Delaying dementia: drugs that fail as cures might still prevent Alzheimer's disease.

Alzheimer's disease extinguishes the mind and body through a vicious progression from mental lapses, memory loss, and dementia to the final failure of the brain to support survival. Medical efforts to abate the disorders development after symptoms arise have yielded discouraging results. Once unmistakable traits of Alzheimer's emerge, it seems, the mind is at the disease's scant mercy. None of the five drugs with U.S. government approval for Alzheimer's, including the latest, called memantine or Namenda, does more than slow or temporarily stop mental deterioration.

Meanwhile, increases in life expectancy and a burgeoning population of elderly people are expanding the scope of the Alzheimer's problem. While some 4 million people in the United States have the disease now, 13 million could have it in 2050.

To avert the rising fide of Alzheimer's in the absence of a cure, many researchers are looking to drugs and nutrients that could prevent or at least delay the disease's onset. Marginally delaying the average onset of Alzheimer's could take a substantial bite out of the epidemic, says Carl W. Cotman of the University of California, Irvine. He estimates that pushing back initial symptoms by 5 years in the average Alzheimer's victim would halve the number of new cases that appear yearly in the U.S. population.

Recent advances in brain imaging have increased the reliability of diagnosing full-blown Alzheimer's in a living person. But the brain's biology begins to go haywire long before symptoms of serious mental decline or outright Alzheimer's become evident. And it's still a challenge to distinguish someone on track to developing Alzheimer's from someone who is aging normally--much less treating that individual to slow or stop the disease process.

Epidemiological observations have generated promising leads to preventive treatments, including…