Chronic traumatic encephalopathy in contact sports: a systematic review of all reported pathological cases

Fist fighting and increased mortality post-retirement among National Hockey League players

OBJECTIVE

Fist fighting among hockey players is thought to have long-term impacts on health. Because of methodological concerns of previous studies, we undertook a retrospective cohort study among retired National Hockey League (NHL) players to estimate rates of all-cause mortality according to the cumulative number of fights in their careers.

METHODS

The cohort comprised male hockey players, excluding goaltenders, who played in the NHL from 1967 to 2022. We compiled their birth and death data, body mass index at entry, and other characteristics of playing. We used the proportional hazards model, with age at retirement as the time axis, to estimate mortality rates through July 31, 2024, in relation to the total number of fights in the NHL. Hazard ratios (HR) were adjusted for body mass index and year starting in the NHL. Mean survival after retirement by fighting status was also computed.

RESULTS

Among the 5411 retired players, 407 had died, 2082 (38.5%) never fought, and 759 (14.0%) fought ≥ 30 times. We found a positive linear response between the total number of fights and the risk of mortality: the adjusted HR per 10 fights was 1.04 (95% CI, 1.01, 1.07). Using this estimate, compared to non-fighters, the HR for five fights was 1.02 (95% CI, 1.00, 1.03), and for 50 fights it was 1.20 (95% CI, 1.02, 1.41). The mean loss of survival among those who fought ≥ 10 times compared with ≤ 1 time was 2.5, 2.1, and 1.5 years for those who started playing in 1970, 1980, and 1992, respectively.

CONCLUSION

Our findings suggest that fighting in NHL games increases rates of mortality post-retirement, but that these impacts are substantially less than reported previously. We recommend that the NHL establish standardized methods for collecting fight data to more accurately capture the lifetime fighting history and its associated health impacts for its players.

A comparison of head impact characteristics during elite men's Rugby Union fifteens and sevens match play

Different forms of rugby may pose distinct risks to head injury. Video of rugby match footage was analyzed using head impact magnitude, frequency, and time interval for 15s and 7s athletes. Impacts were reconstructed in laboratory, and finite element modeling was used to estimate maximum principal strain. No difference was found in impact frequency or time interval between the two forms. Significantly more head impacts of higher severity levels were documented during 7s. These findings provide objective comparisons between 7s and 15s which may guide risk mitigation strategies in managing brain trauma for specific forms of rugby.

Most cited articles involving lacrosse since 1990 primarily focus on concussion and traumatic brain injury

OBJECTIVES

The purpose of this study was to identify the 50 most-cited publications relating to lacrosse since 1990 and conduct a bibliometric analysis of the identified studies.

METHODS

Clarivate Analytics Web of Science database was queried to identify all publication titles, abstracts, and keywords for the term 'lacrosse' on 9 June 2023. The resulting articles were sorted by total number of citations. Titles and abstracts were included based on their relevance to lacrosse. Once the 50 most cited articles were identified, each article was further analyzed to obtain author name, publication year, country of origin, journal name, article type, research topic, competition level, total number of citations, and the level of evidence. Citation density (total number of citations/years since publication) was calculated and recorded for each of the most-cited studies.

RESULTS

The 50 most-cited articles were cited 4237 of times with an average of 84 citations per article. The most cited article was cited 637 (15.0%) times. The articles came from 2 different countries, with the United States and Australia comprising 49 and 1 articles, respectively. All articles were published in English. The American Journal of Sports Medicine published the most articles (n = 21, 42.0%). The most studied topic was concussion/traumatic brain injury (n = 18) followed by studies assessing all injuries (n = 7). Collegiate-level lacrosse was the most studied level of competition (n = 22), while high school-level followed (n = 12).

CONCLUSIONS

The majority of the 50 most-cited articles related to lacrosse since 1990 focus on the prevalence, diagnosis and identification of concussion/traumatic brain injury in high school and collegiate-level athletes. These articles are predominantly epidemiological or cohort studies with Level III or IV evidence that almost unanimously originate from the United States.

Nandrolone Abuse Prior to Head Trauma Mitigates Endoplasmic Reticulum Stress, Mitochondrial Bioenergetic Deficits, and Markers of Neurodegeneration

The abuse of synthetic steroids, such as nandrolone decanoate (ND), is often associated with violent behavior, increasing the risk of traumatic brain injury (TBI). After a TBI, proteins like APP, β-amyloid peptide-42 (Aβ42), and phosphorylated tau (pTau) accumulate and trigger endoplasmic reticulum (ER) stress associated with an unfolded protein response (UPR). The involvement of mitochondrial bioenergetics in this context remains unexplored. We interrogate whether the abuse of ND before TBI alters the responses of ER stress and mitochondrial bioenergetics in connection with neurodegeneration and memory processing in mice. Male CF1 adult mice were administered ND (15 mg/kg) or vehicle (VEH) s.c. for 19 days, coinciding with the peak day of aggressive behavior, and then underwent cortical controlled impact (CCI) or sham surgery. Spatial memory was assessed through the Morris water maze task (MWM) post-TBI. In synaptosome preparations, i) we challenged mitochondrial complexes (I, II, and V) in a respirometry assay, employing metabolic substrates, an uncoupler, and inhibitors; and ii) assessed molecular biomarkers through Western blot. TBI significantly increased APP, Aβ42, and pTauSer396 levels, along with ER-stress proteins, GRP78, ATF6, and CHOP, implying it primed apoptotic signaling. Concurrently, TBI reduced mitochondrial Ca2+ efflux in exchange with Na+, disturbed the formation/dissipation of membrane potential, increased H2O2 production, decreased biogenesis (PGC-1⍺ and TOM20), and ATP biosynthesis coupled with oxygen consumption. Unexpectedly, ND abuse before TBI attenuated the elevations in APP, Aβ42, and pTauSer396, accompanied by a decrease in GRP78, ATF6, and CHOP levels, and partial normalization of mitochondrial-related endpoints. A principal component analysis revealed a key hierarchical signature featuring mitochondrial Ca2+ efflux, CHOP, GRP78, TOM20, H2O2, and bioenergetic efficiency as a unique variable (PC1) able to explain the memory deficits caused by TBI, as well as the preservation of memory fitness induced by prior ND abuse.

Injuries in Male and Female Wrestlers

» With historical exclusion from the sport and lack of research on the subject, there is a paucity of data regarding the injury incidence, treatment, and recovery of female wrestlers as compared with their male counterparts.» Data demonstrate that female wrestlers are more likely to experience sprains/strains, whereas male wrestlers experience more concussions and fractures.» Variations in behavior and physiology including risk-taking habits and ligament laxity may contribute to differences in injury incidence between male and female wrestlers.» Rapid weight loss and eating disorders are important areas of future investigation for male and female wrestlers alike.

Chronic traumatic encephalopathy pathognomonic lesions occurring in isolation adjacent to infiltrative and non-infiltrative white matter lesions

Chronic traumatic encephalopathy (CTE) is defined by perivascular neuronal phosphorylated-tau accumulation at cortical sulcal depths. CTE has been mainly described in the context of repetitive, impact-type traumatic brain injury (rTBI), principally from contact sports. Rarely, CTE has been associated with single TBIs, including in relationship to healed leucotomy sites in brains from formerly institutionalized psychiatric patients without documented rTBI. Given that leucotomy principally involves severing of white matter, this could suggest involvement of axonal injury in CTE pathophysiology. We present three cases wherein isolated CTE pathology was identified adjacent to distinct white matter lesions. Case 1 is a 41-year-old man with history of hereditary hemorrhagic telangiectasia and resection of a cerebral arteriovenous malformation (AVM). Case 2 is a 46-year-old man with glioblastoma. Case 3 is a 52-year-old man with a remote cerebral infarct. Isolated CTE lesions were found adjacent to the aforementioned pathologies in each case. Additional CTE lesions were not identified despite extensive sampling. Multiple age-related tau astrogliopathy (ARTAG)-like lesions were also identified at other sulcal depths near the AVM resection site in Case 1. These cases may provide insights regarding the pathophysiology of the CTE pathognomonic lesion and the development of ARTAG-like pathology adjacent to long-standing mass lesions.

Unusual combinations of neurodegenerative pathologies with chronic traumatic encephalopathy (CTE) complicates clinical prediction of CTE

BACKGROUND AND PURPOSE

Chronic traumatic encephalopathy (CTE) has gained widespread attention due to its association with multiple concussions and contact sports. However, CTE remains a postmortem diagnosis, and the link between clinical symptoms and CTE pathology is poorly understood. This study aimed to investigate the presence of copathologies and their impact on symptoms in former contact sports athletes.

METHODS

This was a retrospective case series design of 12 consecutive cases of former contact sports athletes referred for autopsy. Analyses are descriptive and include clinical history as well as the pathological findings of the autopsied brains.

RESULTS

All participants had a history of multiple concussions, and all but one had documented progressive cognitive, psychiatric, and/or motor symptoms. The results showed that 11 of the 12 participants had evidence of CTE in the brain, but also other copathologies, including different combinations of tauopathies, and other rare entities.

