Sleep-wake disturbances in hospitalized patients with traumatic brain injury: association with brain trauma but not with an abnormal melatonin circadian rhythm

Sleep Disturbance During Post-Traumatic Amnesia and Early Recovery After Traumatic Brain Injury

After moderate to severe traumatic brain injury (TBI), sleep disturbance commonly emerges during the confused post-traumatic amnesia (PTA) recovery stage. However, the evaluation of early sleep disturbance during PTA, its recovery trajectory, and influencing factors is limited. This study aimed to evaluate sleep outcomes in patients experiencing PTA using ambulatory gold-standard polysomnography (PSG) overnight and salivary endogenous melatonin (a hormone that influences the sleep-wake cycle) assessment at two time-points. The relationships between PSG-derived sleep-wake parameters and PTA symptoms (i.e., agitation and cognitive disturbance) were also evaluated. In a patient subset, PSG was repeated after PTA had resolved to assess the trajectory of sleep disturbance. Participants with PTA were recruited from Epworth HealthCare's inpatient TBI Rehabilitation Unit. Trained nurses administered overnight PSG at the patient bedside using the Compumedics Somté portable PSG device (Compumedics, Ltd., Australia). Two weeks after PTA had resolved, PSG was repeated. On a separate evening, two saliva specimens were collected (at 24:00 and 06:00) for melatonin testing. Results of routine daily hospital measures (i.e., Agitated Behavior Scale and Westmead PTA Scale) were also collected. Twenty-nine patients were monitored with PSG (mean: 41.6 days post-TBI; standard deviation [SD]: 28.3). Patients' mean sleep duration was reduced (5.6 h, SD: 1.2), and was fragmented with frequent awakenings (mean: 27.7, SD: 15.0). Deep, slow-wave restorative sleep was reduced, or completely absent (37.9% of patients). The use of PSG did not appear to exacerbate patient agitation or cognitive disturbance. Mean melatonin levels at both time-points were commonly outside of normal reference ranges. After PTA resolved, patients (n = 11) displayed significantly longer mean sleep time (5.3 h [PTA]; 6.5 h [out of PTA], difference between means: 1.2, p = 0.005). However, disturbances to other sleep-wake parameters (e.g., increased awakenings, wake time, and sleep latency) persisted after PTA resolved. This is the first study to evaluate sleep disturbance in a cohort of patients as they progressed through the early TBI recovery phases. There is a clear need for tailored assessment of sleep disturbance during PTA, which currently does not form part of routine hospital assessment, to suggest new treatment paradigms, enhance patient recovery, and reduce its long-term impacts.

Transcutaneous auricular vagus nerve stimulation in the treatment of disorders of consciousness: mechanisms and applications

This review provides an in-depth exploration of the mechanisms and applications of transcutaneous auricular vagus nerve stimulation (taVNS) in treating disorders of consciousness (DOC). Beginning with an exploration of the vagus nerve's role in modulating brain function and consciousness, we then delve into the neuroprotective potential of taVNS demonstrated in animal models. The subsequent sections assess the therapeutic impact of taVNS on human DOC, discussing the safety, tolerability, and various factors influencing the treatment response. Finally, the review identifies the current challenges in taVNS research and outlines future directions, emphasizing the need for large-scale trials, optimization of treatment parameters, and comprehensive investigation of taVNS's long-term effects and underlying mechanisms. This comprehensive overview positions taVNS as a promising and safe modality for DOC treatment, with a focus on understanding its intricate neurophysiological influence and optimizing its application in clinical settings.

Sleep Disruptions in Hospitalized Adults Sustaining a Traumatic Brain Injury: A Scoping Review

OBJECTIVE

Adults sustaining a traumatic brain injury (TBI) are at risk of sleep disturbances during their recovery, including when such an injury requires hospitalization. However, the sleep-wake profile, and internal and external factors that may interfere with sleep initiation/maintenance in hospitalized TBI patients are poorly understood. This review aimed to: (1) identify/summarize the existing evidence regarding sleep and sleep measurements in TBI adults receiving around-the-clock care in a hospital or during inpatient rehabilitation, and (2) identify internal/external factors linked to poor sleep in this context.

