An Exploratory Study of Mild Cognitive Impairment of Retired Professional Contact Sport Athletes

Epidemiology, Pathophysiology, and Treatment Strategies of Concussions: A Comprehensive Review

A concussion is a particular manifestation of a traumatic brain injury, which is the leading cause of mortality and disabilities across the globe. The global prevalence of traumatic brain injury is estimated to be 939 instances per 100,000 individuals, with approximately 5.48 million people per year experiencing severe traumatic brain injury. Epidemiology varies amongst different countries by socioeconomic status with diverse clinical manifestations. Additionally, classifying concussions is an ambiguous process as clinical diagnoses are the only current classification method, and morbidity rates differ by demographic location as well as populations examined. In this article, we critically reviewed the pathophysiology of concussions, classification methods, treatment options available including both pharmacologic and nonpharmacologic intervention methods, etiologies as well as global etiologic differences associated with them, and clinical manifestations along with their associated morbidities. Furthermore, analysis of the current research regarding the incidence of concussion based traumatic brain injuries and future directions are discussed. Investigation on the efficacy of new therapeutic-related interventions such as exosome therapy and electromagnetic field stimulation are warranted to properly manage and treat concussion-induced traumatic brain injury.

Is contact sport participation associated with chronic traumatic encephalopathy or neurodegenerative decline? A systematic review and meta-analysis

INTRODUCTION

We sought to evaluate a potential association between contact vs. non-contact sport participation and long-term neurologic outcomes and chronic traumatic encephalopathy (CTE).

EVIDENCE ACQUISITION

PubMed/Embase/PsycINFO/CINAHL databases were queried for studies between 1950-2020 with contact and non-contact sports, longitudinal assessment >10 years, and long-term neurologic outcomes in four-domains: I) clinical diagnosis; II) CTE neuropathology; III) neurocognition; and IV) neuroimaging.

EVIDENCE SYNTHESIS

Of 2561 studies, 37 met inclusion criteria, and 19 contained homogenous outcomes usable in the meta-analysis. Domain I: Across six studies, no significant relationship was seen between contact sport participation and antemortem diagnosis of neurodegenerative disease or death related to such a diagnosis (RR1.88, P=0.054, 95%CI0.99, 3.49); however, marginal significance (P<0.10) was obtained. Domain II: Across three autopsy studies, no significant relationship was seen between contact sport participation and CTE neuropathology (RR42.39, P=0.086, 95%CI0.59, 3057.46); however, marginal significance (P<0.10) was obtained. Domain III: Across five cognitive studies, no significant relationship was seen between contact sport participation and cognitive function on the Trail Making Test (TMT) scores A/B (A:d=0.17, P=0.275,95% CI-0.13, 0.47; B:d=0.13, P=0.310, 95%CI-0.12, 0.38). Domain IV: In 10 brain imaging-based studies, 32% comparisons showed significant differences between those with a history of contact sport vs. those without.

CONCLUSIONS

No statistically significant increased risk of neurodegenerative diagnosis, CTE neuropathology, or neurocognitive changes was found to be associated with contact sport participation, yet marginal significance was obtained in two domains. A minority of imaging comparisons showed differences of uncertain clinical significance. These results highlight the need for longitudinal investigations using standardized contact sport participation and neurodegenerative criteria.

Diet's Impact on Post-Traumatic Brain Injury Depression: Exploring Neurodegeneration, Chronic Blood-Brain Barrier Destruction, and Glutamate Neurotoxicity Mechanisms

Traumatic brain injury (TBI) has a profound impact on cognitive and mental functioning, leading to lifelong impairment and significantly diminishing the quality of life for affected individuals. A healthy blood-brain barrier (BBB) plays a crucial role in guarding the brain against elevated levels of blood glutamate, making its permeability a vital aspect of glutamate regulation within the brain. Studies have shown the efficacy of reducing excess glutamate in the brain as a treatment for post-TBI depression, anxiety, and aggression. The purpose of this article is to evaluate the involvement of dietary glutamate in the development of depression after TBI. We performed a literature search to examine the effects of diets abundant in glutamate, which are common in Asian populations, when compared to diets low in glutamate, which are prevalent in Europe and America. We specifically explored these effects in the context of chronic BBB damage after TBI, which may initiate neurodegeneration and subsequently have an impact on depression through the mechanism of chronic glutamate neurotoxicity. A glutamate-rich diet leads to increased blood glutamate levels when contrasted with a glutamate-poor diet. Within the context of chronic BBB disruption, elevated blood glutamate levels translate to heightened brain glutamate concentrations, thereby intensifying neurodegeneration due to glutamate neurotoxicity.

