Sleep stage distribution in persons with mild traumatic brain injury: a polysomnographic study according to American Academy of Sleep Medicine standards

Concussion and the Sleeping Brain

BACKGROUND

Emerging research has suggested sleep to be a modifier of the trajectory of concussion recovery in adolescent and adult populations. Despite the growing recognition of the relationship between sleep and concussion, the mechanisms and physiological processes governing this association have yet to be established.

MAIN BODY

Following a concussion, a pathophysiologic cascade of events occurs, characterized by numerous factors including microglia activation, ionic imbalance, and release of excitatory neurotransmitters. Importantly, each of these factors plays a role in the regulation of the sleep-wake cycle. Therefore, dysregulation of sleep following injury may be a function of the diffuse disruption of cerebral functioning in the wake of both axonal damage and secondary physiological events. As the onset of sleep-related symptoms is highly variable following a concussion, clinicians should be aware of when and how these symptoms present. Post-injury changes in sleep have been reported in the acute, sub-acute, and chronic phases of recovery and can prolong symptom resolution, affect neurocognitive performance, and influence mood state. Though these changes support sleep as a modifier of recovery, limited guidance exists for clinicians or their patients in the management of sleep after concussion. This may be attributed to the fact that research has correlated sleep with concussion recovery but has failed to explain why the correlation exists. Sleep is a complex, multifactorial process and the changes seen in sleep that are seen following concussion are the result of interactions amongst numerous processes that regulate the sleep-wake cycle.

SHORT CONCLUSION

The assessment and management of sleep by identifying and considering the biological, sociological, and psychological interactions of this multifactorial process will allow for clinicians to address the dynamic nature of changes in sleep following concussion.

Sex Differences in Sleep Architecture After Traumatic Brain Injury: Potential Implications on Short-Term Episodic Memory and Recovery

Sleep-wake disturbances (SWDs) are common after TBI and often extend into the chronic phase of recovery. Such disturbances in sleep can lead to deficits in executive functioning, attention, and memory consolidation, which may ultimately impact the recovery process. We examined whether SWDs post-TBI were associated with morbidity during the post-acute period. Particular attention was placed on the impact of sleep architecture on learning and memory. Because women are more likely to report SWDs, we examined sex as a biological variable. We also examined subjective quality of life, depression, and disability levels. Data were retrospectively analyzed for 57 TBI patients who underwent an overnight polysomnography. Medical records were reviewed to determine cognitive and functional status during the period of the sleep evaluation. Consideration was given to medications, owing to the fact that a high number of these are likely to have secondary influences on sleep characteristics. Women showed higher levels of disability and reported more depression and lower quality of life. A sex-dependent disruption in sleep architecture was observed, with women having lower percent time in REM sleep. An association between percent time in REM and better episodic memory scores was found. Melatonin utilization had a positive impact on REM duration. Improvements in understanding the impact of sleep-wake disturbances on post-TBI outcome will aid in defining targeted interventions for this population. Findings from this study support the hypothesis that decreases in REM sleep may contribute to chronic disability and underlie the importance of considering sex differences when addressing sleep.

Sleep/Wake Disorders After Sports Concussion: Risks, Revelations, and Interventions

SUMMARY

Sleep-wake disturbances (SWDs) are among the most prevalent, persistent, and often disregarded sequelae of traumatic brain injury. Identification and treatment of SWDs in patients with traumatic brain injury is important and can complement other efforts to promote maximum functional recovery. SWDs can accentuate other consequences of traumatic brain injury, negatively affect mood, exacerbate pain, heighten irritability, and diminish cognitive abilities and the potential for recovery. The risk for sports injuries increases when athletes are sleep deprived. Sleep deprivation increases risk-taking behaviors, predisposing to injuries. SWDs are an independent risk factor for prolonged recovery after sports-related concussion. SWDs following sports-related concussion have been shown to impede recovery, rehabilitation, and return to preinjury activities.

