New Science Sheds Light on the Cause of Alzheimer’s Disease

En español | New research appears to upend our current scientific understanding of the causes of Alzheimer’s disease, and may lead to a whole new approach to finding a cure for the devastating dementia. The new theory gaining traction in the scientific community is that in Alzheimer’s the brain is destroyed not by sticky plaques — long held to be the culprit — but by floating clumps of protein. In fact, the sticky plaques that coat the brain cells of those with Alzheimer’s may be the body’s way of protecting against these deadly clumps — the way an oyster forms a pearl to protect against an irritating grain of sand, according to one researcher. 

Sign up for the AARP Health Newsletter.
 

Floating clumps of protein in the brain, not sticky plaques, may be behind Alzheimer's disease. — PASIEKA/Science Photo Library/Getty Images 

For the last 20 years, following the prevailing theory that sticky plaques cause Alzheimer’s disease, drug developers have been targeting that plaque in their search for a cure. 

But experiments in mice and rats may prove to be the tipping point that takes that research in a new direction. Many scientists now believe the free-floating clumps of protein, rather than the sticky plaques, are the main players in the rogue process that attacks the brain.

“Plaques are no longer where the action is,” says Sam Gandy, M.D., of the Alzheimer’s Disease Research Center at Mount Sinai School of Medicine in New York. 

Gandy’s work builds on several years of research that has been moving science toward this new theory. And if the theory is correct, then drugs that target plaques — as many of the most promising medications have done in the past few years — won’t help people who have the disease. It could even make them worse. Gandy’s work with specially engineered mice, which developed Alzheimer’s though they had only clumps of the amyloid beta protein, and no plaques in their brains, “is the final experiment that’s making the whole field turn around,” says Andrew Dillin of the Salk Institute of California and the Howard Hughes Medical Institute. 

While the development is exciting, William Thies, the Alzheimer’s Association’s chief medical officer, cautions that the leap from mice to men is a long one and that Gandy’s experiments need to be duplicated by other scientists in other labs before drug companies invest billions of dollars to create new medicines that target these clumps of proteins. 

Still, this emerging science is especially important in light of statistics from the Alzheimer’s Association that say the number of Americans 65 and older who have the disease is likely to increase from more than 5 million today to 13 million 40 years from now as large numbers of boomers age. Economic costs are expected to rise from $183 billion this year to more than $1 trillion by 2050. As part of the National Alzheimer’s Project Act, the government recently announced a goal of finding a way to prevent and treat Alzheimer’s disease by 2025. President Obama signed the law January 2011 and a final draft of a multi-agency plan is due to the Department of Health and Human Services in the spring.

A tangled web 

Gandy’s study looked at the most basic science of the disease in a very different way. 

“Alzheimer’s seems to be caused by the buildup in the brain of clumps of material that are formed by the breakdown of protein,” Gandy says.

Next: What plays a role in the progression of Alzheimer's? »