A study of former NFL players finds they were unusually prone to dying from degenerative brain disease.
It's the latest indication that repeated blows to the head may cause serious trouble later on.
The researchers found the death rate from Alzheimer's, Parkinson's and Lou Gehrig's disease combined was about three times what one would predict from the general population.
The study, which is reported online in the journal Neurology, looked at death certificates.
It drew on a long-running study of more than 3,400 NFL players with at least five playing seasons in the league between 1959 and 1988. Researchers compared their death rates from various causes to those of a comparable group of American men.
The researchers noted the study can't prove the results were caused by football-related concussions.