Research Letter: Sleep Mediates the Association Between Prior Concussion and Depressive Symptoms

OBJECTIVE

To test sleep quality as one mechanistic pathway through which repeated concussion increases risk of depression later in life among former contact sport athletes.

SETTING

Multicenter study enrolled former American collegiate football players from 16 different National Collegiate Athletic Association member institutions.

PARTICIPANTS

Fifty-eight former American collegiate football players approximately 15 years following sport discontinuation.

DESIGN

Participants completed in-person evaluations including comprehensive semistructured interviews with detailed concussion history and sport history, as well as self-reported measures of depression symptom severity (Beck Depression Inventory-II) and sleep quality (Pittsburgh Sleep Quality Index). Years of football participation were included as a covariate. Mediation modeling examined the degree to which sleep quality accounted for the association between repeated concussion and depression symptoms.

RESULTS

Within the mediation model, concussion history significantly predicted sleep quality (B = 1.03; 95% CI, 0.37 to 1.65; P = .002) and sleep quality significantly predicted depressive symptom severity (controlling for the effects of concussion history; B = 0.15; 95% CI, 0.06 to 0.24; P = .001). The association between prior concussion and depressive symptom severity was fully mediated by sleep quality. With inclusion of the indirect effects, concussion history did not predict depressive symptom severity (direct effect: B = 0.14; 95% CI, -0.09 to 0.41; P = .249; indirect effect: 0.15; 95% CI, 0.03 to 0.29; P = .016).

CONCLUSIONS

Current findings raise the possibility that the greater risk of depression reported in those with a history of mTBI/concussion is mediated by sleep quality, a common sequela of mTBI. These findings highlight potential opportunities for prophylactic sleep-related intervention among individuals with multiple prior concussions to mitigate the risk of depression.

Association of Previous Concussion with Hippocampal Volume and Symptoms in Collegiate-Aged Athletes

There is concern that previous concussion and contact-sport exposure may have negative effects on brain structure and function. Accurately quantifying previous concussion is complicated by the fact that multiple definitions exist, with recent definitions allowing for diagnosis based on the presence of symptoms alone (Concussion in Sport Group criteria; CISG) rather than the presence of acute injury characteristics such as alterations in mental status (American Congress of Rehabilitation Medicine criteria; ACRM). The goals of the current work were to determine the effects of previous concussion and contact-sport exposure on gray matter structure and clinical measures in healthy, young-adult athletes and determine the extent to which these associations are influenced by diagnostic criteria used to retrospectively quantify concussions. One-hundred eight collegiate-aged athletes were enrolled; 106 athletes were included in final analyses (age, 21.37 ± 1.69; 33 female). Participants completed a clinical battery of self-report and neurocognitive measures and magnetic resonance imaging to quantify subcortical volumes and cortical thickness. Semistructured interviews were conducted to measure exposure to contact sports and the number of previous concussions based on CISG and ACRM criteria. There was a significant association of concussion-related and psychological symptoms with previous concussions based on ACRM (ps < 0.05), but not CISG, criteria. Hippocampal volume was inversely associated with the number of previous concussions for both criteria (ps < 0.05). Findings provide evidence that previous concussions are associated with smaller hippocampal volumes and greater subjective clinical symptoms in otherwise healthy athletes and highlight the importance of diagnostic criteria used to quantify previous concussion.

Latent Profile Analysis of Neuropsychiatric Symptoms and Cognitive Function of Adults 2 Weeks After Traumatic Brain Injury: Findings From the TRACK-TBI Study

Importance

Heterogeneity across patients with traumatic brain injury (TBI) presents challenges for clinical care and intervention design. Identifying distinct clinical phenotypes of TBI soon after injury may inform patient selection for precision medicine clinical trials.

Objective

To investigate whether distinct neurobehavioral phenotypes can be identified 2 weeks after TBI and to characterize the degree to which early neurobehavioral phenotypes are associated with 6-month outcomes.

Design, Setting, and Participants

This prospective cohort study included patients presenting to 18 US level 1 trauma centers within 24 hours of TBI from 2014 to 2019 as part of the Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) study. Data were analyzed from January 28, 2020, to January 11, 2021.

Exposures

TBI.

Main Outcomes and Measures

Latent profiles (LPs) were derived from common dimensions of neurobehavioral functioning at 2 weeks after injury, assessed through National Institutes of Health TBI Common Data Elements (ie, Brief Symptom Inventory-18, Patient Health Questionnaire-9 Depression checklist, Posttraumatic Stress Disorder Checklist for DSM-5, PROMIS Pain Intensity scale, Insomnia Severity Index, Rey Auditory Verbal Learning Test, Wechsler Adult Intelligence Scale-Fourth Edition Coding and Symbol Search subtests, Trail Making Test, and NIH Toolbox Cognitive Battery Pattern Comparison Processing Speed, Dimensional Change Card Sort, Flanker Inhibitory Control and Attention, and Picture Sequence Memory subtests). Six-month outcomes were the Satisfaction With Life Scale (SWLS), Quality of Life after Brain Injury-Overall Scale (QOLIBRI-OS), Glasgow Outcome Scale-Extended (GOSE), and Rivermead Post-Concussion Symptoms Questionnaire (RPQ).

Results

Among 1757 patients with TBI included, 1184 (67.4%) were men, and the mean (SD) age was 39.9 (17.0) years. LP analysis revealed 4 distinct neurobehavioral phenotypes at 2 weeks after injury: emotionally resilient (419 individuals [23.8%]), cognitively impaired (368 individuals [20.9%]), cognitively resilient (620 individuals [35.3%]), and neuropsychiatrically distressed (with cognitive weaknesses; 350 individuals [19.9%]). Adding LP group to models including demographic characteristics, medical history, Glasgow Coma Scale score, and other injury characteristics was associated with significantly improved estimation of association with 6-month outcome (GOSE R2 increase = 0.09-0.19; SWLS R2 increase = 0.12-0.22; QOLIBRI-OS R2 increase = 0.14-0.32; RPQ R2 = 0.13-0.34).

