The study, published in the medical journal Neurology, found the NFL players were three times more likely to have neurodegenerative diseases than the general population.
The National Institute for Occupational Safety and Health, a division of the Centers for Disease Control, had been tracking a group of nearly 3,500 retired NFL players who were in the league from 1959 to 1988 for heart attack risk, CNN reported.
For the current study, the researchers examined the neurological outcomes of the players by specifically evaluating the autopsies of 334 players.
"We looked at all the death certificates, and Parkinson's, Alzheimer's and amyotrophic lateral sclerosis, or Lou Gehrig's disease, had significant contribution to the death," study co-author Elliot Lehman said in a statement.
The authors found among the 334 players, seven died from Alzheimer's and another seven from ALS. The average age of the players who died was age 57.
The numbers might seem small, but Lehman said: "These are generally rare diseases, especially at the younger age. Even when looking at the general population, you're generally going to have small numbers."