Systematic Review of Sex and Gender Effects in Traumatic Brain Injury: Equity in Clinical and Functional Outcomes

Background: Although traumatic brain injury (TBI) is a leading cause of death and disability in male and female patients worldwide, little is known about the effect of sex and gender on TBI outcomes.

Objectives: This systematic review summarizes the evidence on the effect of sex and gender on core TBI outcomes.

Methods: All English-language studies from six literature databases that addressed core outcomes in adults with TBI and included sex or gender, TBI severity, and age in their analyses were considered eligible. Two reviewers extracted data, and two reviewers assessed study quality using tools recommended by the National Institutes of Health. The results were sorted according to time post-injury, injury severity, gender equity ranking of the study's country of origin, and outcomes studied. The results from the included studies were grouped based on the approach taken in reporting their respective findings.

Results and Limitations: Of 172 articles assessed, 58 studies were selected, comprising 1, 265, 955 participants with TBI (67% male across all studies) of all injury severities. All studies were conducted in countries with a very high or high human development index, while the Gender Inequality Index (GII) varied. While the heterogeneity across studies limited any meaningful conclusions with respect to the role of sex and gender, we did observe that as gender equality ranking improved, differences between male and female participants in outcomes would diminish. Inclusion of social equity parameters in the studies was limited.

Conclusions and Implications: The non-uniform findings observed bring forth the need to develop and use a comprehensive and consistent methodology in the study of sex and gender post-TBI, incorporating social equity parameters to uncover the potential social underpinnings of gender effects on health and functional outcomes.

Systematic Review Registration: CRD42018098697.

Traumatic Brain Injury and Incidence Risk of Sleep Disorders in Nearly 200,000 US Veterans

OBJECTIVE

To test the hypothesis that veterans with traumatic brain injury (TBI) have an increased subsequent risk of sleep disorders, we studied the longitudinal association between TBI and incident sleep disorders in nearly 200,000 veterans.

METHODS

We performed a cohort study of all patients diagnosed with a TBI in the Veterans Health Administration system from October 1, 2001, to September 30, 2015, who were age-matched 1:1 to veterans without TBI. Veterans with prevalent sleep disorders at baseline were excluded. Development of sleep disorders was defined as any inpatient or outpatient diagnosis of sleep apnea, hypersomnia, insomnia, or sleep-related movement disorders based on ICD-9 codes after the first TBI diagnosis or the random selection date for those without TBI. We restricted the analysis to those with at least 1 year of follow-up. We used Cox proportional hazards models to examine the association between TBI and subsequent risk of sleep disorders.

RESULTS

The study included 98,709 veterans with TBI and 98,709 age-matched veterans without TBI (age 49 ± 20 years). After an average follow-up of 5 (1-14) years, 23,127 (19.6%) veterans developed sleep disorders. After adjustment for demographics, education, income, and medical and psychiatric conditions, those who had TBI compared to those without TBI were 41% more likely to develop any sleep disorders (hazard ratio 1.41 [95% confidence interval 1.37-1.44]), including sleep apnea (1.28 [1.24-1.32]), insomnia (1.50 [1.45-1.55]), hypersomnia (1.50 [1.39-1.61]), and sleep-related movement disorders (1.33 [1.16-1.52]). The association was stronger for mild TBIs, did not differ appreciably by presence of posttraumatic stress disorder, and remained after a 2-year time lag.

CONCLUSION

In 197,418 veterans without sleep disorders, those with diagnosed TBI had an increased risk of incident sleep disorders over 14 years. Improved prevention and long-term management strategies for sleep are needed for veterans with TBI.

