July 19, 2011 (Paris) -- One in three retired NFL football players appear to have mild cognitive impairment (MCI), researchers report.
"Cognitive impairment seems to be more prevalent in retired American football players than in the general population that age, where you do not see rates anywhere approaching 35%," says study head Christopher Randolph, PhD, clinical professor of neurology at Loyola University Medical Center in Chicago.
The findings are preliminary. And not every football player is destined to develop memory loss or other cognitive problems, says William Thies, PhD, scientific director of the Alzheimer's Association.
Also, current players may be at less risk than in the past, he tells WebMD. NFL rules now require that players with symptoms of a concussion be cleared by a neurologist before they can return to play.
But the findings suggest that mild, repeated blows to the head -- like the kind suffered by many players during their careers -- may predispose people to dementia. That challenges the view that only moderate or severe brain injuries that render one unconscious pose a danger.
The findings were presented here at the Alzheimer's Association International Conference.
About 1.7 million Americans suffer brain injuries each year, according to the CDC.
Head injuries among football players have grabbed headlines in recent months. Earlier this month, Baltimore Colts tight end John Mackey died after being diagnosed with dementia. The autopsy of former Chicago Bears safety Dave Duerson, who killed himself in February at age 50, showed evidence of traumatic brain injury.
The new findings come from a follow-up study to the researchers' 2005 study showing that retired football players appeared to be at increased risk for mild cognitive impairment and Alzheimer's disease.
The researchers hypothesized at the time that "this might be due to repeated concussions or the cumulative effects of repetitive head trauma," Randolph tells WebMD.
Other recent studies have shown that the average college football player incurs more than 1,300 blows forceful enough to lead to permanent injury every season, he says.
The new study involved 633 retired NFL players -- age 50 or older -- who responded to a survey about their general health in 2001 and a second survey focusing on memory issues in 2008.