Conclusions and Relevance

In this cohort study of patients with TBI presenting to US level-1 trauma centers, qualitatively distinct profiles of symptoms and cognitive functioning were identified at 2 weeks after TBI. These distinct phenotypes may help optimize clinical decision-making regarding prognosis, as well as selection and stratification for randomized clinical trials.

Distinct latent profiles based on neurobehavioural, physical and psychosocial functioning of former National Football League (NFL) players: an NFL-LONG Study

OBJECTIVE

To identify subgroups of former National Football League (NFL) players using latent profile analysis (LPA) and examine their associations with total years of participation (TYP) and self-reported lifetime sport-related concussion history (SR-CHx).

METHODS

Former NFL players (N=686) aged 50-70 years, with an average 18.0 TYP (±4.5) completed a questionnaire. SR-CHx distributions included: low (0-3; n=221); intermediate (4-8; n=209) and high (9+; n=256). LPA measures included: Quality of Life in Neurological Disorders Emotional-Behavioral Dyscontrol, Patient Reported Outcomes Measurement Information System Cognitive Function, Emotional Support, Self-Efficacy, Meaning and Purpose, Physical Function, Pain Interference, Participation in Social Roles and Activities, Anxiety, Depression, Fatigue, and Sleep Disturbance. Demographic, medical/psychiatric history, current psychosocial stressors, TYP and SR-CHx were compared across latent profiles (LPs).

RESULTS

A five profile solution emerged: (LP1) global higher functioning (GHF; 26.5%); (LP2) average functioning (10.2%); (LP3) mild somatic (pain and physical functioning) concerns (22.0%); (LP4) somatic and cognitive difficulties with mild anxiety (SCA; 27.5%); LP5) global impaired functioning (GIF; 13.8%). The GIF and SCA groups reported the largest number ofe- medical/psychiatric conditions and higher psychosocial stressor levels. SR-CHx was associated with profile group (χ²(8)=100.38, p<0.001); with a higher proportion of GIF (72.6%) and SCA (43.1%) groups reporting being in the high SR-CHx category, compared with GHF (23.1%), average (31.4%) and somatic (27.8%) groups. TYP was not significantly associated with group (p=0.06), with greater TYP reported by the GHF group.

CONCLUSIONS

Five distinct profiles of self-reported functioning were identified among former NFL players. Several comorbid factors (ie, medical/psychiatric diagnoses and psychosocial stressors) and SR-CHx were associated with greater neurobehavioural and psychosocial dysfunction.

Association of Head Impact Exposure with White Matter Macrostructure and Microstructure Metrics

Prior studies have reported white matter abnormalities associated with a history of cumulative concussion and/or repetitive head impacts (RHI) in contact sport athletes. Growing evidence suggests these abnormalities may begin as more subtle changes earlier in life in active younger athletes. We investigated the relationship between prior concussion and contact sport exposure with multi-modal white matter microstructure and macrostructure using magnetic resonance imaging. High school and collegiate athletes (n = 121) completed up to four evaluations involving neuroimaging. Linear mixed-effects models examined associations of years of contact sport exposure (i.e., RHI proxy) and prior concussion across multiple metrics of white matter, including total white matter volume, diffusion tensor imaging (DTI) metrics, diffusion kurtosis imaging (DKI) metrics, and quantitative susceptibility mapping (QSM). A significant inverse association between cumulative years of contact sport exposure and QSM was observed, F(1, 237.77) = 4.67, p = 0.032. Cumulative contact sport exposure was also associated with decreased radial diffusivity, F(1, 114.56) = 5.81, p = 0.018, as well as elevated fractional anisotropy, F(1, 115.32) = 5.40, p = 0.022, and radial kurtosis, F(1, 113.45) = 4.03, p = 0.047. In contrast, macroscopic white matter volume was not significantly associated with cumulative contact sport exposure (p > 0.05). Concussion history was not significantly associated with QSM, DTI, DKI, or white matter volume (all, p > 0.05). Cumulative contact sport exposure is associated with subtle differences in white matter microstructure, but not gross white matter macrostructure, in young active athletes. Longitudinal follow-up is required to assess the progression of these findings to determine their contribution to potential adverse effects later in life.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Positive association between serum quinolinic acid and functional connectivity following concussion

The molecular mechanisms underlying the diverse psychiatric and neuropathological sequalae documented in subsets of athletes with concussion have not been identified. We have previously reported elevated quinolinic acid (QuinA), a neurotoxic kynurenine pathway metabolite, acutely following concussion in football players with prior concussion. Similarly, work from our group and others has shown that increased functional connectivity strength, assessed using resting state fMRI, occurs following concussion and is associated with worse concussion-related symptoms and outcome. Moreover, other work has shown that repetitive concussion may have cumulative effects on functional connectivity and is a risk factor for adverse outcomes. Understanding the molecular mechanisms underlying these cumulative effects may ultimately be important for therapeutic interventions or the development of prognostic biomarkers. Thus, in this work, we tested the hypothesis that the relationship between QuinA in serum and functional connectivity following concussion would depend on the presence of a prior concussion. Concussed football players with prior concussion (N = 21) and without prior concussion (N = 16) completed a MRI session and provided a blood sample at approximately 1 days, 8 days, 15 days, and 45 days post-injury. Matched, uninjured football players with (N = 18) and without prior concussion (N = 24) completed similar visits. The association between QuinA and global connectivity strength differed based on group (F(3, 127) = 3.46, p = 0.019); post-hoc analyses showed a positive association between QuinA and connectivity strength in concussed athletes with prior concussion (B = 16.05, SE = 5.06, p = 0.002, 95%CI[6.06, 26.03]), but no relationship in concussed athletes without prior concussion or controls. Region-specific analyses showed that this association was strongest in bilateral orbitofrontal cortices, insulae, and basal ganglia. Finally, exploratory analyses found elevated global connectivity strength in concussed athletes with prior concussion who reported depressive symptoms at the 1-day visit compared to those who did not report depressive symptoms (t(15) = 2.37, mean difference = 13.50, SE = 5.69, p = 0.032, 95%CI[1.36, 25.63], Cohen's d = 1.15.). The results highlight a potential role of kynurenine pathway (KP) metabolites in altered functional connectivity following concussion and raise the possibility that repeated concussion has a "priming" effect on KP metabolism.

