Former NFL players have been diagnosed with Alzheimer's disease or other memory-related conditions at rates much higher than the national population, according to a study commissioned by the league, The New York Times reported.
The phone survey of 1,063 former players found that 6.1 percent of players aged 50 and older reported that they had received a dementia-related diagnosis. That's five times higher than the cited national average of 1.2 percent, according to the report.
And players ages 30 through 49 reported dementia-related diagnoses at a rate of 1.9 percent -- 19 times the national average of 0.1 percent, according to the report.
Dr. Julian Bailes, the chairman of the department of neurosurgery at the West Virginia University School of Medicine whose own research suggested similar links between football head injuries and dementia, called the latest results "a game-changer," according to the Times.
"They always say, 'We're going to do our own studies.' And now they have," said Bailes, a former team doctor for the Pittsburgh Steelers, according to the report.
A summary of the study, which was conducted by a telephone survey of former players in 2008, was sent to league officials earlier this month, according to the report. Of the 1,625 former players selected at random, 1,063 took part in the survey, which was conducted by the University of Michigan's Institute for Social Research. It has yet to be peer-reviewed.
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 not designed to diagnose or assess dementia," Weir said Wednesday. "The study did not conclude that football causes dementia."
In an e-mail, NFL spokesman Greg Aiello said the study gave the league something to look at as it affects its players. "There are thousands of retired players who do not have memory problems," he said, according to the report.
"Memory disorders affect many people who never played football or other sports," Aiello said, according to the Times. "We are trying to understand it as it relates to our retired players."
In a statement released Wednesday, the NFL noted that the survey did not diagnose dementia in players, "but relied on self-reporting or family proxy reporting on a retired player's memory" and added that memory diseases are rare in both the general population and among NFL retirees. The league also noted the study did not draw a link between concussions and memory disorders.
Dr. Ira Casson, a co-chairman of the league's concussions committee, said a follow-up to the Michigan study is needed, according to the Times.
"What I take from this report is there's a need for further studies to see whether or not this finding is going to pan out, if it's really there or not," Casson said, according to the report. "I can see that the respondents believe they have been diagnosed. But the next step is to determine whether that is so."
The NFL is conducting its own study of 120 retired players, with Casson conducting the neurological examinations, according to the Times. The results of that study are expected within a few years.
Information from The Associated Press was used in this report.