CONCLUSIONS

The heterogeneity of symptoms after repetitive head injuries and the diverse pathological combinations accompanying CTE complicate the prediction of CTE in clinical practice. It is prudent to consider the possibility of multiple copathologies when clinically assessing patients with repetitive head injuries, especially as they age, and attributing neurological or cognitive symptoms solely to presumptive CTE in elderly patients should be discouraged.

Tau Imaging in Late Traumatic Brain Injury: A [18F]MK-6240 Positron Emission Tomography Study

Epidemiological studies have identified prior traumatic brain injury (TBI) as a risk factor for developing Alzheimer's disease (AD). Neurofibrillary tangles (NFTs) are common to AD and chronic traumatic encephalopathy following repetitive mild TBI. However, it is unclear if a single TBI is sufficient to cause accumulation of NFTs. We performed a [18F]MK-6240 positron emission tomography (PET) imaging study to assess NFTs in patients who had sustained a single TBI at least 2 years prior to study inclusion. Fourteen TBI patients (49 ± 20 years; 5 M/9 F; 8 moderate-severe, 1 mild-probable, 5 symptomatic-possible TBI) and 40 demographically similar controls (57 ± 19 years; 19 M/21 F) underwent simultaneous [18F]MK-6240 PET and magnetic resonance imaging (MRI) as well as neuropsychological assessment including the Cambridge Neuropsychological Test Automated Battery (CANTAB). A region-based voxelwise partial volume correction was applied, using parcels obtained by FreeSurfer v6.0, and standardized uptake value ratios (SUVR) were calculated relative to the cerebellar gray matter. Group differences were assessed on both a voxel- and a volume-of-interest-based level and correlations of [18F]MK-6240 SUVR with time since injury as well as with clinical outcomes were calculated. Visual assessment of TBI images did not show global or focal increases in tracer uptake in any subject. On a group level, [18F]MK-6240 SUVR was not significantly different in patients versus controls or between subgroups of moderate-severe TBI versus less severe TBI. Within the TBI group, One Touch Stockings problem solving and spatial working memory (executive function), reaction time (attention), and Mini-Mental State Examination (MMSE) (global cognition) were associated with [18F]MK-6240 SUVR. We found no group-based increase of [18F]MK-6240 brain uptake in patients scanned at least 2 years after a single TBI compared with healthy volunteers, which suggests that no NFTs are building up in the first years after a single TBI. Nonetheless, correlations with cognitive outcomes were found that warrant further investigation.

TDP43 pathology in chronic traumatic encephalopathy retinas

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with repetitive head trauma. Brain pathology in CTE is characterized by neuronal loss, gliosis, and a distinctive pattern of neuronal accumulation of hyper-phosphorylated tau (p-tau) and phospho-TDP43 (p-TDP43). Visual anomalies have been reported by patients with CTE, but the ocular pathology underlying these symptoms is unknown. We evaluated retinal pathology in post-mortem eyes collected from 8 contact sport athletes with brain autopsy-confirmed stage IV CTE and compared their findings to retinas from 8 control patients without CTE and with no known history of head injury. Pupil-optic nerve cross sections were prepared and stained with hematoxylin and eosin (H&E), p-tau, p-TDP43, and total TDP43 by immunohistochemistry. No significant retinal degeneration was observed in CTE eyes compared to control eyes by H&E. Strong cytoplasmic p-TDP43 and total TDP43 staining was found in 6/8 CTE eyes in a subset of inner nuclear layer interneurons (INL) of the retina, while only 1/8 control eyes showed similar p-TDP43 pathology. The morphology and location of these inner nuclear layer interneurons were most compatible with retinal horizontal cells, although other retinal cell types present in INL could not be ruled out. No p-tau pathology was observed in CTE or control retinas. These findings identify novel retinal TDP43 pathology in CTE retinas and support further investigation into the role of p-TDP43 in producing visual deficits in patients with CTE.

Athletes are not at greater risk for death by suicide: A review

INTRODUCTION

Suicide represents a major mental and public health issue. Elite athletes share certain individual and environmental characteristics that may increase their risk for mental illnesses, ultimately leading to suicide. This notion conflicts with the general perception of athletes, being the healthiest representatives of society.

METHODS

A comprehensive literature search was carried out through PubMed and Embase databases for relevant publications.

RESULTS

Recent calls for investigating suicidality among athletes resulted in a considerable amount of literature providing some evidence regarding lower rates of suicide among professional and high-performance athletes as well as similar incidence and prevalence of mental conditions, which are known as risk factors for suicide. Nevertheless, special attention is required in this population as predisposing and precipitating factors might differ from classical features of suicidality in the general population. Sports physicians, sports psychiatrists, and other mental health professionals in elite sports should be aware of early signs of affective disorders, risk of recreational drug abuse, misuse of performance-enhancing medications, sport-specific environmental stressors, serious physical injuries, and presence of physical or mental illness, all of which may increase suicidality. Traumatic brain injury (TBI) is with suicide with higher severity correlated with increased risk. Compared to active athletes, former athletes may have higher rates of suicide due to common life stressors occurring after sports retirement.

CONCLUSIONS

The findings suggest a multidisciplinary approach to suicidality in elite athletes, the main goal of which should be the reduction of suicide-related morbidity and mortality. Further research is required to clarify the existing gaps in the current knowledge of the issue. While having lower rates of suicide, athletes share some similar (affective disorders, drug abuse, mental and physical illness) and unique factors (misuse of performance-enhancing substances, sports-related stressors, sports injuries, TBI) putting them at risk of suicide during active career and retirement.

Information seeking behaviors and attitudes of wives of former football players regarding chronic traumatic encephalopathy

This study examines CTE-related knowledge and information-seeking behaviors of caregivers of persons who are at high risk of CTE. Online survey responses were collected from 64 females, ages 18-74, who were married to former college, semiprofessional, or professional football players and were fluent in English. Ranging from 0 to 18, a score was calculated to represent level of CTE knowledge. Participants were classified into groups based on their spouse's reported symptoms and diagnosis. Approximately 87% of participants reported that their spouses have been diagnosed with a football-related concussion and were significantly more likely to seek out information from a healthcare provider, a scientific journal or article, and post/comment on social media compared to spouses of symptomatic/undiagnosed and non-symptomatic groups. Participants reported 77% of available information as probably true, with social media thought to be highly credible. Highest levels of dissatisfaction were reported for league-sponsored websites and physicians/healthcare providers. Although the majority of participants sought CTE related information on regular or social media, and the internet, information sources differed amongst the groups. These findings may help healthcare providers and organizations develop more effective health-related educational programs that will help the wives make informed decisions regarding care for their spouses with respect to CTE.

Neuro-Inflammation Modulation and Post-Traumatic Brain Injury Lesions: From Bench to Bed-Side

Head trauma is the most common cause of disability in young adults. Known as a silent epidemic, it can cause a mosaic of symptoms, whether neurological (sensory-motor deficits), psychiatric (depressive and anxiety symptoms), or somatic (vertigo, tinnitus, phosphenes). Furthermore, cranial trauma (CT) in children presents several particularities in terms of epidemiology, mechanism, and physiopathology-notably linked to the attack of an immature organ. As in adults, head trauma in children can have lifelong repercussions and can cause social and family isolation, difficulties at school, and, later, socio-professional adversity. Improving management of the pre-hospital and rehabilitation course of these patients reduces secondary morbidity and mortality, but often not without long-term disability. One hypothesized contributor to this process is chronic neuroinflammation, which could accompany primary lesions and facilitate their development into tertiary lesions. Neuroinflammation is a complex process involving different actors such as glial cells (astrocytes, microglia, oligodendrocytes), the permeability of the blood-brain barrier, excitotoxicity, production of oxygen derivatives, cytokine release, tissue damage, and neuronal death. Several studies have investigated the effect of various treatments on the neuroinflammatory response in traumatic brain injury in vitro and in animal and human models. The aim of this review is to examine the various anti-inflammatory therapies that have been implemented.

Chronic Traumatic Encephalopathy in the Brains of Military Personnel

BACKGROUND

Persistent neuropsychiatric sequelae may develop in military personnel who are exposed to combat; such sequelae have been attributed in some cases to chronic traumatic encephalopathy (CTE). Only limited data regarding CTE in the brains of military service members are available.

METHODS

We performed neuropathological examinations for the presence of CTE in 225 consecutive brains from a brain bank dedicated to the study of deceased service members. In addition, we reviewed information obtained retrospectively regarding the decedents' histories of blast exposure, contact sports, other types of traumatic brain injury (TBI), and neuropsychiatric disorders.

