Concussion Symptoms Tied to Long-Term Cognitive Problems

Former National Football League players who had symptoms of concussion during their careers showed poorer performance on cognitive testing, compared with nonplayers, new research shows.

“Our results suggest that cognitive impacts of football-related concussion can be really long-lasting and these impacts may be coming from both concussive and subconcussive injury — that is, even head injuries that aren’t severe enough to lead to a concussion diagnosis,” study investigator Laura Germine, PhD, director of the Laboratory for Brain and Cognitive Health Technology, McLean Hospital, Boston, Massachusetts, told Medscape Medical News.

“When thinking about the risk of long-term cognitive impacts of concussion, it’s important [for clinicians] to evaluate concussion symptom history and not just the number of formally diagnosed concussions,” she said.

The study was published online March 2 in the Archives of Clinical Neuropsychology.

Underdiagnosed in Athletes

“While the impact of concussion in the short-term is well established and well understood, it is not as clear how concussion history affects cognitive functioning in the longer term among former professional football players,” Germine said.

Research examining the relationship between sports-related head injuries and long-term cognitive performance has yielded “mixed” results, possibly because of “differences between how cognitive performance is assessed, variations in sample characteristics, and inconsistencies in how concussion history is documented,” the researchers note.

They add that reporting an accurate number of concussions may be “challenging” because these injuries tend to be underdiagnosed in athletes. “Thus, measures that query previous concussion symptoms, rather than a specific number of concussions, have the potential to be more sensitive to cognitive performance.”

To investigate, the researchers collected data from 3975 former NFL players who filled out a 76-item health questionnaire between 2015 and 2019 that included 10 questions about their recollection of signs and symptoms of concussion following a blow to the head while playing football.

Participants provided information about demographics, current health conditions, diagnosed concussions, years of professional play, and age at first football exposure. They were later asked to complete a remote, unsupervised battery of 8 computerized cognitive tests through a platform called TestMyBrain (TMB), which is supported by McLean Hospital and Harvard Medical School.

The current study focused on a subset of 353 former NFL players (mean age, 54.3 years) who completed questionnaires on a computer or laptop, vs a cellphone or tablet, between 2018 and 2019.

Of this subset, 41.6% graduated college, 32.9% pursued education beyond college, 6.5% attended some college but did not graduate, and 19% were missing educational information.

Testing occurred an average of 29.3 years following the players’ final season of professional play.

The players’ cognitive performance was compared to that of 5086 male nonplayers (mean age, 45 years) who completed one or more of the cognitive tests.

Covariates included race/ethnicity, education, health-related factors, playing position, and duration of playing career.

Concussion Symptoms vs Diagnoses

After adjusting for age, the researchers found an association between recollected football concussion symptoms and overall cognitive performance (rp = −0.19 [95% CI, –0.09 to −0.29, B = −0.14, standard error of standardized beta coefficient [SE ] = .04, t = 3.61, P < .001).

In particular, recollected football concussion symptoms were associated with worse performance on the TMB Digit Symbol Matching, TMB Visual Paired Associates, and TMB Vocabulary tests.

Moreover, a concussion symptom score reflecting the number of times the former players experienced loss of consciousness following a blow to the head was significantly associated with worse cognitive performance (rp = −0.17 [–0.07 to −0.27] B = −0.15, SE = 0.05, t = 3.21, P = .001).

These findings remained unchanged, even after further adjustment for race, education, playing position, and all health-related variables.

In contrast, concussion diagnosis was not significantly associated with cognitive performance.

A follow-up analysis compared the cognitive performance of the former players to that of 5086 nonplayers. Overall, cognitive performance was found to be worse for the former players vs the nonplayers, after adjusting for age (all Ps < .001).

Larger differences in performance were found between younger and older former players than between younger and older nonplayers for two cognitive tests: the TMB trails B and TMB Digit Symbol Matching.

“Concussion diagnosis has changed over the years and is impacted by factors like underreporting of symptoms, changing criteria, and doesn’t take into account subconcussive head injury that still may impact cognitive health in the longer-term,” said Germane.

Additionally, “the impact of football exposure on cognitive health may be associated with accelerated cognitive aging effects, which are important to consider,” she suggested.

“While our findings aren’t conclusive in this respect, we did see the biggest differences in cognitive performance, compared with men of similar age, among older players,” she added.

The largest limitation of the study, the investigators note, was the lack of information regarding the former players’ premorbid or pre-injury cognitive functioning, since “premorbid estimates of cognitive ability are…critical for interpreting post-injury cognitive differences.”

Longitudinal Research Needed

Commenting for Medscape Medical News, Steven Flanagan, MD, professor of rehabilitation and chair of Rusk Rehabilitation at NYU Langone Health, New York City, noted that the “normative database was not matched to the player for multiple variables, such as but not limited to medical comorbidities that could potentially impact cognitive performance.”

Moreover, as mentioned by the authors, “the cognitive skills of the players prior to concussion exposure is unknown, which limits the conclusions from the study,” said Flanagan, who is also a member of the Concussion Center at NYU Langone.

And the study was cross-sectional, he pointed out. “A more accurate, although more intensive, challenging, time-consuming, and expensive means to evaluate long-term cognitive decline is a longitudinal study to look at change over time in the same subjects (including an appropriately matched control group).”

Nevertheless, the study “adds to the body of literature suggesting that repeated concussions (or in this case, the frequency of concussion-related symptoms, presumably due to the combination of diagnosed and nondiagnosed) over time results is cognitive decline,” continued Flanagan, who was not involved with the current study.

Germine is President and Director of the 501c3 nonprofit Many Brains Project, Inc., that supports open source cognitive tests for research. She previously served as Scientific Advisor to Sage Bionetworks, Inc. The other authors’ disclosures are listed on the original paper. Flanagan declares no relevant financial relationships.

Arch Clin Neuropsychol. Published online March 2, 2023. Abstract

Batya Swift Yasgur, MA, LSW is a freelance writer with a counseling practice in Teaneck, NJ. She is a regular contributor to numerous medical publications, including Medscape and WebMD, and is the author of several consumer-oriented health books as well as Behind the Burqa: Our Lives in Afghanistan and How We Escaped to Freedom (the memoir of two brave Afghan sisters who told her their story).

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