The moderating role of conscientiousness in the temporal association of stress on sleep.

Personality traits have been associated with sleep problems and stress experience. However, their impact on objective sleep and the temporal relationship of stress on sleep has remained elusive. This study examined whether daytime stress predicts sleep the following night, and the moderating role of neuroticism and conscientiousness in this relationship. To introduce stress variability in natural daily stressors, we measured college students (N = 92) during exams (e.g. high academic stress) and at the start of new course period (e.g. low academic stress). Both objective (actigraphy) and subjective sleep, and daily self-reported stress, were measured for 14 days and personality traits once. Reported daily stress was significantly higher in the exam period compared with baseline, suggesting that our natural manipulation did indeed result in variation in stress levels. Intra-individual daily variations in stress were not associated with the following night's sleep timing, duration or fragmentation, implying that more stress during the day did not affect sleep the following night. Higher levels of neuroticism were associated with poorer daily subjective sleep quality and higher stress levels over the complete period. Neuroticism did not moderate the temporal association of stress on sleep. Conscientiousness moderated the association between intra-individual stress and sleep fragmentation, and intra-individual stress and wake-up time. This implied that highly conscientious participants experienced less sleep fragmentation and woke-up earlier after more stressful days. These results suggest an interconnected relationship among stress, sleep and personality. Focusing on one aspect, like handling stress or enhancing sleep quality, might yield positive effects on the rest.

The relation between insomnia and depression in the subacute phase after stroke.

Prevalence rates for both depression and insomnia the first year after stroke are around 30%, significantly impacting the prospects of recovery, rehabilitation, and quality of life. Furthermore, the risk of insomnia and depression becoming chronic is high in the subacute phase post-stroke. This cross-sectional observational study investigated whether insomnia and depression are related in the subacute phase post-stroke, using validated instruments. Sixty-six outpatient stroke survivors participated. Depression was measured using the depression subscale of the Hospital Anxiety and Depression Scale (HADS-D) and insomnia severity with the Insomnia Severity Index (ISI). A multiple linear regression analysis was used to examine the association between the dependent variable post-stroke depression and the independent variables insomnia and pre-stroke depression treatment. Results showed that insomnia (ß = 0.48, t = 4.40, p < 0.001) and pre-stroke depression treatment (ß = 0.24, t = 2.28, p = 0.026) were both significant predictors of depression. Participants with more insomnia complaints and participants with pre-stroke depression treatment had more depression symptoms post-stroke. Therefore, it is important to be alert in the subacute phase post-stroke of both, insomnia and depression complaints.

Functional connectivity correlates of attentional networks in insomnia disorder: A pilot study.

Insomnia disorder has been associated with poor executive functioning. Functional imaging studies of executive functioning in insomnia are scarce and inconclusive. Because the Attentional Network Test relies on well-defined cortical networks and sensitively distinguishes different aspects of executive function, it might reveal brain functional alterations in relatively small samples of patients. The current pilot study assessed functional connectivity during the Attentional Network Test performed using magnetic resonance imaging in 12 participants with insomnia and 13 self-defined good sleepers. ANCOVAs were used to evaluate group differences in performance and functional connectivity in the regions of interest representing the attentional networks (i.e. alerting, orienting and executive control) at p < 0.05, uncorrected. During the orienting part, participants with insomnia showed weaker connectivity of the precentral gyrus with the superior parietal lobe (false discovery rate-corrected), while they showed stronger connectivity between premotor and visual regions. Individual differences in connectivity between premotor and visual regions correlated inversely with reaction time. Reaction times suggested more efficient executive control in participants with insomnia compared with good sleepers. During the executive control part, participants with insomnia showed stronger connectivity of thalamic parts of the arousal circuit with the middle frontal and the occipital gyri. Conversely, connectivity between the inferior and superior frontal gyri was weaker. Participants with insomnia seem to recruit more cortical resources in visuo-motor regions to orient attention than good sleepers do, and seem to have enhanced executive control that relates to stronger connectivity of arousal-related thalamic areas. This latter result should be treated with caution and requires confirmation.