METHODS

A scoping review was conducted in accordance with the PRISMA Scoping Review Extension guidelines. A search was conducted in MEDLINE, PsycINFO, CINAHL, and Web of Science databases.

RESULTS

Thirty relevant studies were identified. The most common sleep variables that were put forth in the studies to characterize sleep during hospitalization were nighttime sleep time (mean = 6.5 hours; range: 5.2-8.9 hours), wake after sleep onset (87.1 minutes; range: 30.4-180 minutes), and sleep efficiency (mean = 72.9%; range: 33%-96%) using mainly actigraphy, polysomnography, and questionnaires (eg, the sleep-wake disturbance item of the Delirium Rating Scale or the Pittsburgh Sleep Quality Index). Twenty-four studies (80%) suggested that hospitalized TBI patients do not get sufficient nighttime sleep, based on the general recommendations for adults (7-9 hours per night). Sleep disruptions during hospitalization were found to be associated to several internal factors including TBI severity, cognitive status, and analgesia intake. External and modifiable factors, such as noise, light, and patient care, were consistently associated with sleep disruptions in this context.

CONCLUSION

Although the literature on sleep disturbances in hospitalized TBI patients has been increasing in recent years, many gaps in knowledge remain, including phenotypes and risk factors. Identifying these factors could help clinicians better understand the multiple sources of TBI patients' sleep difficulties and intervene accordingly.

The growing gap: A study of sleep, encoding, and consolidation of new words in chronic traumatic brain injury

Word learning is an iterative and dynamic process supported by multiple neural and cognitive systems. Converging evidence from behavioral, cellular, and systems neuroscience highlights sleep as an important support for memory and word learning over time. In many lab-based word learning experiments, participants encode and subsequently retrieve newly learned words in a single session. These designs are inadequate to capture the full dynamic word learning process, making them less ecologically valid. Single timepoint studies also limit investigation of the role of behavioral and lifestyle factors, like sleep, in supporting word learning over time. Adults with a history of traumatic brain injury (TBI), who commonly exhibit deficits in the memory systems that support word learning and report concomitant sleep disturbance, provide a unique opportunity to examine the link between memory, sleep, and word learning. Here we examined word learning over time and the influence of sleep on short- and long-term word recall in 50 adults with chronic moderate-severe TBI and 50 demographically matched neurotypical peers. We used a randomized within-participant crossover design to assess immediate encoding of new words and the consolidation of those words over time across intervals that did or did not involve sleep. Participants completed this study over the course of two weeks in their own homes to capture the iterative, dynamic process of real-world word learning. We also measured sleep in free living conditions using actigraphy throughout the experiment. Participants with TBI exhibited a word learning deficit that began at encoding and persisted across time. Critically, this deficit grew over the course of the week. The performance gap between groups was larger at the 1-week post-test than the immediate post-test, suggesting deficits in both encoding and consolidation of new words in individuals with TBI. Participants with and without TBI remembered more words when they slept after learning. Ecologically valid research designs that examine the relationship between memory, sleep, and word learning over time promise to advance mechanistic accounts of word learning and improve the long-term retention of new words in individuals with and without brain injury.

Traumatic Brain Injury, Sleep, and Melatonin-Intrinsic Changes with Therapeutic Potential

Traumatic brain injury (TBI) is one of the most prevalent causes of morbidity in the United States and is associated with numerous chronic sequelae long after the point of injury. One of the most common long-term complaints in patients with TBI is sleep dysfunction. It is reported that alterations in melatonin follow TBI and may be linked with various sleep and circadian disorders directly (via cellular signaling) or indirectly (via free radicals and inflammatory signaling). Work over the past two decades has contributed to our understanding of the role of melatonin as a sleep regulator and neuroprotective anti-inflammatory agent. Although there is increasing interest in the treatment of insomnia following TBI, a lack of standardization and rigor in melatonin research has left behind a trail of non-generalizable data and ambiguous treatment recommendations. This narrative review describes the underlying biochemical properties of melatonin as they are relevant to TBI. We also discuss potential benefits and a path forward regarding the therapeutic management of TBI with melatonin treatment, including its role as a neuroprotectant, a somnogen, and a modulator of the circadian rhythm.

