Pupillary instability reflects alterations in autonomic nervous system activity and has been shown to reflect change in alertness. However, the extent to which it can predict subsequent performance impairment and alertness failure is not clear. Eighteen healthy young adults (group age = 21.44 ± 3.24 years, 10 men) underwent 40 hr of continuous wakefulness, completing an 11-min Pupillographic Sleepiness Test (PST), the Karolinska Sleepiness Scale and a 10-min Psychomotor Vigilance Task (PVT) every 2 hr. Waking electroencephalography was recorded continuously and scored for microsleeps and slow eye movements (SEMs) during PVTs. Pupillary instability was sensitive to time awake, significantly increasing after 18 hr of wakefulness. The time course of impairment was almost identical to PVT lapses, microsleeps and SEMs. Receiver operating characteristic curve analysis demonstrated reasonable sensitivity and specificity of pupillary instability in correctly classifying PVT lapses, microsleeps and SEMs above individual baseline thresholds (all AUC values >0.78, p < 0.0001). Preliminary cut-off scores ranging from 10 to 11.5 mm/min for varying impairment thresholds are proposed for young adults. If reproducible in field settings, the PST may be a strong candidate as a fitness for duty/fitness to drive tool for detecting drowsiness-related impairment.
The pupillographic sleepiness test (PST) is an accurate predictor of alertness failure and performance impairment across sleep deprivation. At 11 min in duration, the task is considered too long to be used in occupational or roadside settings. We therefore investigated the predictive capacity of the PST at seven shortened test durations. Eighteen healthy young adults (aged 21.4 ± 3.2 years, 10 men) underwent 40 h of continuous wakefulness, completing an 11-min PST and a 10-min psychomotor vigilance task (PVT) every 2 h. Waking electroencephalography was recorded and scored for microsleeps during PVTs. The PST was divided into eight equal 82-s blocks and the predictive capacity of the pupillary unrest index (PUI) calculated at descending PST durations by systematically removing blocks. PUI increased significantly with time awake for all test durations (p < .0001), with a similar amplitude of PUI observed for test durations of 5.5 min and longer. While all test durations accurately predicted PVT impairment (AUC: 0.72-0.86, p < .001) and microsleep (AUC: 0.74-0.84, p < .0001), 5.5 min was the shortest duration where accuracy remained high across level and type of impairment (AUC: 0.79-0.86). For the 5.5-min duration, the positive predictive value (PPV) and negative predictive value (NPV) were on average 50.1% and 89.4%, respectively, and were comparable to the full 11min task (PPV: 49.2%; NPV: 91%). The PST can be shortened to 5.5 min without compromising accuracy in detecting performance impairment or physiological drowsiness. The PST is an ideal candidate for fitness-for-duty or fitness-to-drive testing, and future studies should examine its predictive capacity, at shorter durations, against operationally relevant outcomes.
Introduction: Circadian misalignment (e.g., shift work) is associated with worsened mood and mood has been shown to have a circadian rhythm. Notably, rhythmicity has been shown for feelings associated with reward-related motivation (positive affect) but not threat-related motivation (negative affect). We tested whether or not there exists a circadian rhythm in mood as assessed by the complete Positive and Negative Affect Scales (PANAS) and a questionnaire with validity in both psychiatric and normative populations. Methods: 15 participants without chronic medical or psychiatric illnesses were studied (aged 41-63 years; 9 females). Following 1-3 weeks of a regular sleep/wake schedule participants underwent a laboratory forced desynchrony protocol that distributed all scheduled sleep/wake behaviors evenly across the circadian cycle (achieved by scheduling 10 identical, recurrent 5 h 20 min 'days' in dim light thereby desynchronizing the circadian and behavioral cycles). POMS-B and PANAS were completed ~30 min. after waking. Scores were converted to z-scores and analyzed by cosinor analysis. Circadian phase at each mood assessment was determined relative to the salivary dim light melatonin onset (DLMO, 3 pg/ml threshold). Results: Both POMS-B mood score and PANAS positive affect items exhibited robust circadian rhythms (both p <0.001) with the worst mood and lowest positive affect occurring during the biological night (~6 hours after the DLMO or ~2:45 am) and the best mood and greatest positive affect at the end of the biological day (~2 hours before the DLMO). Negative affect mirrored positive affect (p = 0.01) with a peak ~ 6 hours after the DLMO and minimum ~6 hours before the DLMO but with an amplitude that was 39% of the rhythm in positive affect. Conclusion: Mood has an endogenous circadian rhythm driven principally by positive affect but also influenced by negative affect. Normative and clinical assessments of mood should take these rhythms into account. These rhythms may underlie the association between circadian misalignment and mood disorders and differences in rhythmicity of positive and negative affect might contribute to mood disorder risk. Support (If Any): R01 HL125893 (to SAS), NCC 9-58 and F32HL131308 (to SST) and UL1TR000128 (to Oregon Clinical & Translational Research Institute).
Introduction
Circadian rest-activity rhythms (RARs) disruption is common during chemotherapy for breast cancer, but little is known regarding its association with sleep and daytime functioning. In this study, we evaluated whether objectively-assessed RARs prospectively predict self-reported insomnia and fatigue symptoms, daytime sleep-related impairment, and sleep disturbance.
Methods
This is a secondary analysis of a trial. Participants (N=101) were randomized to cognitive behavioural plus light therapy or relaxation audios. Participants wore an actigraph continuously throughout the 6-week intervention. RAR indices (interdaily stability, intradaily variability, relative amplitude, least active 5h period [L5], most active 10h period [M10]) were calculated based on two weeks (4 & 5). Self-reported outcomes were assessed at weeks 3 and 6. Self-reported outcomes at week 6 were predicted by RAR indices controlling for self-reported outcomes at week 3 and intervention condition.
Results
Lower L5 predicted lower self-reported insomnia and fatigue symptoms, sleep-related impairment, and sleep disturbance (all p<.05). With the exception of insomnia symptoms (p>.05), higher inter-daily stability predicted lower symptoms of fatigue, sleep-related impairment and sleep disturbance (all p<.05). Similarly, excluding sleep disturbance (p>.05), higher relative amplitude predicted fewer endorsed symptoms on self-reported measures (all p<.01). Neither M10 nor intradaily variability predicted self-reported outcomes (all p>.05).
Discussion
RAR disruption demonstrated the most reliable association with daytime sleep-related complaints. The entrainment of a robust diurnal rhythm may reflect a novel intervention target. Direct intervention on distinct RAR characteristics may yield secondary gains on several self-reported sleep-related outcomes, particularly those related to daytime functioning.
Trial Registration
ACTRN12618001255279
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