RESULTS

Neuropathological findings of CTE were present in 10 of the 225 brains (4.4%) we examined; half the CTE cases had only a single pathognomonic lesion. Of the 45 brains from decedents who had a history of blast exposure, 3 had CTE, as compared with 7 of 180 brains from those without a history of blast exposure (relative risk, 1.71; 95% confidence interval [CI], 0.46 to 6.37); 3 of 21 brains from decedents with TBI from an injury during military service caused by the head striking a physical object without associated blast exposure (military impact TBI) had CTE, as compared with 7 of 204 without this exposure (relative risk, 4.16; 95% CI, 1.16 to 14.91). All brains with CTE were from decedents who had participated in contact sports; 10 of 60 contact-sports participants had CTE, as compared with 0 of 165 who had not participated in contact sports (point estimate of relative risk not computable; 95% CI, 6.16 to infinity). CTE was present in 8 of 44 brains from decedents with non-sports-related TBI in civilian life, as compared with 2 of 181 brains from those without such exposure in civilian life (relative risk, 16.45; 95% CI, 3.62 to 74.79).

CONCLUSIONS

Evidence of CTE was infrequently found in a series of brains from military personnel and was usually reflected by minimal neuropathologic changes. Risk ratios for CTE were numerically higher among decedents who had contact-sports exposure and other exposures to TBI in civilian life than among those who had blast exposure or other military TBI, but the small number of CTE cases and wide confidence intervals preclude causal conclusions. (Funded by the Department of Defense-Uniformed Services University Brain Tissue Repository and Neuropathology Program and the Henry M. Jackson Foundation for the Advancement of Military Medicine.).

High School Football and Risk for Depression and Suicidality in Adulthood: Findings From a National Longitudinal Study

BACKGROUND

There is growing public concern regarding the potential long-term effects of playing football on brain health, specifically that playing football before and during high school might cause damage to the brain that manifests years or decades later as depression or suicidality. This study examined if playing high school football was associated with increased lifetime risk for depression, suicidality over the past year, or depressed mood in the past week in men aged between their middle 30 s to early 40 s.

METHODS

Publicly available data from the National Longitudinal Study of Adolescent to Adult Health were analyzed. This longitudinal, prospective cohort study sampled nationally representative U.S. youth starting in 1994-1995 (Wave I) and most recently in 2016-2018 (Wave V). A total of 3,147 boys participated in Wave I (median age = 15), of whom 1,805 were re-assessed during Wave V (median age = 38).

RESULTS

Of the 1,762 men included in the study, 307 (17.4%) men reported being diagnosed with depression and 275 (15.6%) reported being diagnosed with an anxiety disorder or panic disorder at some point in their life. When comparing men who played high school football to those who did not, there were no differences in the proportions of the sample who had a lifetime diagnosis of depression, lifetime diagnosis of anxiety/panic disorders, suicidal ideation in the past year, psychological counseling in the past year, or current depressed mood. However, men who received psychological counseling and/or experienced suicidal ideation during adolescence were significantly more likely to report a lifetime history of depression, suicidal ideation in the past year, and current depressed mood.

CONCLUSION

Individuals who reported playing football during adolescence did not have an increased risk of depression or suicidal ideation when they were in their middle 30 s to early 40 s, but mental health problems during adolescence were associated with an increased risk for psychological health difficulties more than 20 years later.

Suicide in Older Adult Men Is Not Related to a Personal History of Participation in Football

Introduction: It is reasonable to estimate that tens of millions of men in the United States played high school football. There is societal concern that participation in football confers risk for later-in-life mental health problems. The purpose of this study is to examine whether there is an association between a personal history of playing high school football and death by suicide. Methods: The subjects were obtained from the Lieber Institute for Brain Development (LIBD) brain donation program in collaboration with the Office of the Medical Examiner at Western Michigan University Homer Stryker MD School of Medicine. Donor history was documented via medical records, mental health records, and telephone interviews with the next-of-kin. Results: The sample included 198 men aged 50 or older (median = 65.0 years, interquartile range = 57-75). There were 34.8% who participated in contact sports during high school (including football), and 29.8% participated in high school football. Approximately one-third of the sample had suicide as their manner of death (34.8%). There was no statistically significant difference in the proportions of suicide as a manner of death among those men with a personal history of playing football compared to men who did not play football or who did not play sports (p = 0.070, Odds Ratio, OR = 0.537). Those who played football were significantly less likely to have a lifetime history of a suicide attempt (p = 0.012, OR = 0.352). Men with mood disorders (p < 0.001, OR = 10.712), substance use disorders (p < 0.020, OR = 2.075), and those with a history of suicide ideation (p < 0.001, OR = 8.038) or attempts (p < 0.001, OR = 40.634) were more likely to have suicide as a manner of death. Moreover, those men with a family history of suicide were more likely to have prior suicide attempts (p = 0.031, OR = 2.153) and to have completed suicide (p = 0.001, OR = 2.927). Discussion: Suicide was related to well-established risk factors such as a personal history of a mood disorder, substance abuse disorder, prior suicide ideation, suicide attempts, and a family history of suicide attempts. This study adds to a steadily growing body of evidence suggesting that playing high school football is not associated with increased risk for suicidality or suicide during adulthood.

Traumatic Brain Injury and Risk of Dementia and Alzheimer's Disease: A Systematic Review and Meta-Analysis

INTRODUCTION

Previous studies have investigated the potential role of traumatic brain injury (TBI) in subsequent development of dementia and Alzheimer's disease (AD) but reported inconsistent results. We aim to determine the association between TBI and subsequent occurrence of dementia and AD.

METHODS

We performed a systematic search in PubMed and Web of Science for studies that quantitatively investigated the association between TBI and risk of dementia and AD and were published on or before September 21, 2021. A random-effect model was used to combine the estimates.

RESULTS

Twenty-five eligible articles were included in this meta-analysis. The results suggested that TBI was associated with an increased risk of dementia (pooled odds ratio [OR] = 1.81, 95% confidence interval [CI] = 1.53 - 2.14). However, no association was observed between TBI and Alzheimer's disease (pooled OR = 1.02, 95% CI = 0.91 - 1.15). In the subgroup analysis, TBI with loss of consciousness was not associated with risk of dementia (pooled OR = 0.96, 95% CI = 0.84 - 1.09). Besides, Asian ethnicity, male gender, and mean age of the participants less than 65 were associated with a higher risk of dementia.

CONCLUSION

Our study suggests an increased risk of dementia among individuals with TBI, highlighting the need for more intensive medical monitoring and health education in individuals with TBI. Biological mechanisms linking TBI and the development of dementia are needed in future studies.

Playing High School Football Is Not Associated With an Increased Risk for Suicidality in Early Adulthood

OBJECTIVE

To determine if playing high school football is associated with suicide ideation between the ages of 24 and 32 years.

DESIGN

Data were analyzed from the National Longitudinal Study of Adolescent to Adult Health. This prospective cohort study sampled nationally representative US participants at 4 time points from 1994 to 2008.

SETTING

In-home assessment.

PARTICIPANTS

There were 3147 boys (age: median = 14.9, SD = 1.8) who participated during adolescence in 1994 to 1995 (wave I), of whom 2353 were reinterviewed in 2008 (wave IV, age: median = 29.1, SD = 1.8).

ASSESSMENT OF RISK FACTORS

Football participation, history of psychological counseling, suicide ideation, and a suicide attempt in the past year during high school.

MAIN OUTCOME MEASURES

Lifetime history of depression, suicide ideation within the past year, and feeling depressed in the past 7 days at wave IV.

RESULTS

Men who played high school football, compared with those who did not, reported similar rates of lifetime diagnosis of depression, suicide ideation in the past year, and feeling depressed in the past 7 days. Those who played football reported similar rates of suicide ideation in the past year when they were in their early 20s. Individuals who underwent psychological counseling during adolescence were more likely to report a lifetime history of depression and suicide ideation in the past year.

CONCLUSIONS

Young men who played high school football are not at an increased risk for suicide ideation during both their early 20s and late 20s. By contrast, those who experienced mental health problems in high school were much more likely to experience suicide ideation during their 20s.

Cellular Senescence in Traumatic Brain Injury: Evidence and Perspectives

Mild traumatic brain injury (mTBI) can lead to long-term neurological dysfunction and increase one's risk of neurodegenerative disease. Several repercussions of mTBI have been identified and well-studied, including neuroinflammation, gliosis, microgliosis, excitotoxicity, and proteinopathy – however the pathophysiological mechanisms activating these pathways after mTBI remains controversial and unclear. Emerging research suggests DNA damage-induced cellular senescence as a possible driver of mTBI-related sequalae. Cellular senescence is a state of chronic cell-cycle arrest and inflammation associated with physiological aging, mood disorders, dementia, and various neurodegenerative pathologies. This narrative review evaluates the existing studies which identify DNA damage or cellular senescence after TBI (including mild, moderate, and severe TBI) in both experimental animal models and human studies, and outlines how cellular senescence may functionally explain both the molecular and clinical manifestations of TBI. Studies on this subject clearly show accumulation of various forms of DNA damage (including oxidative damage, single-strand breaks, and double-strand breaks) and senescent cells after TBI, and indicate that cellular senescence may be an early event after TBI. Further studies are required to understand the role of sex, cell-type specific mechanisms, and temporal patterns, as senescence may be a pathway of interest to target for therapeutic purposes including prognosis and treatment.

Distribution of Head Acceleration Events Varies by Position and Play Type in North American Football

OBJECTIVE

The goal of this pilot study was to evaluate the number of head acceleration events (HAEs) based on position, play type, and starting stance.