Sleep from acute to chronic traumatic brain injury and cognitive outcomes

STUDY OBJECTIVES

Traumatic brain injuries (TBIs) cause persistent cerebral damage and cognitive deficits. Because sleep may be a critical factor for brain recovery, we characterized the sleep of patients with TBI from early hospitalization to years post-injury and explored the hypothesis that better sleep during hospitalization predicts more favorable long-term cognitive outcomes.

METHODS

We tested patients with moderate-to-severe TBI in the hospitalized (n = 11) and chronic (n = 43) stages using full-night polysomnography, with 82% of the hospitalized group being retested years post-injury. Hospitalized patients with severe orthopedic and/or spinal cord injury (n = 14) and healthy participants (n = 36) were tested as controls for the hospitalized and chronic TBI groups, respectively. Groups had similar age and sex and were compared for sleep characteristics, including slow waves and spindles. For patients with TBI, associations between sleep during hospitalization and long-term memory and executive function were assessed.

RESULTS

Hospitalized patients with TBI or orthopedic injuries had lower sleep efficiency, higher wake after sleep onset, and lower spindle density than the chronic TBI and healthy control groups, but only hospitalized patients with brain injury had an increased proportion of slow-wave sleep. During hospitalization for TBI, less fragmented sleep, more slow-wave sleep, and higher spindle density were associated to more favorable cognitive outcomes years post-injury, while injury severity markers were not associated with these outcomes.

CONCLUSION

These findings highlight the importance of sleep following TBI, as it could be a strong predictor of neurological recovery, either as a promoter or an early marker of cognitive outcomes.

Sleep assessment in critically ill adults: A systematic review and meta-analysis

PURPOSE

To systematically review sleep evaluation, characterize sleep disruption, and explore effects of sleepdisruption on outcomes in adult ICU patients.

MATERIALS AND METHODS

We systematically searched databases from May 1969 to June 2021 (PROSPERO protocol number: CRD42020175581). Prospective and retrospective studies were included studying sleep in critically ill adults, excluding patients with sleep or psychiatric disorders. Meta-regression methods were applied when feasible.

RESULTS

132 studies (8797 patients) were included. Fifteen sleep assessment methods were identified, with only two validated. Patients had significant sleep disruption, with low sleep time, and low proportion of restorative rapid eye movement (REM). Sedation was associated with higher sleep efficiency and sleep time. Surgical versus medical patients had lower sleep quality. Patients on ventilation had a higher amount of light sleep. Meta-regression only suggested an association between total sleep time and occurrence of delirium (p < 0.001, 15 studies, 519 patients). Scarce data precluded further analyses. Sleep characterized with polysomnography (PSG) correlated well with actigraphy and Richards Campbell Sleep Questionnaire (RCSQ).

CONCLUSIONS

Sleep in critically ill patients is severely disturbed, and actigraphy and RCSQ seem reliable alternatives to PSG. Future studies should evaluate impact of sleep disruption on outcomes.

Sleep disturbance mediates the link between childhood trauma and clinical outcome in severe mental disorders

BACKGROUND

The experience of childhood trauma is linked to more severe symptoms and poorer functioning in severe mental disorders; however, the mechanisms behind this are poorly understood. We investigate the relationship between childhood trauma and sleep disturbances in severe mental disorders including the role of sleep disturbances in mediating the relationship between childhood trauma and the severity of clinical symptoms and poorer functioning.

METHODS

In total, 766 participants with schizophrenia-spectrum (n = 418) or bipolar disorders (n = 348) were assessed with the Childhood Trauma Questionnaire. Sleep disturbances were assessed through the sleep items in the self-reported Inventory of Depressive Symptoms. Clinical symptoms and functioning were assessed with The Positive and Negative Syndrome Scale and the Global Assessment of Functioning Scale. Mediation analyses using ordinary least squares regression were conducted to test if sleep disturbances mediated the relationship between childhood trauma and the severity of clinical symptoms and poorer functioning.

RESULTS

Symptoms of insomnia, but not hypersomnia or delayed sleep phase, were significantly more frequent in participants with childhood trauma experiences compared to those without. Physical abuse, emotional abuse, and emotional neglect were significantly associated with insomnia symptoms. Insomnia symptoms partly mediate the relationship between childhood trauma and the severity of positive and depressive/anxiety symptoms, in addition to poorer functioning.

