Retired professional football players may have a higher rate than normal of Alzheimer's disease or other memory problems, suggests a preliminary study that provides more fuel for concerns about long-term risk of concussions.
Experts said that the work was not definitive but that it fit in with other studies suggesting a long-term risk from head injuries in sports.
In the new study, 1,063 ex-players were asked if they'd ever been diagnosed with dementia, Alzheimer's disease or other memory-related disease. About 2 percent of the former players ages 30 to 49 said yes. That's 19 times the rate for the same age group in the general population.
For retirees over 50, the rate of about 6 percent was about five times higher.
The study, which has not been published in a peer-reviewed journal, was done for the National Football League by researchers at the University of Michigan.
The results show the topic is worth further study, but they do not prove a link between playing football and later mental troubles, said lead author David Weir.
The study, which covered a variety of health and financial topics, relied on a telephone survey rather than a review of medical records, he noted. The information on memory problems came from a single question taken from earlier population surveys, and its vague wording makes the results hard to interpret, the researchers said. The study was first reported by The New York Times.
"The study was not designed to diagnose or assess dementia," Weir said Wednesday. "The study did not conclude that football causes dementia."
NFL spokesman Greg Aiello agreed and said further study is already under way.
"Memory disorders affect many men and women who never played football or other sports," he wrote in an e-mail. "The survey makes no link between concussions and memory disorders."
Dr. Anthony Alessi, who co-chairs the sports neurology section of the American Academy of Neurology, said smaller studies had indicated repeated concussions or other brain injuries can bring on early dementia.
"This is the way the information is going," said Alessi, who is chief of neurology at the William W. Backus Hospital in Norwich, Conn. "We need to take this study very seriously."
He said the topic should be studied in sports other than football, and that parents and coaches of young athletes with a head injury should let doctors determine when it's safe to play again.
Dr. Scott A. Small, an expert on Alzheimer's and memory at the Columbia University Medical Center in New York, called the new result "intriguing and alarming."
"The most important thing it tells us is that additional studies need to be performed, and I would say, urgently," he said. "This is not a trivial matter."
He noted that studies of brain samples from deceased athletes have established a link between repeated concussions and brain changes somewhat like those seen in Alzheimer's. So that makes the suggestion of the new study more plausible, he said.
Another study of retired professional football players, published in 2005, found that a history of three or more concussions was associated with a boost in risk of mild cognitive impairment after age 50. Kevin Guskiewicz, lead author of that study and director of the Center for the Study of Retired Athletes at the University of North Carolina in Chapel Hill, said the findings of the new study didn't surprise him.
Nor would the study come as a shock to most football players, said the Tennessee Titans' Kevin Mawae, president of the NFL Players Association.
"I think it just reinforces what players already know to be true, at some point in time other people are going to have to face it for fact," he said. "It is what it is."
Any long-term risk of mental impairment is just part of the game, said Brandon Stokley, a receiver on the Denver Broncos, who has a history of concussions.
"Yeah, you always think about things like that," he said. "But again, I'm a football player and that's what I do, so if it happens to me and something's wrong with me, then so be it. This is the life that I chose and I wouldn't trade it for anything."
Sports Writers Arnie Stapleton in Denver and Teresa M. Walker in Nashville contributed to this report.