DESIGN

Prospective cohort study.

SETTING

Postcollegiate skill development camp during practice sessions and 1 exhibition game.

PARTICIPANTS

Seventy-eight male adult North American football athletes.

INDEPENDENT VARIABLES

A position was assigned to each participant, and plays in the exhibition game were separated by play type for analysis. During the exhibition game, video data were used to determine the effects of the starting position ("up" in a 2-point stance or "down" in a 3- or 4-point stance) on the HAEs experienced by players on the offensive line.

MAIN OUTCOME MEASURES

Peak linear acceleration and number of HAEs greater than 20 g (g = 9.81 m/s2) were measured using an xPatch (X2 Biosystems, Seattle, WA).

RESULTS

Four hundred thirty-seven HAEs were recorded during practices and 272 recorded during the exhibition game; 98 and 52 HAEs, the greatest number of HAEs by position in the game, were experienced by the offensive and defensive linemen, respectively. Linebackers and tight ends experienced high percentages of HAEs above 60 g. Offensive line players in a down stance had a higher likelihood of sustaining a HAE than players in an up stance regardless of the type of play (run vs pass).

CONCLUSIONS

Changing the stance of players on the offensive line and reducing the number of full-contact practices will lower HAEs.

Concussion/Mild Traumatic Brain Injury (TBI) Induces Brain Insulin Resistance: A Positron Emission Tomography (PET) Scanning Study

Brain injury/concussion is a growing epidemic throughout the world. Although evidence supports association between traumatic brain injury (TBI) and disturbance in brain glucose metabolism, the underlying molecular mechanisms are not well established. Previously, we reported the release of cellular prion protein (PrPc) from the brain to circulation following TBI. The PrPc level was also found to be decreased in insulin-resistant rat brains. In the present study, we investigated the molecular link between PrPc and brain insulin resistance in a single and repeated mild TBI-induced mouse model. Mild TBI was induced in mice by dropping a weight (~95 g at 1 m high) on the right side of the head. The procedure was performed once and thrice (once daily) for single (SI) and repeated induction (RI), respectively. Micro PET/CT imaging revealed that RI mice showed significant reduction in cortical, hippocampal and cerebellum glucose uptake compared to SI and control. Mice that received RI also showed significant motor and cognitive deficits. In co-immunoprecipitation, the interaction between PrPc, flotillin and Cbl-associated protein (CAP) observed in the control mice brains was disrupted by RI. Lipid raft isolation showed decreased levels of PrPc, flotillin and CAP in the RI mice brains. Based on observation, it is clear that PrPc has an interaction with CAP and the dislodgment of PrPc from cell membranes may lead to brain insulin resistance in a mild TBI mouse model. The present study generated a new insight into the pathogenesis of brain injury, which may result in the development of novel therapy.

Association of Position Played and Career Duration and Chronic Traumatic Encephalopathy at Autopsy in Elite Football and Hockey Players

OBJECTIVE

To determine whether an association exists between career duration or position played and the presence of chronic traumatic encephalopathy (CTE) at autopsy in a series of elite football and hockey players.

METHODS

This retrospective cohort study analyzed postmortem brains of 35 former football or hockey players (29 professional, 6 university varsity/major junior), with the presence of CTE at autopsy as the primary outcome. Position played (highest level), age at retirement (indicator of lifetime exposure to sport), and hockey fighting/penalization histories (surrogate marker for role/style of play) were collected. A blinded neuropathologic evaluation of each participant was performed, providing an assessment for neurodegenerative diseases including CTE, based on the 2015 National Institute of Neurological Disorders and Stroke/National Institute of Biomedical Imaging and Bioengineeringconsensus paper.

RESULTS

In total, 17 of 35 former players (48.6%) showed pathologic evidence of CTE. There was no correlation found between position played and CTE presence, nor between hockey fighting/penalization histories and CTE, in either the football or hockey groups (p > 0.75, Mann-Whitney-Wilcoxon). Similarly, there was no association between age at retirement and CTE presence (p > 0.5, Mann-Whitney-Wilcoxon). In 24 of 35 cases (68.6%), other neuropathologies were present, 13 of 24 (54.2%) of which were coexistent with CTE.

CONCLUSION

In this cohort of 35 former collision sports athletes, no significant associations were found between career duration, position or role played, and CTE presence at autopsy. Although limited by the small and nonrepresentative sample studied, these findings suggest that nonsport factors may be important to understand differing susceptibilities among athletes to CTE.

Predictors and Correlates of Depression in Retired Elite Level Rugby League Players

Background: There is considerable interest in determining whether later-in-life depression is associated with lifetime history of concussions or the duration of a career in professional contact and collision sports. Rugby league is a high-intensity collision sport involving a large number of tackles per game and a high rate of concussions. We examined predictors and correlates of depression in retired elite level rugby league players in Australia. Methods: Retired elite level rugby league players (N = 141, age: M = 52.6, SD = 13.8; Range = 30-89 years) completed the Depression, Anxiety, and Stress Scale (DASS), Brief Pain Inventory, Connor-Davidson Resilience Scale (CD-RISC), and Epworth Sleepiness Scale; they also reported on lifetime history of concussions. The DASS depression score was regressed on age, total number of self-reported concussions, years played professionally, CD-RISC score, BPI pain interference score, and ESS score. Results: The retired players reported a median of 15 total lifetime concussions [interquartile range (IQR) = 6-30], and a median of 8 years playing professional sports (IQR = 3.5-11). The proportion of the sample endorsing at least mild current depression was 29%. The DASS depression score was positively correlated with the DASS anxiety (r = 0.54) and DASS stress scores (r = 0.58). The CD-RISC score was negatively correlated with the depression score (r = -0.53). Depression scores were not significantly correlated with pain severity (r = 0.14), and were weakly correlated with life interference due to pain (r = 0.20) and years playing professional sports (r = -0.17). Depression scores were not significantly correlated with lifetime history of concussions (r = 0.14). A multiple regression model, with age, total number of self-reported concussions, years played professionally, the CD-RISC, Brief Pain Inventory-pain interference score, and Epworth Sleepiness Scale score as predictors was significant, with 35% of the variance in DASS depression accounted for. The two significant independent predictors of depression were lower resilience and greater life interference due to pain. Conclusions: This is the first large study of depression in retired rugby league players. Depression in these retired players was not meaningfully associated with lifetime history of concussions or number of years playing elite level collision sport. Depression was associated with current anxiety, stress, resilience, and life interference due to chronic pain.

Effects of purposeful soccer heading on circulating small extracellular vesicle concentration and cargo

BACKGROUND

Considering the potential cumulative effects of repetitive head impact (HI) exposure, we need sensitive biomarkers to track short- and long-term effects. Circulating small extracellular vesicles (sEVs) (<200 nm) traffic biological molecules throughout the body and may have diagnostic value as biomarkers for disease. The purpose of this study was to identify the microRNA (miRNA) profile in circulating sEVs derived from human plasma following repetitive HI exposure.

METHODS

Healthy adult (aged 18-35 years) soccer players were randomly assigned to one of 3 groups: the HI group performed 10 standing headers, the leg impact group performed 10 soccer ball trapping maneuvers over 10 min, and the control group did not participate in any soccer drills. Plasma was collected before testing and 24 h afterward, and sEVs were isolated and characterized via nanoparticle tracking analysis. Next-generation sequencing was utilized to identify candidate miRNAs isolated from sEVs, and candidate microRNAs were analyzed via quantitative polymerase chain reaction. In silico target prediction was performed using TargetScan (Version 7.0; targetscan.org) and miRWalk (http://mirwalk.umm.uni-heidelberg.de/) programs, and target validation was performed using luciferase reporter vectors with a miR-7844-5p mimic in human embryonic kidney (HEK) 293T/17 cells.

RESULTS

Plasma sEV concentration and size were not affected across time and group following repetitive HI exposure. After 24 h, the HI read count from next-generation sequencing showed a 4-fold or greater increase in miR-92b-5p, miR-423-5p, and miR-24-3p and a 3-fold or greater decrease in miR-7844-5p, miR-144-5p, miR-221-5p, and miR-22-3p. Analysis of quantitative polymerase chain reaction revealed that leg impact did not alter the candidate miRNA levels. To our knowledge, miR-7844-5p is a previously unknown miRNA. We identified 8 miR-7844-5p mRNA targets: protein phosphatase 1 regulatory inhibitor subunit 1B (PPP1R1B), LIM and senescent cell antigen-like domains 1 (LIMS1), autophagy-related 12 (ATG12), microtubule-associated protein 1 light chain 3 beta (MAP1LC3B), integrin subunit alpha-1 (ITGA1), mitogen-activated protein kinase 1 (MAPK1), glycogen synthase kinase 3β (GSK3β), and mitogen-activated protein kinase 8 (MAPK8).

CONCLUSION

Collectively, these data indicate repetitive HI exposure alters plasma sEV miRNA content, but not sEV size or number. Furthermore, for the first time we demonstrate that previously unknown miR-7844-5p targets mRNAs known to be involved in mitochondrial apoptosis, autophagy regulation, mood disorders, and neurodegenerative disease.