Systemic inflammation moderates the association of prior concussion with hippocampal volume and episodic memory in high school and collegiate athletes

BACKGROUND

There is a need to determine why prior concussion has been associated with adverse outcomes in some retired and active athletes. We examined whether serum inflammatory markers moderate the associations of prior concussion with hippocampal volumes and neurobehavioral functioning in active high school and collegiate athletes.

METHODS

Athletes (N = 201) completed pre-season clinical testing and serum collection (C-reactive protein [CRP]; Interleukin-6 [IL]-6; IL-1 receptor antagonist [RA]) and in-season neuroimaging. Linear mixed-effects models examined associations of prior concussion with inflammatory markers, self-reported symptoms, neurocognitive function, and hippocampal volumes. Models examined whether inflammatory markers moderated associations of concussion history and hippocampal volume and/or clinical measures.

RESULTS

Concussion history was significantly associated with higher symptom severity, p = 0.012, but not hippocampal volume or inflammatory markers (ps > 0.05). A significant interaction of prior concussion and CRP was observed for hippocampal volume, p = 0.006. Follow-up analyses showed that at high levels of CRP, athletes with two or more prior concussions had smaller hippocampal volume compared to athletes without prior concussion, p = 0.008. There was a significant interaction between prior concussion and levels of IL-1RA on memory scores, p = 0.044, i.e., at low levels of IL-1RA, athletes with two or more concussions had worse memory performance than those without prior concussion (p = 0.014).

CONCLUSION

Findings suggest that certain markers of systemic inflammation moderate the association between prior concussion and hippocampal volume and episodic memory performance. Current findings highlight potential markers for predicting at-risk individuals and identify therapeutic targets for mitigating the long-term adverse consequences of cumulative concussion.

Prospective study of the association between sport-related concussion and brain morphometry (3T-MRI) in collegiate athletes: study from the NCAA-DoD CARE Consortium

OBJECTIVES

To determine the acute and early long-term associations of sport-related concussion (SRC) and subcortical and cortical structures in collegiate contact sport athletes.

METHODS

Athletes with a recent SRC (n=99) and matched contact (n=91) and non-contact sport controls (n=95) completed up to four neuroimaging sessions from 24 to 48 hours to 6 months postinjury. Subcortical volumes (amygdala, hippocampus, thalamus and dorsal striatum) and vertex-wise measurements of cortical thickness/volume were computed using FreeSurfer. Linear mixed-effects models examined the acute and longitudinal associations between concussion and structural metrics, controlling for intracranial volume (or mean thickness) and demographic variables (including prior concussions and sport exposure).

RESULTS

There were significant group-dependent changes in amygdala volumes across visits (p=0.041); this effect was driven by a trend for increased amygdala volume at 6 months relative to subacute visits in contact controls, with no differences in athletes with SRC. No differences were observed in any cortical metric (ie, thickness or volume) for primary or secondary analyses.

CONCLUSION

A single SRC had minimal associations with grey matter structure across a 6-month time frame.

Bifactor Model of the Sport Concussion Assessment Tool Symptom Checklist: Replication and Invariance Across Time in the CARE Consortium Sample

BACKGROUND

Identifying separate dimensions of concussion symptoms may inform a precision medicine approach to treatment. It was previously reported that a bifactor model identified distinct acute postconcussion symptom dimensions.

PURPOSE

To replicate previous findings of a bifactor structure of concussion symptoms in the Concussion Assessment Research and Education (CARE) Consortium sample, examine measurement invariance from pre- to postinjury, and evaluate whether factors are associated with other clinical and biomarker measures.

STUDY DESIGN

Cohort study (Diagnosis); Level of evidence, 2.

METHODS

Collegiate athletes were prospectively evaluated using the Sport Concussion Assessment Tool-3 (SCAT-3) during preseason (N = 31,557); 2789 were followed at <6 hours and 24 to 48 hours after concussion. Item-level SCAT-3 ratings were analyzed using exploratory and confirmatory factor analyses. Bifactor and higher-order models were compared for their fit and interpretability. Measurement invariance tested the stability of the identified factor structure across time. The association between factors and criterion measures (clinical and blood-based markers of concussion severity, symptom duration) was evaluated.

RESULTS

The optimal structure for each time point was a 7-factor bifactor model: a General factor, on which all items loaded, and 6 specific factors-Vestibulo-ocular, Headache, Sensory, Fatigue, Cognitive, and Emotional. The model manifested strict invariance across the 2 postinjury time points but only configural invariance from baseline to postinjury. From <6 to 24-48 hours, some dimensions increased in severity (Sensory, Fatigue, Emotional), while others decreased (General, Headache, Vestibulo-ocular). The factors correlated with differing clinical and biomarker criterion measures and showed differing patterns of association with symptom duration at different time points.

CONCLUSION

Bifactor modeling supported the predominant unidimensionality of concussion symptoms while revealing multidimensional properties, including a large dominant General factor and 6 independent factors: Headache, Vestibulo-ocular, Sensory, Cognitive, Fatigue, and Emotional. Unlike the widely used SCAT-3 symptom severity score, which declines gradually after injury, the bifactor model revealed separable symptom dimensions that have distinct trajectories in the acute postinjury period and different patterns of association with other markers of injury severity and outcome.

