and "it could be different if you gave the drugs earlier," Lipton said.
The U.S. Food and Drug Administration has more on blood pressure medications.
SOURCES: Benjamin Wolozin, M.D., professor, pharmacology and neurology, Boston University School of Medicine, Boston; Richard B. Lipton, M.D., professor and vice chairman, neurology, Albert Einstein College of Medicine, New York City; Jan. 13, 2010, BMJ, online