"Typically, head injury is found to roughly double the risk for developing dementia," added Cole, who's also associate director of the Mary S. Easton Center for Alzheimer's Disease Research. "But if victims also have the most common genetic risk factor [ApoE4], present in about 20 percent of the population and which similarly increases risk by itself, the combined risk is much higher, around tenfold or more. Animal model studies show this relationship is probably causal because head injury can really speed Alzheimer's pathology. All of this makes it pretty clear to experts studying AD [Alzheimer's disease] that in individuals with some preexisting genetic risk for Alzheimer's, repeated head injury should be expected to make dementia much more likely."
For the NFL survey, the Michigan researchers contacted 1,063 retired players by phone late last year. The players, who had to have played at least three seasons to qualify for the survey, were asked a series of questions on a series of topics, including questions on health, financial well-being and satisfaction with life. Most of the questions came from the standard National Health Interview Survey. That way, answers could be compared to previously collected data from the general population. In some cases, a player's wife answered the questions.
The Michigan researchers found that, among players aged 50 and older, 6.1 percent of them said they had received a dementia-related diagnosis -- five times higher than the national average of 1.2 percent.
Players between the ages of 30 and 49 had a dementia-related diagnosis rate of 1.9 percent -- 19 times higher than the national average of 0.1 percent, according to the survey.
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