The bidirectional relationship between sleep and physical activity following traumatic brain injury.

Sleep and physical activity are both modifiable behavioural factors that are associated with better health and are potentially related. Following traumatic brain injury, damage to the brain caused by an external force, sleep disturbances are common. Exploring bidirectional relationships between sleep and physical activity might provide insight into whether increasing physical activity could decrease these sleep disturbances. The current study, therefore, examined inter- and intra-individual temporal associations between sleep and daytime physical activity in 64 people with traumatic brain injury reporting sleep problems or fatigue (47 males; mean age, 40 years). Sleep and physical activity were measured using actigraphy with corroborating sleep diaries over 14 consecutive days. Multilevel models were used to examine inter- and intra-individual associations between physical activity and sleep. Inter-individual variations showed that earlier bedtimes, earlier wake-up times and lower sleep efficiency were associated with more physical activity. Intra-individual temporal variations showed no significant association of daytime physical activity with sleep duration or continuity. However, shorter sleep time and less wake after sleep onset than usual were associated with more time spent in light-intensity activity the next day. Therefore, sleep may have more of an influence on physical activity than physical activity has on sleep in people with traumatic brain injury. In conclusion, the results do not confirm a potential beneficial effect of physical activity on sleep but suggest that improving sleep quality might be relevant to support of a physically active lifestyle in people with traumatic brain injury. Further research is necessary to confirm these results.

Increased hippocampal-prefrontal functional connectivity in insomnia.

Insomnia Disorder (ID) is the second-most common mental disorder and has a far-reaching impact on daytime functioning. A meta-analysis indicates that, of all cognitive domains, declarative memory involving the hippocampus is most affected in insomnia. Hippocampal functioning has consistently been shown to be sensitive to experimental sleep deprivation. Insomnia however differs from sleep deprivation in many aspects, and findings on hippocampal structure and function have been equivocal. The present study used both structural and resting-state functional Magnetic Resonance Imaging in a larger sample than previously reported to evaluate hippocampal volume and functional connectivity in ID. Included were 65 ID patients (mean age = 48.3 y ±â€¯14.0, 17 males) and 65 good sleepers (mean age = 44.1 y ±â€¯15.2, 23 males). Insomnia severity was assessed with the Insomnia Severity Index (ISI), subjective sleep with the Consensus Sleep Diary (CSD) and objective sleep by two nights of polysomnography (PSG). Seed-based analysis showed a significantly stronger connectivity of the bilateral hippocampus with the left middle frontal gyrus in ID than in controls (p = .035, cluster based correction for multiple comparisons). Further analyses across all participants moreover showed that individual differences in the strength of this connectivity were associated with insomnia severity (ISI, r = 0.371, p = 9.3e-5) and with subjective sleep quality (CSD sleep efficiency, r = -0.307, p = .009) (all p FDR-corrected). Hippocampal volume did not differ between ID and controls. The findings indicate more severe insomnia and worse sleep quality in people with a stronger functional connectivity between the bilateral hippocampus and the left middle frontal gyrus, part of a circuit that characteristically activates with maladaptive rumination and deactivates with sleep.

Post-illumination pupil response after blue light: Reliability of optimized melanopsin-based phototransduction assessment.