CLINICAL RELEVANCE

The SCAT-3 total score remains a valuable, robust index of overall concussion symptom severity, and the specific factors identified may inform management strategies. Because some symptom dimensions continue to worsen in the first 24 to 48 hours after injury (ie, Sensory, Fatigue, Emotional), routine follow-up in this time frame may be valuable to ensure that symptoms are managed effectively.

2020 COVID-19 American Academy of Clinical Neuropsychology (AACN) Student Affairs Committee survey of neuropsychology trainees

Objective: To conduct an online survey in order to understand neuropsychology trainees' perspectives during the COVID-19 pandemic and identify pertinent concerns, training gaps, and recommendations.Method: A total of 874 neuropsychology trainees (81% female) completed the 69-item survey. Of the included trainees, 48% were doctoral students, 17% were interns, and 35% were postdoctoral residents (50% of resident respondents were in their first year).Results: The majority of neuropsychology trainees reported some impact of the pandemic on their professional and/or personal life. Overall, the impact did not differ by training level, geographic location, or demographic factors. Trainees' primary professional concerns included uncertainty about the impact of the pandemic on their professional future, loss of clinical hours, and desire for increased and ongoing communication from their leadership. A notable percentage of trainees reported increased personal mental health symptoms (i.e. anxiety/depression; 74%/54%), as well as a number of other personal stressors. Despite the transition to telehealth (mostly interviews/feedback sessions), few trainees have prior training or experience in providing neuropsychological services via phone or video platform. A limited proportion of trainees (approximately 10%) were still seeing patients face-to-face for neuropsychological evaluations during the COVID-19 pandemic as of 14 April 2020.Conclusions: The COVID-19 pandemic is impacting neuropsychological training and the well-being of trainees. This survey highlights the importance of communication with trainees during uncertain times. Based on the survey results, recommendations were developed to assist neuropsychology organizations in developing initiatives to support trainees during the current pandemic and in the future.

Cumulative Effects of Prior Concussion and Primary Sport Participation on Brain Morphometry in Collegiate Athletes: A Study From the NCAA-DoD CARE Consortium

Prior studies have reported long-term differences in brain structure (brain morphometry) as being associated with cumulative concussion and contact sport participation. There is emerging evidence to suggest that similar effects of prior concussion and contact sport participation on brain morphometry may be present in younger cohorts of active athletes. We investigated the relationship between prior concussion and primary sport participation with subcortical and cortical structures in active collegiate contact sport and non-contact sport athletes. Contact sport athletes (CS; N = 190) and matched non-contact sport athletes (NCS; N = 95) completed baseline clinical testing and participated in up to four serial neuroimaging sessions across a 6-months period. Subcortical and cortical structural metrics were derived using FreeSurfer. Linear mixed-effects (LME) models examined the effects of years of primary sport participation and prior concussion (0, 1+) on brain structure and baseline clinical variables. Athletes with prior concussion across both groups reported significantly more baseline concussion and psychological symptoms (all ps < 0.05). The relationship between years of primary sport participation and thalamic volume differed between CS and NCS (p = 0.015), driven by a significant inverse association between primary years of participation and thalamic volume in CS (p = 0.007). Additional analyses limited to CS alone showed that the relationship between years of primary sport participation and dorsal striatal volume was moderated by concussion history (p = 0.042). Finally, CS with prior concussion had larger hippocampal volumes than CS without prior concussion (p = 0.015). Years of contact sport exposure and prior concussion(s) are associated with differences in subcortical volumes in young-adult, active collegiate athletes, consistent with prior literature in retired, primarily symptomatic contact sport athletes. Longitudinal follow-up studies in these athletes are needed to determine clinical significance of current findings.

The Neuropathological and Clinical Diagnostic Criteria of Chronic Traumatic Encephalopathy: A Critical Examination in Relation to Other Neurodegenerative Diseases

This work critically reviews chronic traumatic encephalopathy (CTE), with a specific focus on the single criterion necessary and sufficient for diagnosis. Herein, CTE is compared to other well-established neurodegenerative entities including Alzheimer's disease and dementia with Lewy bodies. Each neurodegenerative disorder is reviewed in five pertinent areas: 1) historical perspective, 2) guideline formation process, 3) clinical diagnostic criteria, 4) pathological diagnostic criteria, and 5) validation of previously described diagnostic criteria (e.g., sensitivity and specificity). These comparisons indicate that CTE is a disease in the earliest stages of formation and has yet to undergo rigorous development and refinement similar to other neurodegenerative diseases. Suggested future revisions to the diagnostic criterion of CTE include establishing a lower threshold for accumulation of pathology, as well as accounting for the presence of concomitant neuropathology and comorbid neurodegenerative disorders. Currently, while initial efforts have been attempted, agreed upon antemortem clinical criteria do not exist. As has been the scientific standard with similar neurodegenerative disorders, antemortem diagnostic guidelines should first be refined through subcommittees of neuroscientists from diverse institutional backgrounds with a subclassification of levels of diagnostic certainty (possible, probably, and definite). Validation studies should then assess the predictive value and accuracy of proposed antemortem diagnostic criteria in relation to potential pathological criteria.

Investigating the Range of Symptom Endorsement at Initiation of a Graduated Return-to-Play Protocol After Concussion and Duration of the Protocol: A Study From the National Collegiate Athletic Association-Department of Defense Concussion, Assessment, Research, and Education (CARE) Consortium

BACKGROUND

Organizations recommend that athletes should be asymptomatic or symptom-limited before initiating a graduated return-to-play (GRTP) protocol after sports-related concussion, although asymptomatic or symptom-limited is not well-defined.