Misperception of sleep duration in mild traumatic brain injury/concussion: a preliminary report

Background: Polysomnographic (PSG) findings of persons with mild traumatic brain injury (mTBI)/concussion show longer total sleep time than patients themselves report; the reason for this is not entirely clear.Objective: This study aimed to elucidate the socio-demographic, brain-injury-related, and clinical characteristics that underlie accuracy of sleep duration reporting in mTBI/concussion.Methods: Thirty-seven participants diagnosed with mTBI/concussion (57% male, 47.54 ± 11.3 years old) underwent clinical and neuroimaging examinations, full-night PSG, and estimated sleep duration following PSG.Results: Mean self-reported sleep duration was 342 ± 93.6 minutes and PSG-measured sleep duration was 382 ± 76.8 minutes. Measurements were moderately correlated (rho = 0.46, p = .004). Age associated with self- and PSG-measured sleep duration (rho = 0.34 and rho = 0.84, respectively, p < .05). Self-reported sleep duration was uniquely associated with insomnia severity (rho = -0.48, p = .002). In the fully adjusted multivariable regression analysis, several clinical characteristics of patients explained 30% of the discrepancy between self- and PSG-measured sleep duration.Conclusion: The observed results indicate that persons with mTBI do not accurately assess their sleep duration and, therefore, PSG is warranted in clinical situations where sleep duration is of concern.

Concussion Management Practices for Youth Who Are Slow to Recover: A Survey of Canadian Rehabilitation Clinicians

Purpose: The objective of this study was to estimate the scope of concussion management practices for youth used by Canadian rehabilitation clinicians. A secondary objective was to determine the use of aerobic exercise as a management strategy. Method: Members of the Canadian Association of Occupational Therapists, Canadian Athletic Therapists Association, and Canadian Physiotherapy Association were invited to participate in an online cross-sectional survey. Two clinical vignettes were provided with a brief history. The respondents were asked about the type of treatments they would provide (e.g., manual therapy, education, aerobic exercise, return-to-learn or return-to-play protocol, goal setting). Results: The survey was completed by 555 clinicians. The top five treatment options were education, sleep recommendations, goal setting, energy management, and manual therapy. Just more than one-third of the clinicians prescribed aerobic exercise. Having a high caseload of patients with concussion (75%-100%) was a significant predictor of prescribing aerobic exercise. Conclusions: A wide variety of treatment options were selected, although the most common were education, sleep recommendations, energy management, and goal setting. Few clinicians used aerobic exercise as part of their concussion management strategy.

Sleep before and after work-related concussion: Sex differences in effects and functional outcomes

BACKGROUND

Recent studies have started disentangling components of disturbed sleep as part of the post-concussive syndrome, but little is known about the workers with an injury' perspectives on post-injury sleep changes or what causes these changes.

OBJECTIVES

To determine the effects of work-related concussion/mild traumatic brain injury (wr-mTBI) on perceptions of refreshing sleep in workers with an injury and to identify the relevant factors responsible for sleep changes.

METHODS

We studied post-concussive changes in sleep in 66 adults (50% male workers, 42% aged 30-50 years, median post-injury days: 155) who had sustained wr-mTBI and experienced functional limitations long after the injury. We collected sociodemographic, occupational and health status data and identified variables related to post-concussive changes in refreshing sleep.

RESULTS

Forty-seven workers with wr-mTBI (79% of male workers, 64% of female workers) perceived their sleep as being refreshing before injury and unrefreshing afterwards (χ2 = 67.70 for change, χ2 = 27.6 for female and χ2 = 41.1 for male workers, p < 0.0001). Post-concussive losses in refreshing sleep were associated with socio demographic, occupational, and health status data variables. Sex stratification revealed differences between male and female workers.

CONCLUSIONS

Workers with wr-mTBI experience clinically meaningful changes in refreshing sleep that are associated with modifiable variables. The observed differences in functional outcomes between male and female workers warrant further study.

