Former professional football players who reported experiencing concussion symptoms during their playing careers were found to perform worse on a battery of cognitive tests than nonplayers, according to a study led by Mass General Brigham investigators from McLean Hospital and Spaulding Rehabilitation Network. Results of the study are published in Archives of Clinical Neuropsychology.
Of the more than 350 former National Football League (NFL) players who were studied an average of 29 years after their playing careers ended, those who reported experiencing concussion symptoms during their careers scored worse on assessments of episodic memory, sustained attention, processing speed, and vocabulary.
However, the number of concussions diagnosed by a medical professional or the length of a playing career had no observed effect on cognition.
A follow-up analysis compared the former players to more than 5,000 male volunteers in the general population who did not play professional football.
That analysis found that cognitive performance was generally worse for former players than nonplayers. While younger former players outperformed nonplayers on some tests, older retired players were more likely to perform worse than controls on cognitive tasks.
The researchers who led the study said that their results underline the importance of tracking concussion symptoms as opposed to diagnosed concussions in research.
This work also adds evidence to the impact a professional football career can have on accelerating cognitive aging.
“It is well-established that in the hours and days after a concussion, people experience some cognitive impairment. However, when you look decades out, the data on the long-term impact have been mixed,” said study senior author Laura Germine, PhD, director of the Laboratory for Brain and Cognitive Health Technology at McLean Hospital and an associate professor of psychiatry at Harvard Medical School (HMS).
“These new findings from the largest study of its kind show that professional football players can still experience cognitive difficulties associated with head injuries decades after they have retired from the sport.”
Concussion Symptoms Linked to Cognitive Performance
For the study, 353 retired NFL players completed hour-long neuropsychological tests through an online platform called TestMyBrain, which is supported by McLean and HMS. Players were fully remote and completed tests on a laptop or desktop that included assessments that measured processing speed, visual-spatial and working memory, and aspects of short- and long-term memory and vocabulary.
Recollected concussion symptoms were measured by asking the players the number of times they experienced any one of the following symptoms following a blow to the head during play or practice: headaches, nausea, dizziness, loss of consciousness, memory problems, disorientation, confusion, seizure, visual problems, or feeling unsteady on their feet.
They were also asked whether they lost consciousness during their careers, and whether they were ever diagnosed with a concussion by a medical professional.
The results showed that the former players’ cognitive performance (for example, on memory tasks) was negatively associated with recalled football concussion symptoms.
For example, differences observed in visual memory scores between former players with the highest and lowest reported concussion symptoms were equivalent to the differences in cognitive performance between a typical 35-year-old and 60-year-old.
However, poor cognitive performance was not associated with diagnosed concussions, years of professional play, or age of first football exposure.
The researchers noted that many head injuries or sub-concussive blows may not have been diagnosed as concussions due to a lack of awareness at the time or underreporting of symptoms by players.
When comparing the retired players to a group of 5,086 men who did not play football, cognitive performance was generally worse for former players.
On two tests of processing speed, age-related differences in cognitive performance were larger among the former player group than the nonplayer group, with older players performing worse.
These comparison data suggest that football exposure might accelerate age-related cognitive declines and produce greater disadvantages at older ages, according to the researchers, who added that more studies are needed to track cognitive performance in former players as they age.