HYPOTHESES

(1) There will be a range (ie, beyond zero as indicator of "symptom-free") in symptom severity endorsement when athletes are deemed ready to initiate a GRTP protocol. (2) Baseline symptom severity scores and demographic/preinjury medical history factors influence symptom severity scores at the commencement of the GRTP protocol. (3) Greater symptom severity scores at GRTP protocol initiation will result in longer protocol duration. (4) Symptom severity scores will not differ between those who did and did not sustain a repeat injury within 90 days of their initial injury.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Across 30 universities, athletes (N = 1531) completed assessments at baseline and before beginning the GRTP protocol, as determined by local medical staff. Symptom severity scores were recorded with the symptom checklist of the Sport Concussion Assessment Tool-3rd Edition. Nonparametric comparisons were used to examine the effect of medical, demographic, and injury factors on symptom endorsement at GRTP protocol initiation, as well as differences in symptom severity scores between those who did and did not sustain a repeat injury within 90 days. A Cox regression was used to examine the association between symptom severity scores at GRTP protocol initiation and protocol duration.

RESULTS

Symptom severity scores at the time when the GRTP protocol was initiated were as follows: 0 to 5 (n = 1378; 90.0%), 6 to 10 (n = 76; 5.0%), 11 to 20 (n = 42; 3.0%), and ≥21 (n = 35; 2.0%). Demographic (sex and age), medical (psychiatric disorders, attention-deficit/hyperactivity disorder, learning disorder), and other factors (baseline symptom endorsement and sleep) were significantly associated with higher symptom severity scores at the GRTP initiation (P < .05). The 4 GRTP initiation time point symptom severity score groups did not significantly differ in total time to unrestricted RTP, χ²(3) = 1.4; P = .73. When days until the initiation of the GRTP protocol was included as a covariate, symptom severity scores between 11 and 20 (P = .02; hazard ratio = 1.44; 95% CI, 1.06-1.96) and ≥21 (P < .001; hazard ratio = 1.88; 95% CI, 1.34-2.63) were significantly associated with a longer GRTP protocol duration as compared with symptom severity scores between 0 and 5. Symptom severity scores at GRTP initiation did not significantly differ between those who sustained a repeat injury within 90 days and those who did not (U = 29,893.5; P = .75).

CONCLUSION

A range of symptom severity endorsement was observed at GRTP protocol initiation, with higher endorsement among those with higher baseline symptom endorsement and select demographic and medical history factors. Findings suggest that initiation of a GRTP protocol before an absolute absence of all symptoms is not associated with longer progression of the GRTP protocol, although symptom severity scores >10 were associated with longer duration of a GRTP protocol. Results can be utilized to guide clinicians toward optimal GRTP initiation (ie, balancing active recovery with avoidance of premature return to activity).

Chronic traumatic encephalopathy research viewed in the public domain: What makes headlines?

Objective: To determine chronic traumatic encephalopathy (CTE)-related publication characteristics associated with higher Altmetric scores.Methods: A systematic review of the CTE literature was conducted using PubMed. Publications were coded for: journal impact factor (JIF); publication type (primary versus non-primary data collection); discussion of American football; contact sport-CTE association conclusion (yes versus no/neutral); and Altmetric score. Multivariable ordinal logistic regression identified predictors of higher Altmetric scores.Results: Most of the 270 CTE-related publications did not include primary data collection (60%). The median Altmetric score was 12 (range = 0-3745). Higher Altmetric scores were associated with primary data collection [Odds ratio (OR)_Adjusted = 2.29; 95% confidence interval (CI) = 1.35-3.89] and discussing American football (OR_Adjusted = 2.11; 95%CI = 1.24-3.59). Among publications concluding contact sport-CTE associations, higher Altmetric scores were associated with higher JIF (3-point-JIF-increase OR_Adjusted = 2.11; 95%CI = 1.24-3.59); however, the association of higher Altmetric scores with higher JIF was not found among neutral publications or those concluding no contact sport-CTE associations (3-point-JIF-increase OR_Adjusted = 1.07; 95%CI = 0.94-1.22).Conclusions: Most CTE-related publications (60%) did not involve primary data collection. Publication characteristics such as higher JIF and concluding contact sport-CTE associations were associated with higher Altmetric scores. It is important for the academic community to consider strategies to counter publication and promotion bias in the presentation of CTE literature.

The Association Between Persistent White-Matter Abnormalities and Repeat Injury After Sport-Related Concussion

Objective: A recent systematic review determined that the physiological effects of concussion may persist beyond clinical recovery. Preclinical models suggest that ongoing physiological effects are accompanied by increased cerebral vulnerability that is associated with risk for subsequent, more severe injury. This study examined the association between signal alterations on diffusion tensor imaging following clinical recovery of sport-related concussion in athletes with and without a subsequent second concussion. Methods: Average mean diffusivity (MD) was calculated in a region of interest (ROI) in which concussed athletes (n = 82) showed significantly elevated MD acutely after injury (<48 h), at an asymptomatic time point, 7 days post-return to play (RTP), and 6 months relative to controls (n = 69). The relationship between MD in the identified ROI and likelihood of sustaining a subsequent concussion over a 1-year period was examined with a binary logistic regression (re-injured, yes/no). Results: Eleven of 82 concussed athletes (13.4%) sustained a second concussion within 12 months of initial injury. Mean MD at 7 days post-RTP was significantly higher in those athletes who went on to sustain a repeat concussion within 1 year of initial injury than those who did not (p = 0.048; d = 0.75). In this underpowered sample, the relationship between MD at 7 days post-RTP and likelihood of sustaining a secondary injury approached significance [χ2 (1) = 4.17, p = 0.057; B = 0.03, SE = 0.017; OR = 1.03, CI = 0.99, 1.07]. Conclusions: These preliminary findings raise the hypothesis that persistent signal abnormalities in diffusion imaging metrics at RTP following concussion may be predictive of a repeat concussion. This may reflect a window of cerebral vulnerability or increased susceptibility following concussion, though understanding the clinical significance of these findings requires further study.