Sleep and stress in the acute phase of concussion in youth

This study sought to address the complex interplay between both biological and psychological perceptions of stress and sleep in the acute stages following a mild traumatic brain injury. A secondary goal was to identify potential targets for intervention. Eleven acutely injured youth (mean age 12 years) were studied at home with overnight actigraphy, salivary cortisol and melatonin assays, and subjective ratings of stress and fatigue (injured group). Nine matched control youth also were assessed (control group). Results suggested longer sleep latencies (time to fall asleep) and higher levels of fatigue in the injured group exist (p = 0.025 and p = 0.004, respectively). In the injured group, stress and sleep onset were significantly related with most subjects meeting criteria for Acute Stress Disorder. Melatonin levels were lower at bedtime in the injured group. Saliva samples were collected via passive drool at three time points: ∼1 h before bed (“bedtime” or T1), immediately upon waking (time 2: T2), and 30 min post-waking (time 3: T3). Overnight increases in cortisol (T1 to T2) were greater for the injured group; however, post-sleep changes in cortisol (T2 to T3) were reversed with control concentrations increasing. These findings are unique in using actigraphy and salivary hormone levels in an acutely injured youth while in their homes. The differences in sleep latency and the presence of injury-related stress point to potential treatment targets in acute concussion.

Sleep disturbances among older adults following traumatic brain injury

Sleep disturbances are common sequelae of traumatic brain injury (TBI) that are associated with poorer recovery. This is important among older adults, who fare worse following TBI relative to younger adults and have a higher prevalence of sleep disorders. The objective of this study was to assess the risk of newly-diagnosed sleep disorders following TBI among adults ≥65 years. Using a large commercial insurance database, older adults diagnosed with TBI between 2008-2014 (n = 78,044) and non-TBI controls (n = 76,107) were identified. The first dates of diagnosis of four common sleep disorders (hypersomnia, insomnia, obstructive sleep apnea, and restless legs syndrome) and a composite of any sleep disorder were identified. To compare groups, this study used a difference-in-differences (DID) approach, accounting for pre-index differences between cohorts and the trends in sleep diagnoses over time. Individuals with TBI were more likely to have any newly-diagnosed sleep disorder before (14.1% vs 9.4%, p < 0.001) and after (22.7% vs 14.1%, p < 0.001) the index date. In fully adjusted DID models, TBI was associated with an increased risk of insomnia (rate ratio (RR) = 1.17; 95% confidence interval (CI) = 1.08-1.26) and any sleep disorder (RR = 1.13; 95% CI = 1.08-1.19). Following TBI among older adults, screening and education on sleep disorders should be considered.

Sleep problems contribute to post-concussive symptoms in service members with a history of mild traumatic brain injury without posttraumatic stress disorder or major depressive disorder

BACKGROUND:

Many with a history of mild traumatic brain injury (TBI) experience sleep problems, which are also common symptoms of stress-related and mood disorders.

OBJECTIVE:

To determine if sleep problems contributed unique variance to post-concussive symptoms above and beyond symptoms of posttraumatic stress disorder/major depressive disorder (PTSD/MDD) after mild TBI.

METHODS:

313 active duty service members with a history of mild TBI completed sleep, PTSD, and mood symptom questionnaires, which were used to determine contributions to the Neurobehavioral Symptom Inventory.

RESULTS:

59% of the variance in post-concussive symptoms were due to PTSD symptom severity while depressive symptoms and sleep problems contributed an additional 1% each. This pattern differed between those with and without clinical diagnosis of PTSD/MDD. For those with PTSD/MDD, PTSD and depression symptoms but not sleep contributed to post-concussive symptoms. For those without PTSD/MDD, PTSD symptoms and sleep contributed specifically to somatosensory post-concussive symptoms. Daytime dysfunction and sleep disturbances were associated with post-concussive symptoms after PTSD and depression symptoms were controlled.

CONCLUSIONS:

PTSD symptom severity explained the most variance for post-concussive symptoms among service members with a history of mild TBI, while depression symptoms, daytime dysfunction, and sleep disturbances independently contributed small amounts of variance.

