Age of First Exposure to Football Is Not Associated with Midlife Brain Health Problems

American Football Play and Parkinson Disease Among Men

Importance

Parkinsonism and Parkinson disease (PD) are known to result from repetitive head impacts from boxing. Repetitive head impacts from American football may also be associated with increased risk of neurodegenerative pathologies that cause parkinsonism, yet in vivo research on the association between football play and PD is scarce and limited by small samples and equivocal findings.

Objective

To evaluate the association between football participation and self-reported parkinsonism or PD diagnosis.

Design, Setting, and Participants

This cross-sectional study leveraged data from the online Fox Insight study. Participants completed online questionnaires and self-reported whether they currently had a diagnosis of Parkinson disease or parkinsonism by a physician or other health care professional. In November 2020, the Boston University Head Impact Exposure Assessment was launched for data collection on repetitive head impacts. Data used for this manuscript were obtained from the Fox Insight database on June 9, 2022. A total of 1875 men who endorsed playing any organized sport were included. Former athletes were divided into those who participated in football (n = 729 [38.9%]) and those who participated in other sports (reference group).

Exposures

Self-reported participation in football, duration and level of football play, age at first exposure.

Main Outcomes and Measures

Logistic regression tested associations between PD status and history of football play, duration of football play, highest level played, and age at first exposure, controlling for age, education, history of diabetes or heart disease, body mass index, history of traumatic brain injury with loss of consciousness, and family history of PD.

Results

In this sample of 1875 men (mean [SD] age, 67.69 [9.84] years) enriched for parkinsonism or PD (n = 1602 [85.4%]), 729 (38.9%) played football (mean [SD] duration, 4.35 [2.91] years). History of playing football was associated with higher odds of having a parkinsonism or PD diagnosis (odds ratio [OR], 1.61; 95% CI, 1.19-2.17). Among the entire sample, longer duration of play was associated with higher odds of having a parkinsonism or PD diagnosis (OR, 1.12; 95% CI, 1.06-1.19). Among football players, longer duration of football play (OR, 1.12; 95% CI, 1.02-1.23) and higher level of play (OR, 2.93; 95% CI, 1.28-6.73) were associated with higher odds of having parkinsonism or PD.

Conclusions and Relevance

In this cross-sectional study of participants enriched for PD, participation in football was associated with higher odds of having a reported parkinsonism or PD diagnosis.

Examining later-in-life health risks associated with sport-related concussion and repetitive head impacts: a systematic review of case-control and cohort studies

OBJECTIVE

Concern exists about possible problems with later-in-life brain health, such as cognitive impairment, mental health problems and neurological diseases, in former athletes. We examined the future risk for adverse health effects associated with sport-related concussion, or exposure to repetitive head impacts, in former athletes.

DESIGN

Systematic review.

DATA SOURCES

Search of MEDLINE, Embase, Cochrane, CINAHL Plus and SPORTDiscus in October 2019 and updated in March 2022.

ELIGIBILITY CRITERIA

Studies measuring future risk (cohort studies) or approximating that risk (case-control studies).

RESULTS

Ten studies of former amateur athletes and 18 studies of former professional athletes were included. No postmortem neuropathology studies or neuroimaging studies met criteria for inclusion. Depression was examined in five studies in former amateur athletes, none identifying an increased risk. Nine studies examined suicidality or suicide as a manner of death, and none found an association with increased risk. Some studies comparing professional athletes with the general population reported associations between sports participation and dementia or amyotrophic lateral sclerosis (ALS) as a cause of death. Most did not control for potential confounding factors (eg, genetic, demographic, health-related or environmental), were ecological in design and had high risk of bias.

CONCLUSION

Evidence does not support an increased risk of mental health or neurological diseases in former amateur athletes with exposure to repetitive head impacts. Some studies in former professional athletes suggest an increased risk of neurological disorders such as ALS and dementia; these findings need to be confirmed in higher quality studies with better control of confounding factors.

PROSPERO REGISTRATION NUMBER

CRD42022159486.

Effects of contact/collision sport history on gait in early- to mid-adulthood

BACKGROUND

To determine the effect of contact/collision sport participation on measures of single-task (ST) and dual-task (DT) gait among early- to middle-aged adults.