Functional Status Examination Yields Higher Measurement Precision of Functional Limitations after Traumatic Injury than the Glasgow Outcome Scale-Extended: A Preliminary Study

The Glasgow Outcome Scale-Extended (GOSE) is one of the most widely used measures of functional limitations after traumatic brain injury (TBI), and is the primary outcome measure used in clinical trials of acute TBI treatment. However, the GOSE appears insensitive to the full spectrum of TBI-related functional limitations, which may limit its potential to capture treatment effects or correlate with other variables that impact outcome. The Functional Status Examination (FSE) was designed to improve on the assessment of injury-related functional limitations using a standardized assessment and wider possible score range. The aim of this pilot study was to employ item response theory (IRT) to test the hypothesis that the FSE yields more precise estimation of functional outcome than the GOSE. Traumatically injured patients (n = 100, 77 TBI, 23 orthopedic injuries) were interviewed at 3 months post-injury using both the GOSE and FSE structured interviews. IRT was used to quantify and compare the tests' information functions, which reflect the degree to which each instrument precisely measures functional limitations across the severity spectrum. Findings were consistent with predictions: the FSE yielded stronger measurement of functional limitations (i.e., higher test information) across a wider range of severity than the GOSE, whether scoring the GOSE from all interview items or using the traditional GOSE overall score. Although the FSE appears to be a promising alternative measure to the GOSE, further research is needed to cross-validate these findings in a larger sample and understand how to best deploy it in clinical and translational research.

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.

White Matter Abnormalities on Diffusion Tensor Imaging Following Recovery from Sport-Related Concussion and Risk of Subsequent Re-injury

Purpose

A recent systematic review determined that the physiological effects of concussion may persist beyond clinical recovery. Preclinical models suggest that these physiological effects are accompanied by a window of cerebral vulnerability that is associated with risk for subsequent, more severe injury. This study examined the association between persistent diffusion tensor imaging signal following clinical recovery of sport-related concussion and risk of re-injury.

Methods

Average mean diffusivity (MD) was obtained in a region-of-interest (ROI) in which concussed athletes showed significantly elevated MD acutely after injury (<48 hours), at an asymptomatic timepoint, 7-days post-return to play, and 6 months post-injury relative to controls. The relationship between MD in the identified ROI and risk of sustaining a subsequent concussion over a 1-year period was examined with a binary logistic regression (re-injured, yes/no).

Results

Eleven of 83 concussed athletes suffered a second concussion within a 1-year period. The relationship between MD at 7-days post return to play and risk of sustaining a secondary injury within 1-year showed a non-significant trend (X2(1)=4.17, p=.057, B=0.03, SE=0.017; Nagelkerke R2=0.16). Mean differences in MD between the repeat injury and non-reinjured group at 7-days post return to play produced a large effect, d=.75. MD in the a priori ROI at the other recovery time points did not predict elevated risk of re-injury.

Conclusion

These preliminary findings suggest that a large effect size was present in the relationship between persistent diffusion signal abnormalities and risk for subsequent re-injury. This provides support for a window of cerebral vulnerability following concussion, though further examination is needed.

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.

The Relationship Between Prior Concussions and Depression Is Modified by Somatic Symptomatology in Retired NFL Athletes

A positive relationship between sport-related concussion (SRC) history and depressive symptoms in retired National Football League (NFL) athletes has been observed, with self-rated physical functioning identified as a confounding factor. The authors examined the influence of somatic symptom endorsement on the relationship between SRC history and self-reported depressive symptom severity in retired NFL athletes. Forty-three former NFL athletes completed self-report inventories of depression (with the Beck Depression Inventory II) and somatic symptoms (with the adjusted Patient Health Questionnaire-15). A moderation analysis examined the influence of somatic symptoms on the relationship between SRC history and depressive symptom severity. SRC history and somatic symptoms accounted for a significant amount of depressive symptomology. SRC history was not significantly associated with depressive symptom severity at low levels of somatic symptoms but was significant at the mean and high levels. The effect of somatic symptoms on depressive symptoms was nearly twice that of SRC history. The relationship between SRC and depression is complex, and treatment of depression in retired athletes should address comorbid somatic symptoms.

Imaging findings after acute sport-related concussion in American football players: A systematic review

Sport-related concussion (SRC) has emerged as a major public health problem. The results of brain imaging studies following SRC have raised questions about long-term neurologic health, but the clinical implications of these findings remain unknown. A systematic review of brain imaging findings after SRC was performed utilizing the following inclusion criteria: football players, brain imaging within 6 months of SRC, and sample size >5. Studies were assessed for: 1) methodology, 2) imaging outcomes, and 3) number of positive statistical comparisons. Imaging was classified as immediate (≤1 week post-injury) or subacute (>1 week to 6 months post-injury). Eleven studies met inclusion criteria. Eight of the 11 studies conducted a total of 809 comparisons of brain function, of which 149 (18%) were statistically significant. Nine of the 11 studies (82%) reported positive immediate findings, but were more likely to be subject to recall bias (86% vs. 0%) and to lack baseline advanced brain imaging (78% vs. 50%) than negative studies. Only 3 of 9 studies that reported subacute findings (33%) reported positive results, and these positive studies were also more likely to be subject to recall bias (100% vs. 40%) and to lack baseline advanced brain imaging (100% vs. 67%) than negative studies. The results of the study demonstrate the transitory nature of positive imaging findings and methodological limitations that complicate study interpretation. Further research is required to correlate imaging findings with clinical outcomes.

Prognostic Factors in Pediatric Sport-Related Concussion

PURPOSE OF REVIEW

Sport-related concussion (SRC) and mild traumatic brain injury (mTBI) have been thrust into the national spotlight, with youth athletes bearing the burden of this public health problem. The current review aims to provide a practical summary of pediatric SRC, including key terminology, return to play/school, and risk factors for post-concussion syndrome (PCS).