CONCLUSION

We found frequent co-occurrence of childhood trauma history and current insomnia in severe mental disorders. Insomnia partly mediated the relationship between childhood trauma and the severity of clinical symptoms and functional impairment.

Prognostic Value of Circadian Rhythm of Brain Temperature in Traumatic Brain Injury

Hypothermia has been used in postoperative management of traumatic brain injury (TBI); however, the rhythmic variation and prognostic value of brain temperature after TBI have never been studied. This study describes diurnal brain temperature patterns in comatose patients with TBI. Mesors of brain temperature, amplitude, and acrophase were estimated from recorded temperature measurements using cosinor analysis. The association of these patterns with clinical parameters, mortality, and functional outcomes in a 12-month follow-up was examined. According to the cosinor analysis, 59.3% of patients presented with circadian rhythms of brain temperature in the first 72 h postoperatively. The rhythm-adjusted mesor of brain temperature was 37.39 ± 1.21 °C, with a diminished mean amplitude of 0.28 (±0.25) °C; a shift of temperature acrophase was also observed. Multivariate logistic regression analysis revealed that initial Glasgow coma scale score, age, elevated blood glucose level, and circadian rhythm of brain temperature seemed to be predictive and prognostic factors of patients' functional outcomes. For the prediction of survival status, younger patients or those patients with mesor within the middle 50% of brain temperature were more likely to survive. The analysis of brain temperature rhythms in patients with moderate and severe TBI provided additional predictive information related to mortality and functional outcomes.

Melatonin Represses Mitophagy to Protect Mouse Granulosa Cells from Oxidative Damage

Various environmental stimuli, including oxidative stress, could lead to granulosa cell (GC) death through mitophagy. Recently, it was reported that melatonin (MEL) has a significant effect on GC survival during oxidative damage. Here, we found that MEL inhibited oxidative stress-induced mitophagy to promote GC survival. The loss of cell viability upon H₂O₂ exposure was significantly restored after MEL treatment. Concomitantly, MEL inhibited the activation of mitophagy during oxidative stress. Notably, blocking mitophagy repressed GC death caused by oxidative stress. However, MEL cannot further restore viability of cells treated with mitophagy inhibitor. Moreover, PTEN-induced putative kinase 1 (PINK1), a mitochondrial serine/threonine-protein kinase, was inhibited by MEL during oxidative stress. As a result, the E3 ligase Parkin failed to translocate to mitochondria, leading to impaired mitochondria clearance. Using RNAi to knock down PINK1 expression, we further verified the role of the MEL-PINK1-Parkin (MPP) pathway in maintaining GC survival by suppressing mitophagy. Our findings not only clarify the protective mechanisms of MEL against oxidative damage in GCs, but also extend the understanding about how circadian rhythms might influence follicles development in the ovary. These findings reveal a new mechanism of melatonin in defense against oxidative damage to GCs by repressing mitophagy, which may be a potential therapeutic target for anovulatory disorders.

Assessing Sleep Architecture With Polysomnography During Posttraumatic Amnesia After Traumatic Brain Injury: A Pilot Study

BACKGROUND

Early-onset sleep disturbance is common following moderate to severe traumatic brain injury (TBI) and often emerges while patients are in posttraumatic amnesia (PTA). However, sleep disruptions during this subacute recovery phase are not well-defined, and research often utilizes indirect measures (actigraphy) that quantify sleep based on activity. This study aims to examine sleep macro-architecture and sleep quality directly with ambulatory polysomnography (PSG) and measure endogenous salivary melatonin levels for patients experiencing PTA following moderate to severe TBI.

METHOD

Participants were recruited from an inpatient TBI rehabilitation unit. Nighttime PSG was administered at the patient's bedside. Two saliva specimens were collected for melatonin testing on a separate evening (24:00 and 06:00 hours) using melatonin hormone profile test kits.