METHODS

The study recruited 113 adults (34.88 ± 11.80 years, (mean ± SD); 53.0% female) representing 4 groups. Groups included (a) former non-contact/collision athletes and non-athletes who are not physically active (n = 28); (b) former non-contact/collision athletes who are physically active (n = 29); (c) former contact/collision sport athletes who participated in high-risk sports and are physically active (n = 29); and (d) former rugby players with prolonged repetitive head impact exposure history who are physically active (n = 27). Gait parameters were collected using inertial measurement units during ST and DT gait. DT cost was calculated for all gait parameters (double support, gait speed, and stride length). Groups were compared first using one-way analysis of covariance. Then a multiple regression was performed for participants in the high-risk sport athletes and repetitive head impact exposure athletes groups only to predict gait outcomes from contact/collision sport career duration.

RESULTS

There were no significant differences between groups on any ST, DT, or DT cost outcomes (p > 0.05). Contact/collision sport duration did not predict any ST, DT, or DT cost gait outcomes.

CONCLUSION

Years and history of contact/collision sport participation does not appear to negatively affect or predict neurobehavioral function in early- to mid-adulthood among physically active individuals.

White matter hyperintensities in former American football players

INTRODUCTION

The presentation, risk factors, and etiologies of white matter hyperintensities (WMH) in people exposed to repetitive head impacts are unknown. We examined the burden and distribution of WMH, and their association with years of play, age of first exposure, and clinical function in former American football players.

METHODS

A total of 149 former football players and 53 asymptomatic unexposed participants (all men, 45-74 years) completed fluid-attenuated inversion recovery magnetic resonance imaging, neuropsychological testing, and self-report neuropsychiatric measures. Lesion Segmentation Toolbox estimated WMH. Analyses were performed in the total sample and stratified by age 60.

RESULTS

In older but not younger participants, former football players had greater total, frontal, temporal, and parietal log-WMH compared to asymptomatic unexposed men. In older but not younger former football players, greater log-WMH was associated with younger age of first exposure to football and worse executive function.

DISCUSSION

In older former football players, WMH may have unique presentations, risk factors, and etiologies.

HIGHLIGHTS

Older but not younger former football players had greater total, frontal, temporal, and parietal lobe white matter hyperintensities (WMH) compared to same-age asymptomatic unexposed men. Younger age of first exposure to football was associated with greater WMH in older but not younger former American football players. In former football players, greater WMH was associated with worse executive function and verbal memory.

Association Between Head Impact Exposure, Psychological Needs, and Indicators of Mental Health Among U.S. High School Tackle Football Players

PURPOSE

Age of first exposure to tackle football and head impact kinematics have been used to examine the effect of head impacts on mental health outcomes. These measures coupled with retrospective and cross-sectional designs have contributed to conflicting results. The purpose of this study was to identify the effect of one season of head impact exposure, age of first exposure to football, and psychological need satisfaction on acute mental health outcomes in adolescent football players.

METHODS

This prospective single-season cohort study used sensor-installed mouthguards to collect head impact exposure along with surveys to assess age of first exposure to football, psychological satisfaction, depressive symptoms, anxiety symptoms, and thriving from football players at four high schools (n = 91). Linear regression was used to test the association of head impact exposure, age of first exposure, and psychological satisfaction with acute mental health outcomes.

RESULTS

A total of 9,428 impacts were recorded with a mean of 102 ± 113 impacts/player. Cumulative head impact exposure and age of first exposure were not associated with acute mental health outcomes at postseason or change scores from preseason to postseason. Greater psychological satisfaction was associated with fewer depressive symptoms (β = -0.035, SE = 0.008, p = < .001), fewer anxiety symptoms (β = -0.021, SE = 0.008, p = .010), and greater thriving scores (β = 0.278, SE = 0.040, p = < .001) at postseason.

DISCUSSION

This study does not support the premise that greater single-season head impact exposure or earlier age of first exposure to tackle football is associated with worse acute mental health indicators over the course of a single season in adolescent football players.