Neurocognitive outcomes of older National Football League retirees

OBJECTIVE

Determine if head-injury exposure relates to later-in-life cognitive decline in older National Football League (NFL) retirees.

METHOD

NFL retirees (aged 50+) with or without cognitive impairment underwent baseline (n = 53) and follow-up (n = 29; 13-59 months later) neuropsychological evaluations. Cognitively normal (CN) retirees (n = 26) were age- and education-matched to healthy controls (n = 26). Cognitively impaired (CI) retirees with mild cognitive impairment or dementia (n = 27) were matched to a clinical sample (CS) by age, sex, education, and diagnosis (n = 83). ANOVAs compared neuropsychological composites at baseline and over time between retirees and their matched groups. Regression models evaluated whether concussions, concussions with loss of consciousness (LOC), or games played predicted neuropsychological functioning.

RESULTS

At baseline, CN retirees had slightly worse memory than controls (M_{CN retirees} = 50.69, SE_{CN retirees} = 1.320; M_{Healthy controls} = 57.08, SE_{Healthy controls} = 1.345; p = 0.005). No other group diferences were observed, and head-injury exposure did not predict neurocognitive performance at baseline or over time.

CONCLUSIONS

Head-injury exposure was not associated with later-in-life cognition, regardless of cognitive diagnosis. Some retirees may exhibit lower memory scores compared to age-matched peers, though this is of unclear clinical significance.

Mild Cognitive Impairment and Dementia Reported by Former Professional Football Players over 50 Years of Age: An NFL-LONG Study

PURPOSE

To estimate prevalences of MCI and dementia diagnoses in former National Football League (NFL) players ≥50 years old and examine the relationships among these diagnoses and an array of predictors of long-term brain health.

METHODS

A cross-section of former NFL players (n = 922; aged [mean ± SD] 64.8 ± 8.9 years) completed a questionnaire. Prevalences of self-reported medical diagnoses of MCI and dementia were reported alongside U.S. population estimates across 5-year age intervals (e.g., 60-64 years). Prevalence ratios (PRs) were calculated for multiple predictors of long-term brain health.

RESULTS

Overall, MCI and dementia prevalences were n = 219(23.8%) and n = 82(8.9%), respectively. Each diagnosis was more prevalent in former NFL players across age groups than U.S. norms, with greater disparities at relatively younger ages (e.g., 65-69) compared with older ages. Greater prevalences of MCI and dementia were associated with: self-reported concussion history (10+ vs. 0; PRadjusted[95%CI] = 1.66[1.02-2.71] and 2.61[1.01-6.71], respectively); recent pain intensity (PRadjusted[95%CI] = 1.13[1.07-1.20] and 1.15[1.03-1.28]); and diagnoses of depression (PRadjusted[95%CI] = 2.70[1.92-3.81] and 3.22[1.69-6.14]), anxiety (PRadjusted[95%CI] = 1.96[1.26-3.07] and 3.14[1.47-6.74]), or both (PRadjusted[95%CI] = 3.11[2.38-4.08] and 4.43[2.71-7.25]). Higher MCI prevalence was related to sleep apnea (PRadjusted[95%CI] = 1.30[1.06-1.60]); higher dementia prevalence was associated with age (5-year interval, PRadjusted[95%CI] = 1.42[1.26-1.60]) and race (non-White vs. White, PRadjusted[95%CI] = 1.64[1.07-2.53]).

CONCLUSIONS

Self-reported MCI and dementia prevalences were higher in former NFL players than national estimates and were associated with numerous personal factors, including mood-related disorders and a high number of self-reported concussions. Predictors of higher MCI and dementia prevalence may be modifiable and warrant consideration by clinicians and researchers as potential targets to mitigate the onset of these conditions.

Mortality from mental disorders and suicide in male professional American football and soccer players: A meta-analysis

OBJECTIVE

To determine the risk of mortality from mental disorders and suicide in professional sports associated with repeated head impacts.

METHODS

A systematic search was performed in PubMed, Web of Science, Scopus, and SPORTDiscus (since inception to June 8, 2021) to find studies comparing the incidence of mortality from mental disorders or suicide in former or active professional athletes of sports characterized by repeated head impacts vs athletes with no such exposure or the general non-athletic population.