Sex Differences in Traumatic Brain Injury: What We Know and What We Should Know

There is growing recognition of the problem of male bias in neuroscience research, including in the field of traumatic brain injury (TBI) where fewer women than men are recruited to clinical trials and male rodents have predominantly been used as an experimental injury model. Despite TBI being a leading cause of mortality and disability worldwide, sex differences in pathophysiology and recovery are poorly understood, limiting clinical care and successful drug development. Given growing interest in sex as a biological variable affecting injury outcomes and treatment efficacy, there is a clear need to summarize sex differences in TBI. This scoping review presents an overview of current knowledge of sex differences in TBI and a comparison of human and animal studies. We found that overall, human studies report worse outcomes in women than men, whereas animal studies report better outcomes in females than males. However, closer examination shows that multiple factors including injury severity, sample size, and experimental injury model may differentially interact with sex to affect TBI outcomes. Additionally, we explore how sex differences in mitochondrial structure and function might contribute to possible sex differences in TBI outcomes. We propose recommendations for future investigations of sex differences in TBI, which we hope will lead to improved patient management, prognosis, and translation of therapies from bench to bedside.

Persistent impairment based symptoms post mild traumatic brain injury: Does a standard symptom scale detect them?

AIM

To further explore symptoms in patients beyond the expected recovery period post mild Traumatic Brain Injury (mTBI) that are potentially indicative of impairment.

METHODS

Ninety-four individuals (62 diagnosed with mTBI within the previous 4-24 weeks and 32 healthy controls) participated in the study. Participants in the mTBI group were further grouped as symptomatic (n = 33) or asymptomatic (n = 29) based on their spontaneous report of symptoms at the time of screening. Measures included a demographic questionnaire, 8 impairment specific self-report clinical tools, and a standard post-mTBI self-report symptom scale (Head Injury Scale (HIS)).

RESULTS

Compared to the control group, scores for all instruments (including the HIS) were higher in the symptomatic mTBI group (P < 0.05), and higher for the neck disability and hyperarousal measures in the asymptomatic mTBI group (p < 0.035), but not the HIS (p > 0.093). Overall 94% of the symptomatic and 62% of the asymptomatic participants post-mTBI, recorded scores considered to be clinically relevant on at least one impairment screening tool. In contrast, only 28% of the asymptomatic mTBI group recorded a clinically relevant score for the HIS.

CONCLUSION

Symptoms indicative of persisting impairments beyond the expected recovery period were apparent in a substantial proportion of individuals post mTBI. Furthermore, a high percentage of individuals initially reporting as symptom free demonstrated clinically relevant scores on at least one impairment screening tool. Findings also suggest that a standard post-mTBI self-report symptom scale may often not detect the presence of persisting symptoms.

Hypocretin Mediates Sleep and Wake Disturbances in a Mouse Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is a major cause of disability worldwide. Post-TBI sleep and wake disturbances are extremely common and difficult for patients to manage. Sleep and wake disturbances contribute to poor functional and emotional outcomes from TBI, yet effective therapies remain elusive. A more comprehensive understanding of mechanisms underlying post-TBI sleep and wake disturbance will facilitate development of effective pharmacotherapies. Previous research in human patients and animal models indicates that altered hypocretinergic function may be a major contributor to sleep-wake disturbance after TBI. In this study, we further elucidate the role of hypocretin by determining the impact of TBI on sleep-wake behavior of hypocretin knockout (HCRT KO) mice. Adult male C57BL/6J and HCRT KO mice were implanted with electroencephalography recording electrodes, and pre-injury baseline recordings were obtained. Mice were then subjected to either moderate TBI or sham surgery. Additional recordings were obtained and sleep-wake behavior determined at 3, 7, 15, and 30 days after TBI or sham procedures. At baseline, HCRT KO mice had a significantly different sleep-wake phenotype than control C57BL/6J mice. Post-TBI sleep-wake behavior was altered in a genotype-dependent manner: sleep of HCRT KO mice was not altered by TBI, whereas C57BL/6J mice had more non-rapid eye movement sleep, less wakefulness, and more short wake bouts and fewer long wake bouts. Numbers of hypocretin-positive cells were reduced in C57BL/6J mice by TBI. Collectively, these data indicate that the hypocretinergic system is involved in the alterations in sleep-wake behavior that develop after TBI in this model, and suggest potential therapeutic interventions.

