Yaffe's team collected data on nearly 282,000 U.S. veterans aged 55 and older who received medical care through the Veterans Health Administration from 1997 through 2000. None of the veterans had dementia at the start of the study.
The researchers found that among veterans who had suffered a traumatic brain injury, 15.3 percent developed dementia, compared with 6.8 veterans who didn't suffer such an injury.
"This issue is important because traumatic brain injury is very common," said Yaffe, who is also director of the Memory Disorders Program at the San Francisco VA Medical Center. "About 1.7 million people experience a traumatic brain injury each year in the United States, primarily due to falls and car crashes. Traumatic brain injury is also referred to as the 'signature wound' of the conflicts in Iraq and Afghanistan, where traumatic brain injury accounts for 22 percent of casualties overall and 59 percent of blast-related injuries."
Gandy said these new studies could have major implications for high school and college athletes. "Just last year, the first college student committed suicide from chronic traumatic encephalopathy, which he must have developed during high school football," he noted.
Chronic traumatic encephalopathy is a progressive, degenerative disease in people who have had multiple concussions or other head injuries.
Dr. Gail L. Rosseau, a neurologist at the Northshore University Health System in suburban Chicago and spokeswoman for the American Association of Neurological Surgeons, said it's not clear whether concussions lead directly to dementia.
"We don't know the answer," she said. "It's an area of very aggressive research, but we just don't know enough yet. But the implications are enormous because of the huge numbers of adults and children who are involved in sports."
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