Researchers have found the first gene mutation that protects against Alzheimer's disease, a finding that supports a now-controversial theory about the cause of the disease and that could eventually lead to the development of new drugs to treat the disorder. The gene mutation also protects against normal dementia of aging, suggesting that the two diseases have mechanisms in common.
Alzheimer's affects an estimated 5.4 million Americans, and the prevalence increases with age: 13% of those older than 65 and 45% of those over the age of 85 have it. The disease is characterized by the buildup in the brain of particles called amyloid plaque, which are composed of a protein called amyloid beta. Amyloid beta is produced by the breakdown of a larger protein called amyloid precursor protein, or APP. Researchers have so far identified at least two dozen variants of APP that produce early-onset Alzheimer's disease in people younger than 65. The new variant, reported online Wednesday in the journal Nature, is the first that protects against Alzheimer's.
The idea that breakdown of APP causes Alzheimer's has led many pharmaceutical companies to search for drugs that could delay Alzheimer's by inhibiting the breakdown. Unfortunately, clinical trials of those drugs have been almost uniformly unsuccessful, leading many critics to doubt the theory. The new findings, however, tend to place it on firmer ground.