Researchers from the National Institute for Occupational Safety and Health studied 3,439 former NFL players, splitting them into two groups. The "speed" group consisted of quarterbacks, running backs, wide receivers, and linebackers, players, more likely to be involved in hard hits, resulting in a traumatic brain injury, like a concussion. The "non-speed" group was made up of offensive and defensive lineman.
Players in the "speed" group were three times more likely to die from a neuro-degenerative disease like Alzheimer's or ALS, than "non-speed" position players.
"These results are consistent with recent studies that suggest an increased risk of neuro-degenerative disease among football players," said study author Everett J. Lehman, MS. "Although our study looked at causes of death from Alzheimer's disease and ALS as shown on death certificates, research now suggests that chronic traumatic encephalopathy (CTE) may have been the true primary or secondary factor in some of these deaths.
A brain autopsy is necessary to diagnose CTE and distinguish it from Alzheimer's or ALS. While CTE is a separate diagnosis, the symptoms are often similar to those found in Alzheimer's, Parkinson's and ALS, and can occur as the result of multiple concussions."