RESULTS

Seven retrospective studies of moderate-to-high quality that included data from boxers and from basketball, ice hockey, soccer, and National Football League (NFL) players, respectively (total = 27 477 athletes, 100% male) met all inclusion criteria. Former male NFL players (n = 13 217) had a lower risk of mortality from mental disorders (standard mortality rate [SMR] = 0.30; 0.12-0.77; p = 0.012) and suicide (SMR = 0.54; 0.37-0.78; p < 0.001) than the general population. This finding was also corroborated in male soccer players (n = 13,065; SMR = 0.55; 0.46-0.67; p < 0.001). Male athletes participating in sports associated with repeated head impacts (n = 18,606) had also a lower risk of all-cause, cardiovascular disease (CVD), and cancer mortality (all p < 0.01) than the general population.

CONCLUSIONS

Participation of male athletes in American football or soccer at the professional level might confer a certain protective effect against mortality from mental disorders or suicide, besides its association with a lower risk of all-cause, CVD, or cancer-related mortality.

The Association of Physical (in)Activity with Mental Health. Differences between Elder and Younger Populations: A Systematic Literature Review

Background: Physical activity is associated with mental health benefits. This systematic literature review summarises extant evidence regarding this association, and explores differences observed between populations over sixty-five years and those younger than sixty-five. Methods: We reviewed articles and grey literature reporting at least one measure of physical activity and at least one mental disorder, in people of all ages. Results: From the 2263 abstracts screened, we extracted twenty-seven articles and synthesized the evidence regarding the association between physical (in)activity and one or more mental health outcome measures. We confirmed that physical activity is beneficial for mental health. However, the evidence was mostly based on self-reported physical activity and mental health measures. Only one study compared younger and elder populations, finding that increasing the level of physical activity improved mental health for middle aged and elder women (no association was observed for younger women). Studies including only the elderly found a restricted mental health improvement due to physical activity. Conclusions: We found inverse associations between levels of physical activity and mental health problems. However, more evidence regarding the effect of ageing when measuring associations between physical activity and mental health is needed. By doing so, prescription of physical activity could be more accurately targeted.

Health-promoting behaviours and concussion history are associated with cognitive function, mood-related symptoms and emotional-behavioural dyscontrol in former NFL players: an NFL-LONG Study

OBJECTIVES

To examine the relationships among self-reported sport-related concussion (SRC) history and current health-promoting behaviours (exercise frequency, diet quality and sleep duration) with self-reported measures of brain health (cognitive function, symptoms of depression and anxiety and emotional-behavioural dyscontrol) in former NFL players.

METHODS

In this cross-sectional study, a questionnaire was sent to former NFL players. Respondents reported SRC history (categorical: 0; 1-2; 3-5; 6-9; 10+ concussions), number of moderate-to-vigorous aerobic and resistance exercise sessions per week, diet quality (Rapid Eating Assessment for Participants-Shortened) and average nightly sleep duration. Outcomes were Patient-Reported Outcomes Measurement Information System Cognitive Function, Depression, and Anxiety, and Neuro-QoL Emotional-Behavioral Dyscontrol domain T-scores. Multivariable linear regression models were fit for each outcome with SRC history, exercise frequency, diet quality and sleep duration as explanatory variables alongside select covariates.

RESULTS

Multivariable regression models (n=1784) explained approximately 33%-38% of the variance in each outcome. For all outcomes, SRC history (0.144≤|β|≤0.217) was associated with poorer functioning, while exercise frequency (0.064≤|β|≤0.088) and diet quality (0.057≤|β|≤0.086) were associated with better functioning. Sleeping under 6 hours per night (0.061≤|β|≤0.093) was associated with worse depressive symptoms, anxiety and emotional-behavioural dyscontrol.

CONCLUSION

Several variables appear to be associated with mood and perceived cognitive function in former NFL players. SRC history is non-modifiable in former athletes; however, the effects of increasing postplaying career exercise frequency, making dietary improvements, and obtaining adequate sleep represent important potential opportunities for preventative and therapeutic interventions.

Long-Term Neurocognitive, Mental Health Consequences of Contact Sports

This article presents a brief history and literature review of chronic traumatic encephalopathy (CTE) in professional athletes that played contact sports. The hypothesis that CTE results from concussion or sub-concussive blows is based largely on several case series investigations with considerable bias. Evidence of CTE in its clinical presentation has not been generally noted in studies of living retired athletes. However, these studies also demonstrated limitation in research methodology. This paper aims to present a balanced perspective amidst a politically charged subject matter.