RECENT FINDINGS

While the majority of youth athletes recover within 2 to 4 weeks, approximately 10% of athletes experience a protracted recovery with symptoms lasting months, impacting social, scholastic, and sporting activities. In the pediatric population, the strongest predictors of PCS are initial symptom burden and prior concussion, with mixed results behind the factors of gender, headaches, and learning disability. The role of psychiatric, family history, sports, and socioeconomic factors remain in their infancy.

The role of family and personal psychiatric history in postconcussion syndrome following sport-related concussion: a story of compounding risk

OBJECTIVE Sport-related concussion (SRC) has become a major public health concern. Prolonged recovery after SRC, named postconcussion syndrome (PCS), has been associated with several biopsychosocial factors, yet the role of both family and personal psychiatric histories requires investigation. In a cohort of concussed high school athletes, the authors examined the role(s) of family and personal psychiatric histories in the risk of developing PCS. METHODS A retrospective cohort study of 154 high school athletes with complete documentation of postconcussion symptom resolution or persistence at 6 weeks was conducted. PCS was defined as 3 or more symptoms present 6 weeks after SRC. Three groups were defined: 1) positive family psychiatric history and personal psychiatric history (FPH/PPH), 2) positive FPH only, and 3) negative family and personal psychiatric histories (controls). Three bivariate regression analyses were conducted: FPH/PPH to controls, FPH only to controls, and FPH/PPH to FPH. Post hoc bivariate regression analyses examined specific FPH pathologies and PCS. RESULTS Athletes with FPH/PPH compared with controls had an increased risk of PCS (χ² = 8.90, p = 0.018; OR 5.06, 95% CI 1.71-14.99). Athletes with FPH only compared with controls also had an increased risk of PCS (χ² = 6.04, p = 0.03; OR 2.52, 95% CI 1.20-5.30). Comparing athletes with FPH/PPH to athletes with FPH only, no added PCS risk was noted (χ² = 1.64, p = 0.247; OR 2.01, 95% CI 0.68-5.94). Among various FPH diagnoses, anxiety (χ² = 7.48, p = 0.021; OR 2.99, 95% CI 1.36-6.49) and bipolar disorder (χ² = 5.13, p = 0.036; OR 2.74, 95% CI 1.14-6.67) were significantly associated with the presence of PCS. CONCLUSIONS Concussed high school athletes with FPH/PPH were greater than 5 times more likely to develop PCS than controls. Athletes with only FPH were over 2.5 times more likely to develop PCS than controls. Those with an FPH of anxiety or bipolar disorder are specifically at increased risk of PCS. These results suggest that not only are athletes with FPH/PPH at risk for slower recovery after SRC, but those with an FPH only-especially anxiety or bipolar disorder-may also be at risk. Overall, this study supports taking a detailed FPH and PPH in the management of SRC.

Improving treatment motivation in individuals with psychosis: Predictors of response to motivational enhancement

We sought to evaluate the influence of demographic, symptom, functional and cognitive factors on task-specific motivation, as well as improvement in task-specific motivation that occurs in response to motivational interviewing. In the absence of any intervention, better task-specific motivation was associated with higher perceived competence and lower symptomatology. Post-motivational enhancement improvement in motivation was predicted by fewer hospitalizations and better cognitive insight, with baseline symptomatology no longer predictive. Findings suggest motivational enhancement is likely to benefit individuals with diverse clinical presentations, though may be particularly well suited to those with lesser disease severity and better cognitive insight.

Initial symptom presentation after high school football-related concussion varies by time point in a season: an initial investigation

Background

Schedule-based and in-season factors (e.g., competition type) have been shown to be associated with symptom reporting patterns and injury severity in sport-related concussion (SRC). To determine if acute neurocognitive and symptom presentation following SRC differ by time point within a high school football season.

Methods

Multicenter ambispective cohort of high school football players who sustained a SRC (N = 2594). Timing (early, mid, and late season) of SRC was based on median dates for the start of the pre-season, regular season, and playoffs of each states’ football schedules. Analysis of covariance (ANCOVA) investigated differences across season period groups for: (1) neurocognitive test scores, (2) total symptom scores (TSS), and (3) individual symptom increases from baseline within 1-week post-injury.

Results

Significant group differences were observed in TSS, F(2, 2589) = 15.40, p <  0.001, η_p² = 0.01, and individual symptom increases from baseline, F(2, 2591) = 16.40, p <  0.001, η_p² = 0.01. Significant increases were seen from baseline to both midseason and late season in both TSS, χ² = 24.40, p <  0.001, Φ = 0.10 and individual symptoms, χ² = 10.32, p = 0.006, Φ = 0.10. Post hoc tests indicated a linear trend, with late-season injured athletes reporting approximately twice the TSS (13.10 vs. 6.77) and new symptoms (5.70 vs. 2.68) as those with early-season injuries.

Conclusion

In a cohort of American high school football student-athletes, those suffering SRC in the late-season time period had increased acute symptom burden. SRC sustained later in-season may require more conservative management.

Team versus individual sport participation as a modifying factor in the development of post-concussion syndrome after first concussion: A pilot study

Identification of modifying factors that influence the development of post-concussion syndrome (PCS) following sport-related concussion (SRC) has drawn considerable interest. In this pilot study, we investigate the effect of team vs. individual sport participation on the development of PCS in a sample of 136 high school and college student-athletes. Controlling for several confounding variables, we employed a binary logistic regression and chi-squared test. Results of this pilot study indicate that participation in team versus individual sport is not a significant factor in the development of PCS. The identification of other forms of protective mechanisms is discussed.