Melanopsin-containing retinal ganglion cells have recently been shown highly relevant to the non-image forming effects of light, through their direct projections on brain circuits that regulate alertness, mood and circadian rhythms. A quantitative assessment of functionality of the melanopsin-signaling pathway could be highly relevant in order to mechanistically understand individual differences in the effects of light on these regulatory systems. We here propose and validate a reliable quantification of the melanopsin-dependent Post-Illumination Pupil Response (PIPR) after blue light, and evaluated its sensitivity to dark adaptation, time of day, body posture, and light exposure history. Pupil diameter of the left eye was continuously measured during a series of light exposures to the right eye, of which the pupil was dilated using tropicamide 0.5%. The light exposure paradigm consisted of the following five consecutive blocks of five minutes: baseline dark; monochromatic red light (peak wavelength: 630 nm, luminance: 375 cd/m(2)) to maximize the effect of subsequent blue light; dark; monochromatic blue light (peak wavelength: 470 nm, luminance: 375 cd/m(2)); and post-blue dark. PIPR was quantified as the difference between baseline dark pupil diameter and post-blue dark pupil diameter (PIPR-mm). In addition, a relative PIPR was calculated by dividing PIPR by baseline pupil diameter (PIPR-%). In total 54 PIPR assessments were obtained in 25 healthy young adults (10 males, mean age ± SD: 26.9 ± 4.0 yr). From repeated measurements on two consecutive days in 15 of the 25 participants (6 males, mean age ± SD: 27.8 ± 4.3 yrs) test-retest reliability of both PIPR outcome parameters was calculated. In the presence of considerable between-subject differences, both outcome parameters had very high test-retest reliability: Cronbach's α > 0.90 and Intraclass Correlation Coefficient > 0.85. In 12 of the 25 participants (6 males, mean age ± SD: 26.5 ± 3.6 yr) we examined the potential confounding effects of dark adaptation, time of the day (morning vs. afternoon), body posture (upright vs. supine position), and 24-h environmental light history on the PIPR assessment. Mixed effect regression models were used to analyze these possible confounders. A supine position caused larger PIPR-mm (ß = 0.29 mm, SE = 0.10, p = 0.01) and PIPR-% (ß = 4.34%, SE = 1.69, p = 0.02), which was due to an increase in baseline dark pupil diameter; this finding is of relevance for studies requiring a supine posture, as in functional Magnetic Resonance Imaging, constant routine protocols, and bed-ridden patients. There were no effects of dark adaptation, time of day, and light history. In conclusion, the presented method provides a reliable and robust assessment of the PIPR to allow for studies on individual differences in melanopsin-based phototransduction and effects of interventions.

Mental effort and recovery from task-induced fatigue in people with traumatic brain injury.

PURPOSE: This exploratory case-controlled study examined whether the same amount of effort leads to similar feelings of fatigue and whether feelings of fatigue decline at the same rate in people with traumatic brain injury (pwTBI) compared to controls. METHODS: Twenty pwTBI and 20 healthy controls (HC) completed an adaptive n-back task to induce fatigue and reported mental effort upon task completion and state-fatigue pre-task and several times during 30-minutes rest-period post-task. Task difficulty adapted to performance allowing both groups to invest substantial amounts of mental effort. RESULTS: Fatigue and effort levels were higher in pwTBI compared to controls. Multiple linear regression analyses showed that effort was positively related to post-task fatigue and this relationship did not differ between groups. Pre-task fatigue was the only predictor of post-task fatigue. Multilevel models showed no significant difference in decline of fatigue over the rest-period between groups. CONCLUSIONS: Excessive feelings of fatigue following TBI could not be explained by a higher vulnerability to the fatigue-inducing effects of mental effort needed to perform a specific task. In pwTBI pre-task fatigue levels might be more related to the complex demands of everyday life. Future studies should investigate recovery of fatigue and applications of this knowledge to rehabilitation interventions.Implications for rehabilitationPeople with TBI experience long-term fatigue as one of the most frequent and disabling symptoms and this long-term fatigue is a risk factor for development of secondary psychiatric symptoms such as depression or anxiety.Since people with TBI did not show a higher vulnerability to the fatigue-inducing effects of mental effort, fatigue following TBI might be better explained by the complex demands of everyday life such as external (environment) and internal (emotions) factors.Rehabilitation programs should be directed to this complex and highly individual interplay of fatigue in relation to other factors.

Measuring fatigue following acquired brain injury: A validation study of the Psychomotor Vigilance Test.