Physiological and pathological covariates of persistent concussion-related fatigue: results from two regression methodologies

BACKGROUND

Fatigue severity in persons with mild traumatic brain injury (mTBI) has received little research attention, despite its typically positively skewed nature. Investigation of covariates across a range of fatigue severity may provide insight into important contributors.

OBJECTIVE

To assess the relative significance of a priori-hypothesized covariates of physiological and pathological (mental and physical) fatigue in persons with mTBI/concussion, applying ordinary least squares (OLS) and quantile regression (QR) approaches.

METHODS

We conducted a cross-sectional investigation in 80 participants with mTBI/concussion (mean age 45.4 ± 10.1 years, 59% male). The fatigue severity scale (FSS) was used as an outcome measure. Predictors of this outcome, grouped into physiological and pathological models of fatigue were assessed using OLS and QR.

RESULTS

The mean total FSS score was 46.13 ± 14.59, and the median was 49 (interquartile range 37-57), demonstrating positive skewness. Fatigue severity was associated with variables within the mental, psychological and psychiatric domains at different levels of the fatigue score distribution.

CONCLUSION

Results highlighted that some covariates had a significant impact on the FSS total score at non-central parts of its distribution, while others exhibited significant impact across the entire distribution. Addressing covariates of fatigue across the severity continuum can enhance research and clinical management.

Evaluation of Home Polysomnography Findings, Quality of Sleep, and Fatigue in Inflammatory Bowel Disease: A Case Series

STUDY OBJECTIVES

The pathogenesis of inflammatory bowel disease (IBD) is not well understood, and sleep disorders may be potential triggers for IBD. Thus, an evaluation of the sleep characteristics, fatigue symptoms, and cytokine levels was performed in patients with IBD during periods of active disease and remission.

METHODS

A total of 20 participants presenting with Crohn's disease or ulcerative colitis, with active disease (n = 7) or in remission (n = 13), underwent home polysomnography (H-PSG). Pittsburgh Sleep Quality Index (PSQI) and Modified Fatigue Impact Scale (MFIS) were applied, in addition to the evaluation of interleukin (IL)-6, IL-10, and tumor necrosis factor alpha (TNF-α) serum levels. Exploratory analysis, t test and Mann-Whitney U test were used.

RESULTS

The mean sleep latency in patients with active disease was 133.07 minutes and 106.79 minutes in those in remission. The sleep efficiency and sleep fragmentation in patients with active disease and those in remission were 80.90% and 84.20% (median), and 76.36/min and 69.82/min (mean), respectively, although the H-PSG parameters did not differ between the groups. The PSQI scores indicated poor sleep quality (global score above 5) in all participants with IBD, and the participants with active disease presented more symptoms of fatigue (P = .032). IL-6 and TNF-α average levels were higher in the participants with disease remission, although with a larger dispersion of the data.

CONCLUSIONS

No significant difference in the H-PSG characteristics was observed between the patients with IBD with active disease and those in remission; however, the perception of the participants with IBD showed significant effect on the sleep quality and fatigue symptoms.

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.

Electrophysiological testing in concussion: A guide to clinical applications

The diagnosis of mild traumatic brain injury in concussion is difficult since it is often unwitnessed, the patient’s recall is unreliable and initial clinical examination is often unrevealing, correlating poorly with the extent of brain injury. At present, there are no objective biomarkers of mild traumatic brain injury in concussion. Thus, a sensitive gold standard test is required to enable the effective and safe triage of patients who present to the acute services. As well as triage, objective monitoring of patients’ recovery over time and separate from clinical features that patients may develop following the injury (e.g. depression and migraine) is also needed. In contrast to neuroimaging, which is widely used to investigate traumatic brain injury patients, electrophysiology is readily available, is cheap and there are internationally recognized standardised methodologies. Herein, we review the existing literature on electrophysiological testing in concussion and mild traumatic brain injury; specifically, electroencephalogram, polysomnography, brainstem auditory evoked potentials, electro- and videonystagmography, vestibular evoked myogenic potentials, visually evoked potentials, somatosensory evoked potentials and transcranial magnetic stimulation.