RESULTS

Of 27 patients in whom PSG was recorded, the minimum required monitoring time occurred in n =17 (adherence: 63%) at a median of 37.0 days (quartile 1 [Q1] to quartile 3 [Q3]: 21.5-50.5) postinjury. Median non-rapid eye movement (NREM) and REM sleep proportions were similar to normal estimates. Slow-wave sleep was reduced and absent in 35.3% of patients. Sleep periods appeared fragmented, and median sleep efficiency was reduced (63.4%; Q1-Q3: 55.1-69.2). Median melatonin levels at both timepoints were outside the normal range of values specified for this test (from Australian Clinical Labs).

CONCLUSION

This study reports that ambulatory PSG and salivary melatonin assessment are feasible for patients experiencing PTA and offers new insight into the extent of sleep disturbance. Further research is necessary to understand associations between PTA and sleep disturbance.

Sleep and Activity Patterns Are Altered During Early Critical Illness in Mechanically Ventilated Adults

BACKGROUND

Mechanically ventilated (MV) patients in the intensive care unit (ICU) often experience disturbed sleep and profound inactivity.

OBJECTIVES

The aim of this study was to report 5 consecutive days' descriptive analyses on sleep efficiency (SE), total sleep time (TST), daytime activity ratio (DAR), and hourly activity counts among critically ill MV adults from 9 ICUs across 2 hospitals.

METHODS

A secondary analysis was undertaken from our parent National Institutes of Health-funded randomized controlled trial (NIH R01 NR016702). Subjects included 31 critically ill patients from multiple ICUs. Wrist actigraphy estimated SE and TST. Mean DAR, an indicator of altered sleep-wake cycles, was calculated. Continuous 24-hour activity counts over 5 consecutive days were summarized. Descriptive analyses were used.

RESULTS

A total of 31 subjects with complete actigraphy data were included. Mean age was 59.6 (SD, 17.3) years; 41.9% were male; 83.9% were White, and 67.7% were Hispanic/Latino; and the mean APACHE III (Acute Physiology and Chronic Health Evaluation III) severity of illness score was 74.5 (SD, 25.5). The mean nighttime SE and TST over the 5-day ICU period were 83.1% (SD, 16.14%) and 6.6 (SD, 1.3) hours, respectively. The mean DAR over the 5-day ICU period was 66.5% (SD, 19.2%). The DAR surpassed 80% on only 17.5% of subject days. The majority of subjects' activity level was low, falling below 1000 activity counts per hour.

CONCLUSION

Our study revealed poor rest-activity cycle consolidation among critically ill MV patients during the early ICU period. Future interventional studies should promote quality sleep at nighttime and promote mobilization during the daytime.

Validity of actigraphy for nighttime sleep monitoring in hospitalized patients with traumatic injuries

STUDY OBJECTIVES

Sleep-wake disturbances are frequent among patients hospitalized for traumatic injuries but remain poorly documented because of the lack of tools validated for hospitalized patients. This study aimed to validate actigraphy for nighttime sleep monitoring of hospitalized patients with severe traumatic injuries, using ambulatory polysomnography (PSG).

METHODS

We tested 17 patients (30.4 ± 14.7 years, 16.6 ± 8.2 days postinjury) who had severe orthopedic injuries and/or spinal cord injury, with or without traumatic brain injury. When medically stable, patients wore an actigraph on a nonparalyzed arm and underwent ambulatory PSG at the bedside. Data were converted to 1-minute epochs. The following parameters were calculated for the nighttime period: total sleep time, total wake time, sleep efficiency, and number of awakenings. Epoch-by-epoch concordance between actigraphy and PSG was analyzed to derive sensitivity, specificity, and accuracy. PSG sleep parameters were compared to those obtained from four actigraphy scoring algorithms by Bland-Altman plots.

RESULTS

Sensitivity to detect sleep was ≥ 92% and accuracy was > 85% for all four actigraphy algorithms used, whereas specificity varied from 48% to 60%. The low-activity wake threshold (20 activity counts per epoch) was most closely associated with PSG on all sleep parameters. This scoring algorithm also had the highest specificity (59.9%) and strong sensitivity (92.8%).

CONCLUSIONS

Actigraphy is valid for monitoring nighttime sleep and wakefulness in patients hospitalized with traumatic injuries, with sensitivity, specificity and accuracy comparable to actigraphic recordings in healthy individuals. A scoring algorithm using a low wake threshold is best suited for this population and setting.