Transplanting Rac1-silenced bone marrow mesenchymal stem cells promote neurological function recovery in TBI mice

Bone marrow mesenchymal stem cells (BMMSCs)-based therapy has emerged as a promising novel therapy for Traumatic Brain Injury (TBI). However, the therapeutic quantity of viable implanted BMMSCs necessary to initiate efficacy is still undetermined. Increased oxidative stress following TBI, which leads to the activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase signaling pathway, has been implicated in accounting for the diminished graft survival and therapeutic effect. To prove this assertion, we silenced the expression of NADPH subunits (p22-phox, p47-phox, and p67-phox) and small GTPase Rac1 in BMMSCs using shRNA. Our results showed that silencing these proteins significantly reduced oxidative stress and cell death/apoptosis, and promoted implanted BMMSCs proliferation after TBI. The most significant result was however seen with Rac1 silencing, which demonstrated decreased expression of apoptotic proteins, enhanced in vitro survival ratio, reduction in TBI lesional volume and significant improvement in neurological function post shRac1-BMMSCs transplantation. Additionally, two RNA-seq hub genes (VEGFA and MMP-2) were identified to play critical roles in shRac1-mediated cell survival. In summary, we propose that knockdown of Rac1 gene could significantly boost cell survival and promote the recovery of neurological functions after BMMSCs transplantation in TBI mice.

Gamma entrainment frequency affects mood, memory and cognition: an exploratory pilot study

Here we provide evidence with an exploratory pilot study that through the use of a Gamma 40 Hz entrainment frequency, mood, memory and cognition can be improved with respect to a 9-participant cohort. Participants constituted towards three binaural entrainment frequency groups: the 40 Hz, 25 Hz and 100 Hz. Participants attended a total of eight entrainment frequency sessions twice over the duration of a 4-week period. Additionally, participants were assessed based on their cognitive abilities, mood as well as memory, where the cognitive and memory assessments occurred before and after a 5-min binaural beat stimulation. The mood assessment scores were collected from sessions 1, 4 and 8, respectively. With respect to the Gamma 40 Hz entrainment frequency population, we observed a mean improvement in cognitive scores, elevating from 75% average to 85% average upon conclusion of the experimentation at weak statistical significance ([Formula: see text] = 0.10, p = 0.076). Similarly, memory score improvements at a greater significance ([Formula: see text] = 0.05, p = 0.0027) were noted, elevating from an average of 87% to 95%. In pertinence to the mood scores, a negative correlation across all populations were noted, inferring an overall increase in mood due to lower scores correlating with elevated mood. Finally, correlation analysis revealed a stronger R[Formula: see text] value (0.9838) within the 40 Hz group between sessions as well as mood score when compared across the entire frequency group cohort.

Head acceleration event metrics in youth contact sports more dependent on sport than level of play

The goal of the study was to evaluate how repetitive head traumas sustained by athletes in contact sports depend on sport and level of play. A total of 16 middle school football players, 107 high school football players, and 65 high school female soccer players participated. Players were separated into levels of play: middle school (MS), freshman (FR), junior varsity (JV), junior varsity-varsity (JV-V), and varsity (V). xPatch sensors were used to measure peak translational and angular accelerations (PTA and PAA, respectively) for each head acceleration event (HAE) during practice and game sessions. Data were analyzed using a custom MATLAB program to compare metrics that have been correlated with functional neurological changes: session metrics (median HAEs per contact session), season metrics (total HAEs, cumulative PTA/PAA), and regressions (cumulative PTA/PAA versus total HAEs, total HAEs versus median HAEs per contact session). Football players had greater session (p<.001) and season (p<.001) metrics than soccer players, but soccer players had a significantly greater player average PAA per HAE than football players (p<.001). Middle school football players had similar session and season metrics to high school level athletes. In conclusion, sport has a greater influence on HAE characteristics than level of play.

Does Mild Traumatic Brain Injury Increase the Risk for Dementia? A Systematic Review and Meta-Analysis

Background: Mild traumatic brain injury (mTBI) is a putative risk factor for dementia; however, despite having apparent face validity, the evidence supporting this hypothesis remains inconclusive. Understanding the role of mTBI as a risk factor is becoming increasingly important given the high prevalence of mTBI, and the increasing societal burden of dementia. Objective: Our objective was to use the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) format to determine if an association exists between mTBI and dementia and related factors, and to quantify the degree of risk. Methods: In this format, two authors conducted independent database searches of PubMed, PsycInfo, and CINAHL using three search blocks to find relevant papers published between 2000 and 2020. Relevant studies were selected using pre-defined inclusion/exclusion criteria, and bias scoring was performed independently by the two authors before a subset of studies was selected for meta-analysis. Twenty-one studies met the inclusion criteria for this systematic review. Results: The meta-analysis yielded a pooled odds ratio of 1.96 (95% CI 1.698–2.263), meaning individuals were 1.96 times more likely to be diagnosed with dementia if they had a prior mTBI. Most studies examining neuropsychiatric and neuroimaging correlates of dementia found subtle, persistent changes after mTBI. Conclusion: These results indicate that mTBI is a risk factor for the development of dementia and causes subtle changes in performance on neuropsychiatric testing and brain structure in some patients.

Retired National Football League Players are Not at Greater Risk for Suicide

Objective

Some researchers have claimed that former National Football League (NFL) players are at increased risk for suicide as a clinical feature of chronic traumatic encephalopathy (CTE). This review examines the literature on risk for suicide in former professional football players, and the association between suicide and CTE.

Method

A narrative review of the literature published between 1928 and 2018.

Results

Between 1928 and 2009, suicide was not considered to be a clinical feature of CTE in the literature. The best available evidence from epidemiological studies suggests that former NFL football players are at lesser risk for suicide, not greater risk, compared to men in the general population. However, surveys have revealed that a substantial minority of former NFL players have depression and other mental health problems, chronic pain and opioid use is relatively common, and those with depression and chronic pain also have greater life stress and financial difficulties. That minority would be at increased risk for suicidal thoughts and behaviors.

Conclusions

Researchers and clinicians are encouraged to be cautious and circumspect when considering the clinical presentation of former athletes, and to not assume that depression and suicidality are caused by specific types of neuropathology. This represents a reductionistic and Procrustean view. Some former football players have mental health problems, but it should not be assumed uncritically that the underlying cause is an inexorably progressive neurodegenerative disease. Providing evidence-informed and evidence-supported treatments for depression and suicidality might reduce suffering and improve their functioning.

Chronic Traumatic Encephalopathy: A Comparison with Alzheimer's Disease and Frontotemporal Dementia

The clinical diagnosis of chronic traumatic encephalopathy (CTE) is challenging due to heterogeneous clinical presentations and overlap with other neurodegenerative dementias. Depending on the clinical presentation, the differential diagnosis of CTE includes Alzheimer's disease (AD), behavioral variant frontotemporal dementia (bvFTD), Parkinson's disease, amyotrophic lateral sclerosis, primary mood disorders, posttraumatic stress disorder, and psychotic disorders. The aim of this article is to compare the clinical aspects, genetics, fluid biomarkers, imaging, treatment, and pathology of CTE to those of AD and bvFTD. A detailed clinical evaluation, neurocognitive assessment, and structural brain imaging can inform the differential diagnosis, while molecular biomarkers can help exclude underlying AD pathology. Prospective studies that include clinicopathological correlations are needed to establish tools that can more accurately determine the cause of neuropsychiatric decline in patients at risk for CTE.

Concussion in soccer: a comprehensive review of the literature

Sports-related concussion has been examined extensively in collision sports such as football and hockey. However, historically, lower-risk contact sports such as soccer have only more recently garnered increased attention. Here, we review articles examining the epidemiology, injury mechanisms, sex differences, as well as the neurochemical, neurostructural and neurocognitive changes associated with soccer-related concussion. From 436 titles and abstracts, 121 full texts were reviewed with a total of 64 articles identified for inclusion. Concussion rates are higher during competitions and in female athletes with purposeful heading rarely resulting in concussion. Given a lack of high-level studies examining sports-related concussion in soccer, clinicians and scientists must focus research efforts on large-scale data gathering and development of improved technologies to better detect and understand concussion.