Long-Term Changes in Brain Connectivity Reflected in Quantitative Electrophysiology of Symptomatic Former National Football League Players

Exposure to repetitive head impacts (RHI) has been associated with long-term disturbances in cognition, mood, and neurobehavioral dysregulation, and reflected in neuroimaging. Distinct patterns of changes in quantitative features of the brain electrical activity (quantitative electroencephalogram [qEEG]) have been demonstrated to be sensitive to brain changes seen in neurodegenerative disorders and in traumatic brain injuries (TBI). While these qEEG biomarkers are highly sensitive at time of injury, the long-term effects of exposure to RHI on brain electrical activity are relatively unexplored. Ten minutes of eyes closed resting EEG data were collected from a frontal and frontotemporal electrode montage (BrainScope Food and Drug Administration-cleared EEG acquisition device), as well as assessments of neuropsychiatric function and age of first exposure (AFE) to American football. A machine learning methodology was used to derive a qEEG-based algorithm to discriminate former National Football League (NFL) players (n = 87, 55.40 ± 7.98 years old) from same-age men without history of RHI (n = 68, 54.94 ± 7.63 years old), and a second algorithm to discriminate former players with AFE <12 years (n = 33) from AFE ≥12 years (n = 54). The algorithm separating NFL retirees from controls had a specificity = 80%, a sensitivity = 60%, and an area under curve (AUC) = 0.75. Within the NFL population, the algorithm separating AFE <12 from AFE ≥12 resulted in a sensitivity = 76%, a specificity = 52%, and an AUC = 0.72. The presence of a profile of EEG abnormalities in the NFL retirees and in those with younger AFE includes features associated with neurodegeneration and the disruption of neuronal transmission between regions. These results support the long-term consequences of RHI and the potential of EEG as a biomarker of persistent changes in brain function.

Examining associations between concussion history, subjectively experienced memory problems, and general health factors in older men

OBJECTIVE

Examine associations between subjective memory complaints (SMCs), concussion history, and cognitive, psychological, and physical health in older men from the general population.

METHOD

Participants were 504 men aged 50-79 who were recruited using an online labor market. Participants completed a survey assessing demographics, medication history, concussion history, recent memory problems, and additional aspects of recent cognitive, mental, and physical health.

RESULTS

Men with a lifetime history of ≥3 concussions also reported a lifetime history of being prescribed medication for anxiety (46.8%), depression (43.5%), chronic pain (79.0%), and high blood pressure (66.1%). When asked about symptoms experienced over the past year and the past week, they endorsed higher rates of cognitive and mental health problems, migraines, and difficulties with sleep and fatigue. The multivariable logistic regression model for predicting mild or greater memory problems was significant, χ2(8) = 168.97, p < .001. In unadjusted analyses, significant predictors, in order of magnitude (strongest to weakest), were fatigue (odds ratio [OR] = 3.21), back or neck pain (OR = 2.28), migraines (OR = 2.11), anxiety (OR = 2.07), depression (OR = 2.04), difficulty sleeping (OR = 1.98), and concussion history (OR = 1.49). In the multivariable model, only back or neck pain (OR = 1.51, p = .004) and fatigue (OR = 1.99, p = .004) were significant predictors.

CONCLUSIONS

A personal history of multiple concussions was associated with perceived memory problems, but to a lesser degree than fatigue, back or neck pain, and migraines.

Relating American Football Age of First Exposure to Patient-Reported Outcomes and Medical Diagnoses Among Former National Football League Players: An NFL-LONG study

BACKGROUND

The age of first exposure (AFE) to American football participation is a growing concern for late-life function. Mixed evidence exists surrounding AFE and may be attributed to varied methods employed across studies.

OBJECTIVE

To examine the associations between AFE to American football participation with measures of cognitive, behavioral, and physical function and brain-related medical diagnoses across age categories among former National Football League players.

METHODS

We conducted a cross-sectional survey of 1784 former players (age: 52.3 ± 16.3 years, AFE: 11.3 ± 2.9 years, years of football: 17.5 ± 4.5 years, 86.9% ≥ one lifetime concussion). Players completed a general health questionnaire recording demographics, football playing history (including AFE), and diagnoses (anxiety, depression, any form of dementia, mild cognitive impairment). Players completed Patient-Reported Outcomes Measurement Information System (PROMIS) measures assessing domains of cognitive and physical function, anxiety, depression, sleep disturbance, pain interference, and emotional-behavioral dyscontrol. Multivariable linear and binomial regression models were used to examine the associations of AFE and age with PROMIS outcomes and diagnoses, respectively.