Mild Cognitive Impairment in Retired Professional Football Players With a History of Mild Traumatic Brain Injury: A Pilot Investigation

BACKGROUND

Traumatic brain injury (TBI) is a known risk factor for neurodegenerative dementias such as Alzheimer disease (AD); however, the potential risk of mild cases of TBI, such as concussions, remains unclear.

OBJECTIVE

To explore whether a small sample of retired professional athletes with a diagnosis of mild cognitive impairment (MCI)-the prodromal stage of AD-and a history of multiple mild TBIs exhibit greater neuropsychological impairment than age-matched nonathletes with MCI and no history of TBI.

METHOD

Ten retired National Football League players diagnosed with MCI and reporting multiple mild TBIs, and 10 nonathletes, also diagnosed with MCI but with no history of TBI, completed a standard neurologic examination and neuropsychological testing. Independent samples t tests were conducted to examine differences in neuropsychological performance between the two groups.

RESULTS

The retired athletes with a history of mild TBI obtained generally similar scores to the nonathlete controls on measures of verbal learning and memory, verbal fluency, and processing speed. However, the retired athletes scored lower than the controls on tests of confrontation naming and speeded visual attention.

CONCLUSION

Retired athletes with MCI and a history of mild TBI demonstrated similar neuropsychological profiles as nonathlete controls despite lower scores on measures of confrontation naming and speeded visual attention. These findings suggest that a history of multiple mild TBIs does not significantly alter the overall neuropsychological profile of individuals with MCI; confirmation of this will require longitudinal research with larger sample sizes.

Characterizing the Risk of Depression Following Mild Traumatic Brain Injury: A Meta-Analysis of the Literature Comparing Chronic mTBI to Non-mTBI Populations

Objective: Mild traumatic brain injury (mTBI) is associated with depressed mood acutely post-injury, but there is little evidence regarding long-term depression. The aim of this study was to determine the odds ratio (OR) of depression chronically following mTBI.

Methods: We searched Medline (PubMed), ProQuest, and Web of Science from date of database creation to January 23, 2019, for eligible studies examining depression at least 6 months post-injury in adult subjects with mTBI of any etiology, including civilians and military. Three authors independently reviewed titles and abstracts for study eligibility. Data were extracted and collated by two investigators. Risk of bias was assessed with the SIGN methodology. Study data were pooled using random-effects meta-analysis. The primary exposure was mTBI, and the primary outcome was depression. Secondary exploratory variables were time of assessment, age at injury, age at assessment, sex, and etiology.

Results: We included 47 cross-sectional studies (n = 25,103 mTBI and 29,982 control), 26 cohort studies (n = 70,119 mTBI, 262,034 control), four prospective observational studies (n = 1,058 mTBI and 733 control), two prospective longitudinal studies (n = 119 mTBI, 81 control), two case-control studies (n = 56 mTBI, 56 control), and one randomized controlled trial (n = 252 mTBI, 3,214 control). mTBI was associated with a 3.29-fold increased risk of depression (OR 3.29, 95% CI 2.68–4.03, I² = 96%). The OR for depression did not change when subjects were assessed at 6–12 months (OR 2.43, 1.45–4.07), years 1–2 (OR 4.12, 2.10–8.07); 2–10 (OR 3.28, 2.42–4.46), or 10+ (OR 3.42, 1.51–7.77). Similar risk of depression was sustained across different age at injury (<25: OR 2.26, 1.82–2.81; 25–35: OR 4.67, 3.06–7.14; >35: OR 2.69, 1.42–5.10) and different age at assessment (<40 years: OR 3.14, 2.48–3.99; >40 years: OR 4.57, 2.54–8.24). Female sex had a non-significant increase in OR (OR 19.97, 2.39–166.93) compared to male (OR 3.0, 2.33–3.86). mTBI etiology had no impact on depression.

Conclusions: Those experiencing mTBI are more than three times more likely to experience depression compared to those without a history of mTBI, and this risk remains decades beyond the mTBI event. Future longitudinal studies are needed to identify and mitigate this risk.

Concussion and long-term cognitive impairment among professional or elite sport-persons: a systematic review

INTRODUCTION

Understanding whether concussion in sport is associated with worsening cognitive function in later life will likely have immediate repercussion on sports concussion prevention and management policy and sporting rules and regulations. This systematic review aims to summarise the evidence on the association between concussion sustained by professional/elite athletes and long-term cognitive impairment.