Comparison of Neurocognitive Performance in Contact and Noncontact Nonconcussed High School Athletes Across a Two-Year Interval

Investigating short-term effects of subconcussive impacts on neurocognitive functioning, we employed a repeated measures multivariate model and regression-based measure to examine neurocognitive changes in 771 contact and noncontact high school athletes over a two-year period. Results reveal significant changes in Visual Motor Speed for both groups over a two-year period, with small effect sizes. According to regression-based measures, differences in contact sport athletes' expected Time 2 performances were significant for Visual Motor Speed, also with minimal effects. Results do not conclusively implicate subconcussive hits as the offending factor in differences observed, with gender and sport-type possibly contributing to the small effects.

The influence of validity criteria on Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) test-retest reliability among high school athletes

OBJECTIVE

Research findings to date on the stability of Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) Composite scores have been inconsistent, requiring further investigation. The use of test validity criteria across these studies also has been inconsistent. Using multiple measures of stability, we examined test-retest reliability of repeated ImPACT baseline assessments in high school athletes across various validity criteria reported in previous studies.

METHOD

A total of 1146 high school athletes completed baseline cognitive testing using the online ImPACT test battery at two time periods of approximately two-year intervals. No participant sustained a concussion between assessments. Five forms of validity criteria used in previous test-retest studies were applied to the data, and differences in reliability were compared.

RESULTS

Intraclass correlation coefficients (ICCs) ranged in composite scores from .47 (95% confidence interval, CI [.38, .54]) to .83 (95% CI [.81, .85]) and showed little change across a two-year interval for all five sets of validity criteria. Regression based methods (RBMs) examining the test-retest stability demonstrated a lack of significant change in composite scores across the two-year interval for all forms of validity criteria, with no cases falling outside the expected range of 90% confidence intervals.

CONCLUSION

The application of more stringent validity criteria does not alter test-retest reliability, nor does it account for some of the variation observed across previously performed studies. As such, use of the ImPACT manual validity criteria should be utilized in the determination of test validity and in the individualized approach to concussion management. Potential future efforts to improve test-retest reliability are discussed.

Long-term Stability and Reliability of Baseline Cognitive Assessments in High School Athletes Using ImPACT at 1-, 2-, and 3-year Test-Retest Intervals

OBJECTIVE

The ImPACT (Immediate Post-Concussion Assessment and Cognitive Testing) neurocognitive testing battery is a widely used tool used for the assessment and management of sports-related concussion. Research on the stability of ImPACT in high school athletes at a 1- and 2-year intervals have been inconsistent, requiring further investigation. We documented 1-, 2-, and 3-year test-retest reliability of repeated ImPACT baseline assessments in a sample of high school athletes, using multiple statistical methods for examining stability.

METHODS

A total of 1,510 high school athletes completed baseline cognitive testing using online ImPACT test battery at three time periods of approximately 1- (N = 250), 2- (N = 1146), and 3-year (N = 114) intervals. No participant sustained a concussion between assessments.

RESULTS

Intraclass correlation coefficients (ICCs) ranged in composite scores from 0.36 to 0.90 and showed little change as intervals between assessments increased. Reliable change indices and regression-based measures (RBMs) examining the test-retest stability demonstrated a lack of significant change in composite scores across the various time intervals, with very few cases (0%-6%) falling outside of 95% confidence intervals.

CONCLUSION

The results suggest ImPACT composites scores remain considerably stability across 1-, 2-, and 3-year test-retest intervals in high school athletes, when considering both ICCs and RBM. Annually ascertaining baseline scores continues to be optimal for ensuring accurate and individualized management of injury for concussed athletes. For instances in which more recent baselines are not available (1-2 years), clinicians should seek to utilize more conservative range estimates in determining the presence of clinically meaningful change in cognitive performance.

Control of Meiotic Drive of B Chromosomes in the Mealybug, Pseudococcus affinis (obscurus)

Isofemale lines of Pseudococcus affinis (Maskell) differ in their ability to maintain B chromosomes (Bs) due to the presence of genotypes that affect the rate of transmission (k) of the Bs. The nature of these genotypes was analyzed by comparing ks of males carrying the same B and the same paternal genome (which is heterochromatic), but differing in their maternal genome. In males from line L-60, which maintained the B at a frequency of over 4.0 Bs per individual, the mean k varied between 0.7 and 0.95 in different experiments. Over the same period, the mean k of males with a maternal genome from one of two lines in which the B was rapidly lost (L-119), increased from 0.5 to 0.9, and that of the other line (L-230) decreased gradually from 0.6 to less than 0.1. The ks appear not to be correlated with the geographical or parental origin of the B. The observed changes in k are attributed at least in part to changes in the frequency of genotypes (alleles) which can drastically reduce the transmission of the B and, when present in high frequency, can lead to its rapid loss. The frequency distribution of the ks of sons of F1 females from the cross L-230 x L-60 suggests that the two lines differ at two unlinked loci with additive effects on k. The genome of L-119 also caused the B to undergo nondisjunction in about 10% of the primary spermatocytes. A comparison between the ks of the males tested and those of males from a natural population suggests that in that population the B is "parasitic" and that the frequency of transmission-reducing genotypes is low.

Genotypes suppressing meiotic drive of a B chromosome in the mealybug, Pseudococcus obscurus

The rate of transmission (k) of a supernumerary B chromosome in male mealybugs is shown to depend strongly on the chromosome set of maternal origin. When both parents came from an isofemale line in which the frequency of the B chromosome increased rapidly and stabilized at a mean of more than 4.0 B chromosomes per individual, k was 0.92 and 0.95 in two series of crosses. However, when the female parent came from one of two isofemale lines in which the frequency of the B chromosome decreased from 2.0 to 0 in a few generations, k ranged from 0.53 to 0.78. The high ks, which represent a strong meiotic drive, are apparently responsible for the observed increase in the frequency of the B chromosome in several lines from a mean of about 0.5 to more than 4.0 in about 20 generations. The rapid loss of the B chromosome in other lines is attributed to genetic factors which caused the reduction in the rate of transmission of the B chromosome.