Study: Head injuries early in life may lead to Alzheimer's disease

WASHINGTON (Reuters) -- Veterans who had serious head injuries decades ago now have a higher risk of Alzheimer's disease, a finding that suggests serious blows to the head may somehow cause delayed brain damage, researchers said Monday.

The more severe the head injury, the greater the risk of developing Alzheimer's, teams at the U.S. National Institute on Aging (NIA) and Duke University in North Carolina found.

The researchers said they do not know just what, biologically, is happening over the 50 years between injury and disease in the men, but said their study shows that Alzheimer's is a long-term, progressive condition.

"We found that head injury in early adult life was associated with increased risk of Alzheimer's disease and dementia in late life, and that this risk increased with the severity of the injury," the researchers wrote in their report, published in Tuesday's issue of the journal Neurology.

"Understanding how head injury and other Alzheimer's disease risk factors begin their destructive work early in life may ultimately lead to finding ways to interrupt the disease process early on," Brenda Plassman of Duke University, who helped lead the study, said.

The study does not show that injuries directly cause Alzheimer's, Dr. Richard Havlik of the NIA cautioned.

"While we may not fully understand what's going on, as a practical matter, it may be one more reason to wear that bike helmet instead of keeping it in a closet," he said. But then he added that the injuries the veterans suffered may have been very different from today's common head injuries, which often come during sports activities.

Havlik, Plassman and colleagues looked at the military medical records of male Navy and Marine World War II veterans who were hospitalized with a diagnosis of head injury or an unrelated condition. They used current Veteran's Affairs medical records to track down 548 veterans who had suffered a head injury and 1,228 veterans who had not.

They separated out those with mild injury, involving loss of consciousness or amnesia for less than 30 minutes with no skull fracture, moderate injury with loss of consciousness or amnesia for more than 30 minutes but less than 24 hours, or a skull fracture, and severe injury with loss of consciousness or amnesia for 24 or more hours.

The scientists then tested volunteers to see which of the veterans had Alzheimer's.

The risk of Alzheimer's and other forms of dementia was doubled in the men with moderate head injury, and it was four times greater in those who had severe head injury.

Havlik said inflammation could be involved.

"Clinical studies show that if somebody is in an acute accident and dies within a few days, there is a lot of damage to the brain," he said.

"There is evidence of amyloid, the building block of the famous plaques (that define Alzheimer's and which are found in the brains of Alzheimer's patients). Pathologists are seeing these within a few days or weeks of head injury."

Scientists believe the amyloid plaques are evidence of the brain trying to repair itself.

When brain cells are damaged, they send out many different chemical signals. For unknown reasons, some of these signals cause surrounding healthy brain cells to die.

Studies have also suggested that people who took anti-inflammatory drugs long-term, such as arthritis sufferers, have a lower risk of Alzheimer's.

Havlik said the study got around earlier problems of previous studies, which showed that people could not remember head injuries they got decades ago, or which were based on interviews with family members.

But he said other, unknown factors may have had a role to play. "We are talking about 50 years here," he said.

Copyright 2000 Reuters. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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