MONDAY, July 18 (HealthDay News) -- Retired pro football players may face a higher risk of mild cognitive impairment, a potential precursor of Alzheimer's disease, a new study suggests.

"It appears there may be a very high rate of cognitive impairment in these retired football players, compared to the general population in that age range," said lead researcher Christopher Randolph, a neuropsychologist at Loyola Medical University Medical Center in Chicago.

Randolph was scheduled to present the study findings Monday at the Alzheimer's Association International Conference 2011, in Paris.

A second study to be presented at the conference found military veterans who had suffered a traumatic brain injury faced more than twice the risk of developing dementia.

"Traumatic head injury is the best known environmental risk for late-life dementia," said Dr. Sam Gandy, a professor of neurology and psychiatry and associate director of the Mount Sinai Alzheimer's Disease Research Center in New York City, who was not involved with either study.

"Football, soccer, hockey and exposures to IEDs [improvised explosive devices] in Iraq and Afghanistan are all contributing to the incidence of late-life dementia," he added.

The first study found that men who played in the National Football League seem to have a higher risk of developing mild cognitive impairment, which can lead to Alzheimer's disease.

The debate over head injuries among pro football players and the potential for lasting neurological damage has generated a steady stream of headlines in recent years. Last summer, the National Football League issued posters for locker rooms that alerted players to the possible effects of concussions, using words like "depression" and "early onset of dementia," according to The New York Times.

Randolph's study found that among 513 retired players, 35 percent had signs of possible mild cognitive impairment.

Some of the former players were then given more comprehensive tests at the Center for the Study of Retired Athletes at the University of North Carolina in Chapel Hill. The ex-players were compared with 41 similar non-athletes with no cognitive impairment and with 81 people with cognitive impairment.

The former players had similar impairments as those non-athletes with cognitive impairment, but were significantly younger and slightly less impaired, the researchers found.

The findings suggest that repeated head trauma from playing football may lead to earlier onset of degenerative diseases, such as mild cognitive impairment and Alzheimer's, the researchers said.

"However, it would take additional studies to confirm this," Randolph said. "So for now, these studies should be considered very preliminary."

Dr. Ira R. Casson is a former co-chairman of the National Football League's panel on head injuries, and a neurologist at Long Island Jewish Medical Center in New Hyde Park, N.Y. He said he "would be hesitant to draw any major conclusions from the study."

It isn't really known whether NFL players are at a higher risk for dementia, Casson said, adding there isn't a lot of data about the risk of mild cognitive impairment among men.

"If the question is do NFL players have a higher risk of dementia later in life than non-NFL players -- we don't have enough data to answer that yet," he said.

Results of the second study found that traumatic brain injury among older veterans was associated with a nearly threefold increased risk of dementia.

"The data suggest that traumatic brain injury in older veterans may predispose them toward development of symptomatic dementia. And they raise concern about the potential long-term consequences of TBI [traumatic brain injury] in younger veterans," lead researcher Dr. Kristine Yaffe, a professor of psychiatry, neurology and epidemiology at the University of California, San Francisco, said in an Alzheimer's Association news release.

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."

More information

For more on traumatic brain injury, visit the U.S. National Institute of Neurological Disorders and Stroke.