METHODS

Embase, PubMed and Web of Science were used to search for eligible studies. Studies including professional/elite athletes from any sport were considered. Three comparison groups were considered: internal comparison (concussed vs non-concussed athletes within the same sample); between-sport comparison (contact sport athletes vs non-contact sports ones); external comparison (athletes vs samples of the general population or population norms).

RESULTS

14 studies were included (rugby, American football, ice hockey players, boxers and marital art fighters). The general quality of the evidence was poor. The overall evidence, weighted for type of comparison and study quality, points towards an association between sustaining a sport-related concussion and poorer cognitive function later in life in rugby, American football and boxing, although it is unclear to what extent this is clinically relevant. Data on ice hockey and martial arts were too sparse to allow conclusions to be drawn.

CONCLUSION

High-quality, appropriately designed and powered epidemiological studies are urgently needed to assess the association between sustaining a sport-related concussion and cognitive impairment later in life. Particular emphasis should be put on the clinical translational value of findings.

Neuropsychological functioning in ageing retired NFL players: a critical review

Recent discovery of chronic traumatic encephalopathy in former National Football League (NFL) players has led to a surge of papers investigating cognitive functioning in these former athletes. This critical review of the literature focused on the neuropsychological functioning in these ageing athletes, and included 22 articles published between 2013 and 2019, of which 13 reported on neuroradiological imaging and four focused on dose-response relationships of repetitive head injury on cognitive outcomes. Four studies suggest higher prevalence of MCI and neurodegenerative disease among NFL retirees, although a quantifiable risk and prevalence of cognitive impairment and dementia in these players remains unknown. Decreased verbal memory has been found in some players across multiple studies, though with unknown clinical significance due to small sample sizes, unreported effect sizes, and absence of longitudinal data. Studies investigating a dose-response relationship between cognitive decline and head injury have generated mixed findings utilizing various measures of head injury exposure. Neuroradiological findings are inconsistent, but suggest that some NFL players may be at greater risk for reduced white matter integrity. Future research is needed to understand the relationship between sports-related concussions and the risk of long-term cognitive decline and neurodegenerative disease in ageing NFL players.

Interactive Effects of Racial Identity and Repetitive Head Impacts on Cognitive Function, Structural MRI-Derived Volumetric Measures, and Cerebrospinal Fluid Tau and Aβ

BACKGROUND

Factors of increased prevalence among individuals with Black racial identity (e.g., cardiovascular disease, CVD) may influence the association between exposure to repetitive head impacts (RHI) from American football and later-life neurological outcomes. Here, we tested the interaction between racial identity and RHI on neurobehavioral outcomes, brain volumetric measures, and cerebrospinal fluid (CSF) total tau (t-tau), phosphorylated tau (p-tau181), and Aβ1 - 42 in symptomatic former National Football League (NFL) players.

METHODS

68 symptomatic male former NFL players (ages 40-69; n = 27 Black, n = 41 White) underwent neuropsychological testing, structural MRI, and lumbar puncture. FreeSurfer derived estimated intracranial volume (eICV), gray matter volume (GMV), white matter volume (WMV), subcortical GMV, hippocampal volume, and white matter (WM) hypointensities. Multivariate generalized linear models examined the main effects of racial identity and its interaction with a cumulative head impact index (CHII) on all outcomes. Age, years of education, Wide Range Achievement Test, Fourth Edition (WRAT-4) scores, CVD risk factors, and APOEε4 were included as covariates; eICV was included for MRI models. P-values were false discovery rate adjusted.

RESULTS

Compared to White former NFL players, Black participants were 4 years younger (p = 0.04), had lower WRAT-4 scores (mean difference = 8.03, p = 0.002), and a higher BMI (mean difference = 3.09, p = 0.01) and systolic blood pressure (mean difference = 8.15, p = 0.03). With regards to group differences on the basis of racial identity, compared to White former NFL players, Black participants had lower GMV (mean adjusted difference = 45649.00, p = 0.001), lower right hippocampal volume (mean adjusted difference = 271.96, p = 0.02), and higher p-tau181/t-tau ratio (mean adjusted difference = -0.25, p = 0.01). There was not a statistically significant association between the CHII with GMV, right hippocampal volume, or p-tau181/t-tau ratio. However, there was a statistically significant Race x CHII interaction for GMV (b = 2206.29, p = 0.001), right hippocampal volume (b = 12.07, p = 0.04), and p-tau181/t-tau ratio concentrations (b = -0.01, p = 0.004).

CONCLUSION

Continued research on racial neurological disparities could provide insight into risk factors for long-term neurological disorders associated with American football play.