Tau immunophenotypes in chronic traumatic encephalopathy recapitulate those of ageing and Alzheimer's disease

Traumatic brain injury (TBI) is a risk factor for neurodegenerative disease, including chronic traumatic encephalopathy (CTE). Preliminary consensus criteria define the pathognomonic lesion of CTE as patchy tau pathology within neurons and astrocytes at the depths of cortical sulci. However, the specific tau isoform composition and post-translational modifications in CTE remain largely unexplored. Using immunohistochemistry, we performed tau phenotyping of CTE neuropathologies and compared this to a range of tau pathologies, including Alzheimer's disease, primary age-related tauopathy, ageing-related tau astrogliopathy and multiple subtypes of frontotemporal lobar degeneration with tau inclusions. Cases satisfying preliminary consensus diagnostic criteria for CTE neuropathological change (CTE-NC) were identified (athletes, n = 10; long-term survivors of moderate or severe TBI, n = 4) from the Glasgow TBI Archive and Penn Neurodegenerative Disease Brain Bank. In addition, material from a range of autopsy-proven ageing-associated and primary tauopathies in which there was no known history of exposure to TBI was selected as non-injured controls (n = 32). Each case was then stained with a panel of tau antibodies specific for phospho-epitopes (PHF1, CP13, AT100, pS262), microtubule-binding repeat domains (3R, 4R), truncation (Tau-C3) or conformation (GT-7, GT-38) and the extent and distribution of staining assessed. Cell types were confirmed with double immunofluorescent labelling. Results demonstrate that astroglial tau pathology in CTE is composed of 4R-immunoreactive thorn-shaped astrocytes, echoing the morphology and immunophenotype of astrocytes encountered in ageing-related tau astrogliopathy. In contrast, neurofibrillary tangles of CTE contain both 3R and 4R tau, with post-translational modifications and conformations consistent with Alzheimer's disease and primary age-related tauopathy. Our observations establish that the astroglial and neurofibrillary tau pathologies of CTE are phenotypically distinct from each other and recapitulate the tau immunophenotypes encountered in ageing and Alzheimer's disease. As such, the immunohistochemical distinction of CTE neuropathology from other mixed 3R/4R tauopathies of Alzheimer's disease and ageing may rest solely on the pattern and distribution of pathology.

Anger and Depression in Middle-Aged Men: Implications for a Clinical Diagnosis of Chronic Traumatic Encephalopathy

OBJECTIVE

In recent years, it has been proposed that problems with anger control and depression define clinical features of chronic traumatic encephalopathy (CTE). The authors examined anger problems and depression in middle-aged men from the general population and related those findings to the proposed clinical criteria for CTE.

METHODS

A sample of 166 community-dwelling men ages 40-60 was extracted from the normative database of the National Institutes of Health Toolbox. All participants denied prior head injury or traumatic brain injury (TBI). Participants completed scales assessing anger, hostility, aggression, anxiety, and depression.

RESULTS

In response to the item "I felt angry," 21.1% of men reported "sometimes," and 4.8% reported "often." When asked "If I am provoked enough I may hit another person," 11.4% endorsed the statement as true. There were moderate correlations between anger and anxiety (Spearman's ρ=0.61) and between depression and affective anger (ρ=0.51), hostility (ρ=0.56), and perceived hostility (ρ=0.35). Participants were dichotomized into a possible depression group (N=49) and a no-depression group (N=117) on the basis of the question "I feel depressed," specific to the past 7 days. The possible depression group reported higher anxiety (p<0.001, Cohen's d=1.51), anger (p<0.001, Cohen's d=0.96), and hostility (p<0.001, Cohen's d=0.95).

CONCLUSIONS

Some degree of anger and aggression are reported by a sizable minority of middle-aged men in the general population with no known history of TBI. Anger and hostility are correlated with depression and anxiety, indicating that all tend to co-occur. The base rates and comorbidity of affective dysregulation in men in the general population is important to consider when conceptualizing CTE phenotypes.

A novel repetitive head impact exposure measurement tool differentiates player position in National Football League

American-style football participation poses a high risk of repetitive head impact (RHI) exposure leading to acute and chronic brain injury. The complex nature of symptom expression, human predisposition, and neurological consequences of RHI limits our understanding of what constitutes as an injurious impact affecting the integrity of brain tissue. Video footage of professional football games was reviewed and documentation made of all head contact. Frequency of impact, tissue strain magnitude, and time interval between impacts was used to quantify RHI exposure, specific to player field position. Differences in exposure characteristics were found between eight different positions; where three unique profiles can be observed. Exposure profiles provide interpretation of the relationship between the traumatic event(s) and how tissue injury is manifested and expressed. This study illustrates and captures an objective measurement of RHI on the field, a critical component in guiding public policy and guidelines for managing exposure.

RhoA-ROCK Signaling as a Therapeutic Target in Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. TBIs, which range in severity from mild to severe, occur when a traumatic event, such as a fall, a traffic accident, or a blow, causes the brain to move rapidly within the skull, resulting in damage. Long-term consequences of TBI can include motor and cognitive deficits and emotional disturbances that result in a reduced quality of life and work productivity. Recovery from TBI can be challenging due to a lack of effective treatment options for repairing TBI-induced neural damage and alleviating functional impairments. Central nervous system (CNS) injury and disease are known to induce the activation of the small GTPase RhoA and its downstream effector Rho kinase (ROCK). Activation of this signaling pathway promotes cell death and the retraction and loss of neural processes and synapses, which mediate information flow and storage in the brain. Thus, inhibiting RhoA-ROCK signaling has emerged as a promising approach for treating CNS disorders. In this review, we discuss targeting the RhoA-ROCK pathway as a therapeutic strategy for treating TBI and summarize the recent advances in the development of RhoA-ROCK inhibitors.

Association between contact sports participation and chronic traumatic encephalopathy: a retrospective cohort study

Chronic traumatic encephalopathy is a debilitating neurodegenerative disorder associated with repetitive traumatic brain injuries often sustained through prior contact sport participation. The frequency of this disorder in a diverse population, including amateur athletes, is unknown. Primary historical obituary and yearbook records were queried for 2566 autopsy cases in the Mayo Clinic Tissue Registry resulting in identification of 300 former athletes and 450 non-athletes. In these cases, neocortical tissue was screened for tau pathology with immunohistochemistry, including pathology consistent with chronic traumatic encephalopathy, blinded to exposure or demographic information. Using research infrastructure of the Rochester Epidemiology Project, a comprehensive and established medical records-linkage system of care providers in southern Minnesota and western Wisconsin, medical diagnostic billing codes pertaining to head trauma, dementia, movement disorders, substance abuse disorders and psychiatric disorders were recorded for cases and controls in a blinded manner. A total of 42 individuals had pathology consistent with, or features of, chronic traumatic encephalopathy. It was more frequent in athletes compared to non-athletes (27 cases versus 15 cases) and was largely observed in men (except for one woman). For contact sports, American football had the highest frequency of chronic traumatic encephalopathy pathology (15% of cases) and an odds ratio of 2.62 (P-value = 0.005). Cases with chronic traumatic encephalopathy pathology had higher frequencies of antemortem clinical features of dementia, psychosis, movement disorders and alcohol abuse compared to cases without chronic traumatic encephalopathy pathology. Understanding the frequency of chronic traumatic encephalopathy pathology in a large autopsy cohort with diverse exposure backgrounds provides a baseline for future prospective studies assessing the epidemiology and public health impact of chronic traumatic encephalopathy and sports-related repetitive head trauma.

DNA repair deficiency and senescence in concussed professional athletes involved in contact sports

Mild traumatic brain injury (mTBI) leads to diverse symptoms including mood disorders, cognitive decline, and behavioral changes. In some individuals, these symptoms become chronic and persist in the long-term and can confer an increased risk of neurodegenerative disease and dementia diagnosis later in life. Despite the severity of its consequences, the pathophysiological mechanism of mTBI remains unknown. In this post-mortem case series, we assessed DNA damage-induced cellular senescence pathways in 38 professional athletes with a history of repeated mTBI and ten controls with no mTBI history. We assessed clinical presentation, neuropathological changes, load of DNA damage, morphological markers of cellular senescence, and expression of genes involved in DNA damage signaling, DNA repair, and cellular senescence including the senescence-associated secretory phenotype (SASP). Twenty-eight brains with past history of repeated mTBI history had DNA damage within ependymal cells, astrocytes, and oligodendrocytes. DNA damage burden was increased in brains with proteinopathy compared to those without. Cases also showed hallmark features of cellular senescence in glial cells including astrocytic swelling, beading of glial cell processes, loss of H3K27Me3 (trimethylation at lysine 27 of histone H3) and lamin B1 expression, and increased expression of cellular senescence and SASP pathways. Neurons showed a spectrum of changes including loss of emerin nuclear membrane expression, loss of Brahma-related gene-1 (BRG1 or SMARCA4) expression, loss of myelin basic protein (MBP) axonal expression, and translocation of intranuclear tau to the cytoplasm. Expression of DNA repair proteins was decreased in mTBI brains. mTBI brains showed substantial evidence of DNA damage and cellular senescence. Decreased expression of DNA repair genes suggests inefficient DNA repair pathways in this cohort, conferring susceptibly to cellular senescence and subsequent brain dysfunction after mTBI. We therefore suggest that brains of contact-sports athletes are characterized by deficient DNA repair and DNA damage-induced cellular senescence and propose that this may affect neurons and be the driver of brain dysfunction in mTBI, predisposing the progression to neurodegenerative diseases. This study provides novel targets for diagnostic and prognostic biomarkers, and represents viable targets for future treatments.