OBJECTIVE: To evaluate the construct validity of Psychomotor Vigilance Test performance for measuring fatigue in people with acquired brain injury. DESIGN: Observational cross-sectional study. PARTICIPANTS: Fifty-four people with acquired brain injury and 61 healthy controls. METHODS: Participants performed the Psychomotor Vigilance Test and reported momentary fatigue before and after this test and general fatigue. Associations between performance and fatigue in patients were tested by correlational and hierarchical multiple linear regression analyses, controlling for sleep quality, daytime sleepiness, and mood. RESULTS: Patients performed worse on the test compared with controls. Within the patient group, worse test performance was associated with increases in momentary post-test fatigue and general fatigue, indicating convergent validity, but also with daytime sleepiness, and mood complaints, indicating a lack of divergent validity. When controlling for sleepiness and mood, the association between performance and general fatigue was no longer significant, whereas the association between performance and post-test fatigue remained. CONCLUSION: Performance on the Psychomotor Vigilance Test cannot be used as a specific measure for fatigue, but it appears to be a more general measure of severity of symptoms including fatigue, mood, and sleepiness. Therefore, the Psychomotor Vigilance Test may be a useful measure to examine the effects of interventions aimed at reducing these symptoms.

Unraveling the Biopsychosocial Factors of Fatigue and Sleep Problems After Traumatic Brain Injury: Protocol for a Multicenter Longitudinal Cohort Study.

BACKGROUND: Fatigue and sleep problems are common after a traumatic brain injury (TBI) and are experienced as highly distressing symptoms, playing a significant role in the recovery trajectory, and they can drastically impact the quality of life and societal participation of the patient and their family and friends. However, the etiology and development of these symptoms are still uncertain. OBJECTIVE: The aim of this study is to examine the development of fatigue and sleep problems following moderate to severe TBI and to explore the changes in underlying biological (pain, brain damage), psychological (emotional state), and social (support family, participation) factors across time. METHODS: This study is a longitudinal multicenter observational cohort study with 4 measurement points (3, 6, 12, and 18 months postinjury) including subjective questionnaires and cognitive tasks, preceded by 7 nights of actigraphy combined with a sleep diary. Recruitment of 137 moderate to severe TBI patients presenting at emergency and neurology departments or rehabilitation centers across the Netherlands is anticipated. The evolution of fatigue and sleep problems following TBI and their association with possible underlying biological (pain, brain damage), psychological (emotional state), and social (support family, participation) factors will be examined. RESULTS: Recruitment of participants for this longitudinal cohort study started in October 2017, and the enrollment of participants is ongoing. The first results are expected at the end of 2020. CONCLUSIONS: To the authors' knowledge, this is the first study that examines the development of both post-TBI fatigue and sleep longitudinally within a biopsychosocial model in moderate to severe TBI using both subjective and objective measures. Identification of modifiable factors such as mood and psychosocial stressors may give direction to the development of interventions for fatigue and sleep problems post-TBI. TRIAL REGISTRATION: Netherlands Trial Register NTR7162; http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=7162 (Archived by WebCite at http://www.webcitation.org/6z3mvNLuy). INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR1-10.2196/11295.

Individual Differences in Sleep Timing Relate to Melanopsin-Based Phototransduction in Healthy Adolescents and Young Adults.