RESULTS

No significant AFE by age interactions were detected for PROMIS outcomes (p ≥ 0.066) or diagnoses (p ≥ 0.147). Younger AFE associated with higher PROMIS scores of anxiety (B = - 0.22, p = 0.016), depression (B = - 0.22, p = 0.010), sleep disturbances (B = - 0.16, p = 0.007), pain interference (B = - 0.19, p = 0.014), and emotional-behavioral dyscontrol (B = - 0.22, p = 0.019). Age was associated with all PROMIS outcomes (p ≤ 0.042). AFE was not associated with the prevalence of anxiety, depression, dementia, or mild cognitive impairment (p ≥ 0.449), while age was (p ≤ 0.013).

CONCLUSIONS

AFE was significantly associated with PROMIS outcomes, albeit low-strength associations (i.e., effect sizes), but not with diagnoses. Our findings indicate AFE is a significant but minor contributing factor for health-related quality of life in this cohort. Future work should incorporate additional characterizations of cumulative head impacts and related factors when examining long-term outcomes associated with football participation.

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.

Incremental Effects of Subsequent Concussions on Cognitive Symptoms in the Sport Concussion Assessment Tool

OBJECTIVE

Patients who are fully recovered from a concussion may still be more vulnerable in the face of subsequent concussions. This study examines symptoms associated with repeated concussions in young and otherwise healthy adults.

DESIGN

Cross sectional.

SETTING

Institutional study at a university setting.

PARTICIPANTS

University students with a history of concussion.

INDEPENDENT VARIABLES

Participants were grouped based on numbers of concussions.

MAIN OUTCOME MEASURES

The impact of incremental concussion on symptom clusters in Sport Concussion Assessment Tools 5 and Spearman ranking correlation coefficients between symptom clusters.

RESULTS

One hundred thirty-five participants reported having had 1 concussion, 63 reported 2 concussions, 50 reported 3 concussions, and 43 reported 4 to 6 concussions. Total severity scores over the range of concussion number (1, 2, 3, and greater than 3) did not show a clear incremental effect. However, average scores of cognitive symptoms rose with each subsequent concussion ( P ≤ 0.05). The largest incremental effect observed was that of second concussions on emotional symptom scores (t = 5.85, P < 0.01). Symptoms in the emotional and cognitive clusters were the most correlated regardless of the number of reported concussions; the correlations were lowest with symptoms associated with sensitivity to light or noise.

CONCLUSIONS

The incremental rise of cognitive symptom scores with each concussion affirms the importance of cognitive impairment in concussion assessment and implies a cumulative brain vulnerability that persists even after symptom resolution. The cognitive-emotional symptom clusters may reflect underlying concussion-induced impairments in the corticostriatothalamocortical (CSTC) networks, although sensitivity symptoms are potentially attributable to different neural correlates.

Quantifying and Examining Reserve in Symptomatic Former National Football League Players

BACKGROUND

Repetitive head impacts (RHI) from contact sports have been associated with cognitive and neuropsychiatric disorders. However, not all individuals exposed to RHI develop such disorders. This may be explained by the reserve hypothesis. It remains unclear if the reserve hypothesis accounts for the heterogenous symptom presentation in RHI-exposed individuals. Moreover, optimal measurement of reserve in this population is unclear and likely unique from non-athlete populations.

OBJECTIVE

We examined the association between metrics of reserve and cognitive and neuropsychiatric functioning in 89 symptomatic former National Football League players.

METHODS

Individual-level proxies (e.g., education) defined reserve. We additionally quantified reserve as remaining residual variance in 1) episodic memory and 2) executive functioning performance, after accounting for demographics and brain pathology. Associations between reserve metrics and cognitive and neuropsychiatric functioning were examined.

RESULTS

Higher reading ability was associated with better attention/information processing (β=0.25; 95% CI, 0.05-0.46), episodic memory (β=0.27; 95% CI, 0.06-0.48), semantic and phonemic fluency (β=0.24; 95% CI, 0.02-0.46; β=0.38; 95% CI, 0.17-0.59), and behavioral regulation (β=-0.26; 95% CI, -0.48, -0.03) performance. There were no effects for other individual-level proxies. Residual episodic memory variance was associated with better attention/information processing (β=0.45; 95% CI, 0.25, 0.65), executive functioning (β=0.36; 95% CI, 0.15, 0.57), and semantic fluency (β=0.38; 95% CI, 0.17, 0.59) performance. Residual executive functioning variance was associated with better attention/information processing (β=0.44; 95% CI, 0.24, 0.64) and episodic memory (β=0.37; 95% CI, 0.16, 0.58) performance.

