Soldiers' study ties head trauma to late-life mental ills

People who have been knocked out or gotten amnesia after a head wound have upped the odds of developing Alzheimer's or other mental impairment later on in life, says new research.

The study, which tracked soldiers in World War II, found that men with the most serious head injuries were four times as likely as their uninjured messmates decades later to develop problems in reading, learning and other areas.

Neurologists before have tried, with mixed results, to find a link between head injury and Alzheimer's disease. Some studies suggest that the first may cause the latter, but others say no.
　　
　　The latest work, which is in the current issue of Neurology, won't settle the matter, experts say. But it does tip the evidence in favor of a connection.

Dr. Richard Havlik, of the National Institute on Aging, and his colleagues at Duke University in North Carolina reviewed the medical records of nearly 1,800 U.S, Navy and Marine Corps troops, 548 of whom had had moderate-to-severe head injuries that required hospital care.

A half century later, the men who'd sustained moderate head wounds -- those that led to unconsciousness or amnesia for less than 24 hours -- were about twice as likely to have Alzheimer's disease or dementia as those who had not, the researchers found.

For those who had suffered particularly severe head trauma -- injuries that lead to blackouts or amnesia lasting more than a day -- the risks of Alzheimer's and dementia quadrupled.

"Once you cause damage even 50 years before, it stays with you," says Havlik. While some research has suggested that recent head trauma is more destructive than that deep in the past, Havlik says his study argues against that conclusion.

"An event longer in the past is more likely to have set off a smoldering inflammation that allowed" the trademark plaques and tangles of Alzheimer's to form in brain cells, he says.

Havlik's group failed to find a link between mild head trauma and eventual cognitive trouble. Previous research has suggested that head trauma in people who carry a gene, APOE-4, associated with Alzheimer's worsened the risk of developing the condition. But Havlik's team couldn't really show that this "synergistic" effect existed, though they did see such a trend in injured men with several copies of the gene.

Ultimately, says Havlik, scientists would like to find ways of treating head injuries soon enough after they occur to prevent long-term brain damage.

That hasn't proved easy. Dr. Deborah Warden, who runs the head injury research program at Walter Reed Army Medical Center, says no one has been able to develop a drug that effectively halts nerve destruction in the wake of head trauma.

A target of particular interest, Warden says, is the period of "diffuse axonal injury," a span of several hours immediately after trauma in which portions of brain cells seem especially vulnerable. "We're looking to be able to intervene in that window," Warden says.

But for now, she says, doctors must rely on other ways of controlling the fallout of such injuries, like monitoring blood pressure.

(From HealthScout)