Word-reading ability as a "hold test" in cognitively normal young adults with history of concussion and repetitive head impact exposure: A CARE Consortium Study

Objective: Neuropsychological evaluations include hold tests like word-reading ability as estimates of premorbid intellect thought to be resilient to the effects of neurologic insult. We tested the alternative hypothesis that exposure to concussion or repetitive subclinical head impacts throughout early life may stunt acquisition of word-reading skills.Method: Data were obtained from student-athletes within the CARE Consortium that completed the Wechsler Test of Adult Reading (WTAR). Measures of head trauma burden included self-reported concussion history and cumulative years of exposure to collision sports. We evaluated the effects of head trauma, sociodemographic (race, SES), and academic (SAT/ACT scores, learning disorder) variables on WTAR standard score using linear regression. Analyses were repeated in a football-only subsample estimating age of first exposure to football as a predictor.Results: We analyzed data from 6,598 participants (72.2% white, 39.6% female, mean ± SD age = 18.8 ± 1.2 years). Head trauma variables collectively explained 0.1% of the variance in WTAR standard scores, with years of collision sport exposure weakly predicting lower WTAR standard scores (β = .026-.035, very small effect). In contrast, sociodemographic and academic variables collectively explained 20.9-22.5% of WTAR standard score variance, with strongest effects noted for SAT/ACT scores (β = .313-.337, medium effect), LD diagnosis (β = -.115 to -.131, small effect), and SES (β = .101-.108, small effect). Age of first exposure to football did not affect WTAR scores in a football-only sample.Conclusion: Wechsler Test of Adult Reading performance appears unrelated to history of self-reported concussion(s) and/or repetitive subclinical head trauma exposure in current collegiate athletes. Sociodemographic and academic variables should be incorporated in test score interpretations for diverse populations like athletes.

Dietary Supplementation With the Ketogenic Diet Metabolite Beta-Hydroxybutyrate Ameliorates Post-TBI Aggression in Young-Adult Male Drosophila

Traumatic brain injury (TBI), caused by repeated concussive head trauma can induce chronic traumatic encephalopathy (CTE), a neurodegenerative disease featuring behavioral symptoms ranging from cognitive deficits to elevated aggression. In a Drosophila model, we used a high-impact trauma device (Katzenberger et al., 2013, 2015) to induce TBI-like symptoms and to study post-TBI behavioral outcomes. Following TBI, aggression in banged male flies was significantly elevated as compared with that in unbanged flies. These increases in aggressive behavior were not the result of basal motility changes, as measured by a negative geotaxis assay. In addition, the increase in post-TBI aggression appeared to be specific to concussive trauma: neither cold exposure nor electric shock-two alternate types of trauma-significantly elevated aggressive behavior in male-male pairs. Various forms of dietary therapy, especially the high-fat, low-carbohydrate ketogenic diet (KD), have recently been explored for a wide variety of neuropathies. We thus hypothesized that putatively neuroprotective dietary interventions might be able to suppress post-traumatic elevations in aggressive behavior in animals subjected to head-trauma-inducing strikes, or "bangs". We supplemented a normal high-carbohydrate Drosophila diet with the KD metabolite beta-hydroxybutyrate (β-HB)-a ketone body (KB). Banged flies raised on a KB-supplemented diet exhibited a marked reduction in aggression, whereas aggression in unbanged flies was equivalent whether dieted with KB supplements or not. Pharmacological blockade of the ATP-sensitive potassium (KATP) channel abrogated KB effects reducing post-TBI aggression while pharmacological activation mimicked them, suggesting a mechanism by which KBs act in this model. KBs did not significantly extend lifespan in banged flies, but markedly extended lifespan in unbanged flies. We have thus developed a functional model for the study of post-TBI elevations of aggression. Further, we conclude that dietary interventions may be a fruitful avenue for further exploration of treatments for TBI- and CTE-related cognitive-behavioral symptoms.

Chronic Traumatic Encephalopathy and Neurodegeneration in Contact Sports and American Football

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease characterized by the presence of abnormally phosphorylated tau protein in the depths of one or more cortical sulci. Controversy over the risk of CTE and neurologic disorders later in life among contact sport athletes has taken hold in the public spotlight, most notably in American football. Players, parents, coaches, and legislators have taken action based on the commonly held notion that contact sports invariably lead to neurodegenerative disorders. However, to fully understand the science behind this assumed association, a critical appraisal of the evidence is warranted. With regards to CTE in sports, the objectives of the current report are to: 1) describe the history of CTE, 2) review current CTE definitions, 3) critically evaluate the empiric data, divided into all contact sports and exclusively American football, and 4) summarize notable themes for future research.

Emerging advances of in vivo detection of chronic traumatic encephalopathy and traumatic brain injury

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disorder that is of epidemic proportions in contact sports athletes and is linked to subconcussive and concussive repetitive head impacts (RHI). Although postmortem analysis is currently the only confirmatory method to diagnose CTE, there has been progress in early detection techniques of fluid biomarkers as well as in advanced neuroimaging techniques. Specifically, promising new methods of diffusion MRI and radionucleotide PET scans could aid in the early detection of CTE.The authors examine early detection methods focusing on various neuroimaging techniques. Advances in structural and diffusion MRI have demonstrated the ability to measure volumetric and white matter abnormalities associated with CTE. Recent studies using radionucleotides such as flortaucipir and 18F-FDDNP have shown binding patterns that are consistent with the four stages of neurofibrillary tangle (NFT) distribution postmortem. Additional research undertakings focusing on fMRI, MR spectroscopy, susceptibility-weighted imaging, and singlephoton emission CT are also discussed as are advanced MRI methods such as diffusiontensor imaging and arterial spin labeled. Neuroimaging is fast becoming a key instrument in early detection and could prove essential for CTE quantification. This review explores a global approach to in vivo early detection.Limited data of in vivo CTE biomarkers with postmortem confirmation are available. While some data exist, they are limited by selection bias. It is unlikely that a single test will be sufficient to properly diagnosis and distinguish CTE from other neurodegenerative diseases such as Alzheimer disease or Frontotemporal Dementia. However, with a combination of fluid biomarkers, neuroimaging, and genetic testing, early detection may become possible.

Assessing the Limitations and Biases in the Current Understanding of Chronic Traumatic Encephalopathy

Chronic traumatic encephalopathy (CTE) is considered to be a progressive neurodegenerative disease caused by mild traumatic brain injury (mTBI). Recently there has been a significant amount of media attention surrounding the commonness of CTE in professional athletes, particularly American football, based on several postmortem case series. However, despite the persuasive claims made by the media about CTE, research on the disease and the effects of mTBI in general remain in its infancy. Commonly cited case series studying CTE are limited by methodological biases, pathological inconsistencies, insufficient clinical data, and a reliance on inherently biased postmortem data. These case series do not allow for the collection of any epidemiological data and are not representative of the general population. The exaggerated assumptions and assertions taken from these studies run the risk of creating a self-fulfilling prophecy for individuals who believe they are at risk and have the potential to negatively influence sports-related policymaking. This review outlines the status and limitations of recent CTE case series and calls for future prospective, longitudinal studies to further characterize the pathological and clinical hallmarks of CTE.

Chronic Traumatic Encephalopathy: A Brief Overview

Chronic Traumatic Encephalopathy (CTE) is a debilitating neurodegenerative disease, which has been increasingly reported in athletes, especially American football players, as well as military veterans in combat settings, commonly as a result of repetitive mild traumatic brain injuries (TBIs). CTE has a unique neuropathological signature comprised of accumulation of phosphorylated tau (p-tau) in sulci and peri-vascular regions, microgliosis, and astrocytosis. As per most recent disease classification, the disease manifests itself in four different stages, characterized by widespread tauopathy. Clinically, CTE has a more subtle presentation, as patients often present with two distinct phenotypes, with one subtype initially presenting with affective changes, and the other subtype with more cognitive impairment. On a genetic basis, there are no clear risk factor genes. Although ApoE4 carriers have been reported to suffer more severe outcome post TBI. As there are no disease modifying regimen for CTE, the newly developed TBI treatments, if administered in a time sensitive manner, can offer a potential viable option. Prevention is another key strategy that needs to be implemented in various sports and military settings. Providing education for safe practice techniques, such as safe tackling and hitting, and providing ready access to full neuropsychiatric assessment by team physician could have measurable benefits. The combination of advanced of research techniques including neuroimaging, as well as increasing public awareness of CTE, offers promising vistas for research advancement.

Video corroboration of player incurred impacts using trunk worn sensors among national ice-hockey team members

PURPOSE

Video corroboration of player incurred impacts (PII) using trunk-worn wearable sensors (WS) among national ice-hockey team members.

METHODS

23 members of the U.S. National (NTDP) U18 team consented to procedures approved by EMU Human Subjects Committee. Bioharness-3 (Zephyr, MD) WS recorded occurrences of PII during games and impacts were generated using Impact Processor (Zephyr, MD). Eight players with the top activity levels each game determined by WS, were observed using video and synchronized with game video collected by NTDP staff. Impacts identified by WS of 6-7.9 g (Z3), 8-9.9 g (Z4) and 10+ g (Z5) were used to corroborate PII. Magnitude and duration of each identified impact were compared by category using MANOVA with Tukey post hoc (α = 0.05; SPSS 22.0, IBM, NY).