Gender Disparities in Trauma Care: How Sex Determines Treatment, Behavior, and Outcome

Trauma data bank and other research reveal sex disparities in trauma care. Risk-taking behaviors leading to traumatic injury have been associated with sex, menstrual cycle timing, and cortisol levels. Trauma patient treatment stratified by sex reveals differences in access to services at trauma centers as well as specific treatments, such as venous thromboembolism prophylaxis and massive transfusion component ratios. Trauma patient outcomes, such as in-hospital mortality, multiple organ failure, pneumonia, and sepsis are associated with sex disparities in the general trauma patient. Outcome after general trauma and specifically traumatic brain injury show mixed results with respect to sex disparity.

Potential for the development of light therapies in mild traumatic brain injury

Light affects almost all aspects of human physiological functioning, including circadian rhythms, sleep-wake regulation, alertness, cognition and mood. We review the existing relevant literature on the effects of various wavelengths of light on these major domains, particularly as they pertain to recovery from mild traumatic brain injuries. Evidence suggests that light, particularly in the blue wavelengths, has powerful alerting, cognitive and circadian phase shifting properties that could be useful for treatment. Other wavelengths, such as red and green may also have important effects that, if targeted appropriately, might also be useful for facilitating recovery. Despite the known effects of light, more research is needed. We recommend a personalized medicine approach to the use of light therapy as an adjunctive treatment for patients recovering from mild traumatic brain injury.

Sleep, Sleep Disorders, and Circadian Health following Mild Traumatic Brain Injury in Adults: Review and Research Agenda

A rapidly expanding scientific literature supports the frequent co-occurrence of sleep and circadian disturbances following mild traumatic brain injury (mTBI). Although many questions remain unanswered, the preponderance of evidence suggests that sleep and circadian disorders can result from mTBI. Among those with mTBI, sleep disturbances and clinical sleep and circadian disorders contribute to the morbidity and long-term sequelae across domains of functional outcomes and quality of life. Specifically, along with deterioration of neurocognitive performance, insufficient and disturbed sleep can precede, exacerbate, or perpetuate many of the other common sequelae of mTBI, including depression, post-traumatic stress disorder, and chronic pain. Further, sleep and mTBI share neurophysiologic and neuroanatomic mechanisms that likely bear directly on success of rehabilitation following mTBI. For these reasons, focus on disturbed sleep as a modifiable treatment target has high likelihood of improving outcomes in mTBI. Here, we review relevant literature and present a research agenda to 1) advance understanding of the reciprocal relationships between sleep and circadian factors and mTBI sequelae and 2) advance rapidly the development of sleep-related treatments in this population.

Sex & gender considerations in concussion research

The study of concussion, a common form of mild traumatic brain injury, has received increased notice over the last decade. Recently, more researchers have been addressing the historic paucity of attention over sex and gender influences on recovery outcomes after concussion. This development has led to exciting progress in our understanding of concussion incidence and outcomes. In this review, we will report on new findings from varying studies on sex differences in the epidemiology of concussion and clinical manifestations of mild traumatic brain injury/concussion, further discussing some key issues related to the integration of sex and gender in concussion research in a broad range of contexts, with recommendations to guide future research, along with sex- and gender-sensitive policy considerations.

Sleep and Psychiatric Disorders in Persons With Mild Traumatic Brain Injury

Mild traumatic brain injury (mTBI) frequently challenges the integrity of sleep function by affecting multiple brain areas implicated in controlling the switch between wakefulness and sleep and those involved in circadian and homeostatic processes; the malfunction of each causes a variety of disorders. In this review, we discuss recent data on the dynamics between disorders of sleep and mental/psychiatric disorders in persons with mTBI. This analysis sets the stage for understanding how a variety of physiological, emotional and environmental influences affect sleep and mental activities after injury to the brain. Consideration of the intricate links between sleep and mental functions in future research can increase understanding on the underlying mechanisms of sleep-related and psychiatric comorbidity in mTBI.