STUDY OBJECTIVES: Individual differences in sleep timing have been widely recognized and are of particular relevance in adolescents and young adults who often show mild to severely delayed sleep. The biological mechanisms underlying the between-subject variance remain to be determined. Recent human genetics studies showed an association between sleep timing and melanopsin gene variation, but support for functional effects on downstream pathways and behavior was not demonstrated before. We therefore investigated the association between the autonomic (i.e., pupil diameter) and behavioral (i.e., sleep timing) readouts of two different downstream brain areas, both affected by the same melanopsin-dependent retinal phototransduction: the olivary pretectal nucleus (OPN) and the suprachiasmatic nucleus (SCN). METHODS: Our study population included 71 healthy individuals within an age range with known vulnerability to a delayed sleep phase (16.8-35.7 y, 37 males, 34 females). Pupillometry was performed to estimate functionality of the intrinsic melanopsin-signaling circuitry based on the OPN-mediated post-illumination pupil response (PIPR) to blue light. Sleep timing was quantified by estimating the SCN-mediated mid-sleep timing in three different ways in parallel: using a chronotype questionnaire, a sleep diary, and actigraphy. RESULTS: All three measures consistently showed that those individuals with a later mid-sleep timing had a more pronounced PIPR (0.03 < P < 0.05), indicating a stronger blue-light responsiveness of the intrinsic melanopsin-based phototransduction circuitry. CONCLUSIONS: Trait-like individual differences in the melanopsin phototransduction circuitry contribute to individual differences in sleep timing. Blue light-sensitive young individuals are more prone to delayed sleep.

Individual Differences in the Post-Illumination Pupil Response to Blue Light: Assessment without Mydriatics.

Melanopsin-containing retinal ganglion cells play an important role in the non-image forming effects of light, through their direct projections on brain circuits involved in circadian rhythms, mood and alertness. Individual differences in the functionality of the melanopsin-signaling circuitry can be reliably quantified using the maximum post-illumination pupil response (PIPR) after blue light. Previous protocols for acquiring PIPR relied on the use of mydriatics to dilate the light-exposed eye. However, pharmacological pupil dilation is uncomfortable for the participants and requires ophthalmological expertise. Hence, we here investigated whether an individual's maximum PIPR can be validly obtained in a protocol that does not use mydriatics but rather increases the intensity of the light stimulus. In 18 participants (5 males, mean age ± SD: 34.6 ± 13.6 years) we evaluated the PIPR after exposure to intensified blue light (550 µW/cm²) provided to an undilated dynamic pupil. The test-retest reliability of the primary PIPR outcome parameter was very high, both between day-to-day assessments (Intraclass Correlation Coefficient (ICC) = 0.85), as well as between winter and summer assessments (ICC = 0.83). Compared to the PIPR obtained with the use of mydriatics and 160 µW/cm² blue light exposure, the method with intensified light without mydriatics showed almost zero bias according to Bland-Altman plots and had moderate to strong reliability (ICC = 0.67). In conclusion, for PIPR assessments, increasing the light intensity is a feasible and reliable alternative to pupil dilation to relieve the participant's burden and to allow for performance outside the ophthalmological clinic.

Personality as a risk factor for illicit opioid use and a protective factor for illicit opioid dependence.

BACKGROUND: Most studies investigating the role of personality as a risk factor for the development of opioid dependence compare dependent opioid users with healthy controls who never used heroin. In order to understand the potential protective role of personality, it is crucial to compare illicit opioid users who never became dependent with dependent opioid users. AIMS: This study aims to examine the role of personality as a risk factor for opioid use and as a protective factor for the development of opioid dependence. METHODS: Comparing personality factors between three groups: (1) 161 never-dependent illicit opioid users who have been using illicit opioids but never became opioid dependent; (2) 402 dependent opioid users in methadone maintenance treatment or heroin-assisted treatment; and (3) 135 healthy controls who never used heroin. Personality was assessed with a short version of Cloninger's Temperament and Character Inventory. RESULTS: Never-dependent opioid users reported more Novelty Seeking and Harm Avoidance and less Self-Directedness and Cooperativeness than healthy controls and more Reward Dependence and Self-Directedness, and less Harm Avoidance than dependent opioid users. Furthermore, never-dependent opioid users reported more Self-Transcendence than both dependent opioid users and healthy controls. CONCLUSIONS: Never-dependent opioid users may have started to use opioids partly due to their tendency to seek novel and/or spiritual experiences (high Novelty Seeking, high Self-Transcendence) and their tendency to avoid aversive stimuli (high Harm Avoidance), whereas they may have been protected against the development of dependence by their need for social approval (high Reward Dependence) and their self-efficacy (high Self-Directedness).