RESULTS

Of 419 on-ice impacts, 358 were confirmed true PII (85.5%), 60 as other non-PII (14.3%) and 1 false positive (0.2%). For 358 PII, 17 (4.1%) were 1) Board contact/no check, 74 (17.7%), 2) Board contact/check, 202 (48.2%), 3) Open ice check, 65 (15.5%), 4) Player fall. Of 60 Non-PII, 19 (4.5%) as 5) other form of player to player event, 16 (3.8%) as 6) Hard Stop, 19 (4.5%) as 7) Slapshots and 6 (1.4%) as 8) other identifiable player events. 160 of the 200 Z3 events were PII (80%), 103 of 110 Z4 events (93.6%) and 95 of 109 Z5 events were PII (87.2%). The magnitude of impacts was not different by category, but the duration of category 6 (Hard stop; .058 s) was lower than categories 2, 4 and 7 (.112, .112, .133 s, respectively, p < .05).

CONCLUSION

These data show that using some limited criteria (e.g. impact magnitude and duration), PII can be identified with relatively high accuracy in ice hockey using trunk-worn wearable sensors.

Age of First Exposure to American Football and Behavioral, Cognitive, Psychological, and Physical Outcomes in High School and Collegiate Football Players

BACKGROUND

Although some studies have observed a relationship between age of first exposure (AFE) to American football and long-term outcomes, recent findings in collegiate athletes did not observe a relationship between AFE and more intermediate outcomes at early adulthood. This, however, requires independent replication.

HYPOTHESIS

There will be no association between AFE to football and behavioral, cognitive, emotional/psychological, and physical functioning in high school and collegiate athletes.

STUDY DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Active high school and collegiate football players (N = 1802) underwent a comprehensive preseason evaluation on several clinical outcome measures. Demographic and health variables that significantly differed across AFE groups were identified as potential covariates. General linear models (GLMs) with AFE as the independent variable were performed for each clinical outcome variable. Similar GLMs that included identified covariates, with AFE as the predictor, were subsequently performed for each clinical outcome variable.

RESULTS

After controlling for covariates of age, concussion history, race, and a diagnosis of ADHD, earlier AFE (<12 vs ≥12 years) did not significantly predict poorer performance on any clinical outcome measures (all P > 0.05). A single statistically significant association between AFE group and somatization score was recorded, with AFE <12 years exhibiting lower levels of somatization.

CONCLUSION

In a large cohort of active high school and collegiate football student-athletes, AFE before the age of 12 years was not associated with worse behavioral, cognitive, psychological, and physical (oculomotor functioning and postural stability) outcomes.

CLINICAL RELEVANCE

The current findings suggest that timing of onset of football exposure does not result in poorer functioning in adolescence and young adults and may contribute to resilience through decreased levels of physically related psychological distress.

Low-Field Magnetic Stimulation Restores Cognitive and Motor Functions in the Mouse Model of Repeated Traumatic Brain Injury: Role of Cellular Prion Protein

Traumatic brain injury (TBI)/concussion is a growing epidemic throughout the world. Memory and neurobehavioral dysfunctions are among the sequelae of TBI. Dislodgement of cellular prion protein (PrPc) and disruption of circadian rhythm have been linked to TBI. Low-field magnetic stimulation (LFMS) is a new noninvasive repetitive transcranial magnetic stimulation (rTMS) technique that generates diffused and low-intensity magnetic stimulation to deep cortical and subcortical areas. The role of LFMS on PrPc, proteins related to the circadian rhythm, and behavior alterations in a repeated TBI mouse model were studied in the present study. TBI was induced to the mice (right hemisphere) using weight-drop method, once daily for 3 days. LFMS treatment was given for 20 min once daily for 4 days (immediately after each TBI induction). The results showed that LFMS-treated TBI mice significantly improved cognitive and motor function as evidenced by open field exploration, rotarod, and novel location recognition tasks. In addition, a significant increase in PrPc and decreased glial fibrillary acidic protein levels were observed in cortical and hippocampal regions of LFMS-treated TBI mice brain compared with sham-treated TBI mice, while neuronal nuclei level was significantly increased in cortical region. In LFMS-treated mice, a decrease in proteins related to circadian rhythm were observed, compared with sham-treated TBI mice. The results obtained from the study demonstrated the neuroprotective effect of LFMS, which may be through regulating PrPc and/or proteins related to circadian rhythm. Thus, the present study suggests that LFMS may improve the subject's neurological condition following TBI.

Lateral impacts correlate with falx cerebri displacement and corpus callosum trauma in sports-related concussions

Corpus callosum trauma has long been implicated in mild traumatic brain injury (mTBI), yet the mechanism by which forces penetrate this structure is unknown. We investigated the hypothesis that coronal and horizontal rotations produce motion of the falx cerebri that damages the corpus callosum. We analyzed previously published head kinematics of 115 sports impacts (2 diagnosed mTBI) measured with instrumented mouthguards and used finite element (FE) simulations to correlate falx displacement with corpus callosum deformation. Peak coronal accelerations were larger in impacts with mTBI (8592 rad/s² avg.) than those without (1412 rad/s² avg.). From FE simulations, coronal acceleration was strongly correlated with deep lateral motion of the falx center (r = 0.85), while horizontal acceleration was correlated with deep lateral motion of the falx periphery (r > 0.78). Larger lateral displacement at the falx center and periphery was correlated with higher tract-oriented strains in the corpus callosum body (r = 0.91) and genu/splenium (r > 0.72), respectively. The relationship between the corpus callosum and falx was unique: removing the falx from the FE model halved peak strains in the corpus callosum from 35% to 17%. Consistent with model results, we found indications of corpus callosum trauma in diffusion tensor imaging of the mTBI athletes. For a measured alteration of consciousness, depressed fractional anisotropy and increased mean diffusivity indicated possible damage to the mid-posterior corpus callosum. Our results suggest that the corpus callosum may be sensitive to coronal and horizontal rotations because they drive lateral motion of a relatively stiff membrane, the falx, in the direction of commissural fibers below.

Modifiable risk factors for young onset dementia

PURPOSE OF REVIEW

Although young onset dementia (YOD) causes high levels of burden and distress, factors that contribute to its onset are not well understood. Identifying relevant modifiable risk and protective factors for YOD can inform efforts to prevent or delay onset of symptoms to later in life.

RECENT FINDINGS

Studies of modifiable factors for YOD have increased in frequency in recent years. Poor educational attainment and low socioeconomic status, a history of heavy alcohol use, and poor cardiovascular health may be key targets for YOD prevention or delay. Traumatic brain injury has attracted significant attention but evidence of its importance is limited except in cases occurring secondarily to the injury.

SUMMARY

A growing body of evidence suggests that modifiable risk factors have a role in modulating the age of dementia onset. Clinicians should be aware that many people with YOD will present with complex histories of multifactorial (including modifiable and nonmodifiable) risk exposure. Exploring trajectories of risk and gene-environment interactions is an important future research direction and will inform targeted prevention efforts.

Dangers of Mixed Martial Arts in the Development of Chronic Traumatic Encephalopathy

Chronic traumatic encephalopathy (CTE) was first discovered in professional boxers after they exhibited memory impairments, mood and behavioral changes after years of boxing. However, there is now a growing acceptance that CTE can develop in athletes of other sports due to the repetitive head trauma they receive. We present a case of a middle-aged male who presented with worsening memory, poor concentration, and behavioral changes for a year. On further cognitive testing, it was revealed that he had difficulties with short-term memory and processing speed as well as difficulties in organizing and multitasking. He had been practicing mixed martial arts (MMA) for 10 years, and later was an instructor of the sport. Through a detailed examination of his history, it was discovered that he sustained recurrent minor head concussions due to his line of work. To date, there has been limited large-scale research on head trauma in MMA. There is thus an urgent need for more studies in this area as CTE can be a chronic and debilitating illness with incapacitating neuropsychiatric sequelae. This case highlights the importance of public awareness of the risks of MMA and the dangers it poses to the brain, especially with more young people being attracted to this sport.

The course and prognostic factors of cognitive outcomes after traumatic brain injury: A systematic review and meta-analysis

Despite indications that TBI may be a precursor of cognitive decline and subsequent development of Alzheimer's disease, little is known about the time course of this relationship and the factors involved. This systematic review summarizes the evidence pertinent to this subject matter. All English language studies of longitudinal design, and works cited within them, found in six literature databases, were considered, and their quality assessed. Of 65 articles appraised, 44 studies were selected. Results were organized by timing of assessments, injury severity, and cognitive domains assessed. Differences in the course of cognitive performance were observed across injury severity groups and cognitive domains, with differential proportions of reports of improvement, decline, or no change over time. The evidence for genetic, sex-, age-, and injury-related factors as determinants of cognitive outcome was inconsistent. The non-uniform trajectory of cognitive performance post-TBI supports the notion that this construct is non-homogeneous, and that different factors influence its course. Agreement on a core set of predictors and consideration of psychometric properties of outcome measures is needed.