Probing Question: Can Alzheimer's disease be prevented?

two depictions of brains
NIH

Top: Normal brain; Bottom: Alzheimer's Diseased brain

Most of us have had the experience of forgetting where we've parked our car or have struggled to recall an acquaintance's name. But once we hit our 50s, says James R. Connor, these incidents might cause us to worry that we're showing early signs of Alzheimer's disease.

Fortunately, that's not usually the case, says Connor, distinguished professor of neurosurgery at Penn State College of Medicine. "If forgetting something now and then was a good indicator of dementia, we'd all be in trouble," he adds with a laugh.

This dreaded condition was first classified as a disease one hundred years ago by German psychiatrist Alois Alzheimer and is the "leading cause of dementia in the elderly," explains Connor. In fact, four million Americans now suffer from this progressive disease, including up to 50 percent of seniors over age 85 and up to 15 percent of those over 65.

The aging of the Baby Boomers will swell those numbers in the coming years. "At the present time, Alzheimer's Disease (AD) costs the nation 100 billion dollars a year, with an average $174,000 lifetime cost per patient," Connor says. "By the year 2050, there will be an estimated fourteen million Americans with the disease."

Is it possible to prevent Alzheimer's? For those who already have signs of persistent memory decline, there are some neurosurgical procedures and therapeutic drugs available that may help slow the disease's ravages, Connor notes. But for the millions of "worried well," science has not yet found any definitive ways to prevent the disease.

Although recent research suggests that genes may play a role in contracting the disease, "the number one risk factor for Alzheimer's is aging," says Connor. "You have to live long enough to develop this disease," which researchers believe to be caused, in part, by a sticky protein called amyloid that makes up plaque" that accumulates in the brain. Another change in the brain in AD is "neurofibrillary tangles"—protein threads that strangle cells and disrupt the transmission of their signals. The strangulation eventually kills nerve cells. "If we have a computer with cables that are broken and tangled, it won't work right, and it's the same with our brains," says Connor.

Scientists speculate that the protein coatings and tangles within the brain could be the body's inflammatory response to long-term toxin exposure, as well as damage from "free radicals," unstable molecules that attack and harm the body's cells by stealing their electrons through a process called oxidation.

Although some studies suggest that anti-inflammatory drugs (including common painkillers such as ibuprofen and naproxen) may help to limit amyloid plaques, "we need to proceed with caution in this area," Connor believes. One paradox of the disease, he says, is that "there may be a positive function to the plaques. They may be the body's way of sealing off leaky blood vessels in the brain."

Many researchers believe that metals (chiefly iron, copper, and zinc) may play a role in Alzheimer's, since these substances are abundant within the folds of plaque in diseased brains. When free radicals bump into metal atoms in the body, they unleash a chain reaction that can wreak havoc on healthy cells, prematurely aging them and potentially leading to a variety of serious health conditions. MRIs and autopsies of patients with advanced Alzheimer's often reveal massive iron accumulation, Connor notes.

Although excess metals may damage the brain, he adds, another paradox is that small amounts of these micronutrients are absolutely essential to healthy brain function.

Research on the exact link between metals and memory processing is inconclusive at this point. "Is there too much copper or too little in the brains of AD patients? Studies are unclear," Connor remarks. So, too, is the role of zinc, he adds. Though there's high zinc content in the healthy hippocampus—the part of the brain responsible for short-term memory—"the jury is still out on the connection, so there's no reason to recommend zinc supplements at this point. Too much might cause a problem as well. It's all about the right balance."

Nor should you completely avoid dietary iron or copper, suggests Connor, although some physicians recommend "decreasing your iron burden" through occasional blood donation, particularly for men and post-menopausal women, who are at higher risk for accumulating iron and for developing neurodegenerative diseases.

Other recommendations made by some physicians (particularly for patients noticing subtle cognitive decline) include taking antioxidants such as vitamins E and C, and making dietary changes.

"Remember," says Connor, "that if you flip the statistics, at least half of those over 85 don't have Alzheimer's. In addition to studying those with the disease, we're also studying seniors with good short-term memories, looking for predictors of healthy neurocognitive aging."

James R. Connor, Ph.D., is professor and vice chair in the department of neurosurgery at the Penn State College of Medicine, jrc3@psu.edu. This feature is based on a lecture given by Connor on January 27 at University Park as the first of the 2007 Penn State Lectures on the Frontiers of Science.

Last Updated February 05, 2007