Thwarting Major Killers/Preventing Good Brains from Going Bad; The Quest to Beat Aging; Scientific American Presents; by Mia Schmiedeskamp; 8 Page(s)

It's hard to believe now, but 30 years ago the average layman and the average doctor thought that "senility" was the result of either normal aging or hardening of the arteries. "What do you expect from an old person?" people would say. Mercifully, science has enlightened this rather Dickensian view. Today we may be close to understanding what causes the major neurological diseases of old age, which ravage mental and physical function-the very stuff of life-and in their extreme form can kill.

But that does not mean we've found cures for the four million Americans suffering from Alzheimer's disease and the one million with Parkinson's. The numbers could swell fourfold by 2040 as baby boomers reach old age. Legions of us worship at the temples of Physical Fitness and Cooking Light, in an attempt to ensure strong bodies at retirement. But what can we do when it's our brains that betray us?