CONCLUSION

Traditional reserve proxies (e.g., years of education, occupational attainment) have limitations and may be unsuitable for use in elite athlete samples. Alternative approaches of reserve quantification may prove more suitable for this population.

Age of First Exposure to Contact and Collision Sports and Later in Life Brain Health: A Narrative Review

A controversial theory proposes that playing tackle football before the age of 12 causes later in life brain health problems. This theory arose from a small study of 42 retired National Football League (NFL) players, which reported that those who started playing tackle football at a younger age performed worse on selected neuropsychological tests and a word reading test. The authors concluded that these differences were likely due to greater exposure to repetitive neurotrauma during a developmentally sensitive maturational period in their lives. Several subsequent studies of current high school and collegiate contact/collision sports athletes, and former high school, collegiate, and professional tackle football players have not replicated these findings. This narrative review aims to (i) discuss the fundamental concepts, issues, and controversies surrounding existing research on age of first exposure (AFE) to contact/collision sport, and (ii) provide a balanced interpretation, including risk of bias assessment findings, of this body of evidence. Among 21 studies, 11 studies examined former athletes, 8 studies examined current athletes, and 2 studies examined both former and current athletes. Although the literature on whether younger AFE to tackle football is associated with later in life cognitive, neurobehavioral, or mental health problems in former NFL players is mixed, the largest study of retired NFL players (N = 3,506) suggested there was not a significant association between earlier AFE to organized tackle football and worse subjectively experienced cognitive functioning, depression, or anxiety. Furthermore, no published studies of current athletes show a significant association between playing tackle football (or other contact/collision sports) before the age of 12 and cognitive, neurobehavioral, or mental health problems. It is important to note that all studies were judged to be at high overall risk of bias, indicating that more methodologically rigorous research is needed to understand whether there is an association between AFE to contact/collision sports and later in life brain health. The accumulated research to date suggests that earlier AFE to contact/collision sports is not associated with worse cognitive functioning or mental health in (i) current high school athletes, (ii) current collegiate athletes, or (iii) middle-aged men who played high school football. The literature on former NFL players is mixed and does not, at present, clearly support the theory that exposure to tackle football before age 12 is associated with later in life cognitive impairment or mental health problems.

Age of First Exposure to Football Is Not Associated With Later-in-Life Cognitive or Mental Health Problems

Background: The purpose of this study was to determine if earlier age of first exposure to football is associated with worse brain health in middle-aged and older adult men who played high school football.

Methods: Men from the United States, aged 35 and older, who reported playing high school football, completed a customized, online health survey via the Amazon Mechanical Turk (mTurk) platform. Survey items included physical, psychological, and cognitive symptoms over the past week and over the past year, sports participation history (including age of first exposure to football), medical history, and concussion history. Participants also completed the Patient Health Questionnaire-8 (PHQ-8) and the British Columbia Post-Concussion Symptom Inventory (BC-PSI).

Results: There were 186 men (age M = 51.78, SD = 10.93) who participated in high school football, and 87 (46.8%) reported football participation starting before the age of 12 and 99 (53.2%) reported football participation at or after the age of 12. Those who started playing football at an earlier age reported a greater number of lifetime concussions (M = 1.95, SD = 1.79) compared to those who started playing at age 12 or later (M = 1.28, SD = 1.52; U = 3,257.5, p = 0.003). A similar proportion of men who played football before vs. after the age of 12 reported a lifetime history of being prescribed medications for depression, anxiety, chronic pain, headaches, or memory problems. When comparing men who played football before vs. after the age of 12, the groups did not differ significantly in their ratings of depression, anger, anxiety, headaches, migraines, neck or back pain, chronic pain, concentration problems, or memory problems over the past week or the past year. The two groups did not differ significantly in their ratings of current symptoms of depression (PHQ-8; U = 4,187.0, p = 0.74) or post-concussion-like symptoms (BC-PSI; U = 3,944.0, p = 0.53). Furthermore, there were no statistically significant correlations between the age of first exposure to football, as a continuous variable, and PHQ-8 or BC-PSI scores.

Conclusion: This study adds to a rapidly growing body of literature suggesting that earlier age of first exposure to football is not associated with later-in-life brain health.