Raw scores on subjective sleepiness, fatigue, and vigor metrics consistently define resilience and vulnerability to sleep loss

Abstract

Study Objectives Although trait-like individual differences in subjective responses to sleep restriction (SR) and total sleep deprivation (TSD) exist, reliable characterizations remain elusive. We comprehensively compared multiple methods for defining resilience and vulnerability by subjective metrics. Methods 41 adults participated in a 13-day experiment:2 baseline, 5 SR, 4 recovery, and one 36h TSD night. The Karolinska Sleepiness Scale (KSS) and the Profile of Mood States Fatigue (POMS-F) and Vigor (POMS-V) were administered every 2h. Three approaches (Raw Score [average SR score], Change from Baseline [average SR minus average baseline score], and Variance [intraindividual SR score variance]), and six thresholds (±1 standard deviation, and the highest/lowest scoring 12.5%, 20%, 25%, 33%, 50%) categorized Resilient/Vulnerable groups. Kendall’s tau-b correlations compared the group categorization’s concordance within and between KSS, POMS-F, and POMS-V scores. Bias-corrected and accelerated bootstrapped t-tests compared group scores. Results There were significant correlations between all approaches at all thresholds for POMS-F, between Raw Score and Change from Baseline approaches for KSS, and between Raw Score and Variance approaches for POMS-V. All Resilient groups defined by the Raw Score approach had significantly better scores throughout the study, notably including during baseline and recovery, whereas the two other approaches differed by measure, threshold, or day. Between-measure correlations varied in strength by measure, approach, or threshold. Conclusion Only the Raw Score approach consistently distinguished Resilient/Vulnerable groups at baseline, during sleep loss, and during recovery‒‒we recommend this approach as an effective method for subjective resilience/vulnerability categorization. All approaches created comparable categorizations for fatigue, some were comparable for sleepiness, and none were comparable for vigor. Fatigue and vigor captured resilience/vulnerability similarly to sleepiness but not each other.

Cortisol and C-Reactive Protein Vary During Sleep Loss and Recovery but Are Not Markers of Neurobehavioral Resilience

“…During sleep deprivation and psychological stress, the range of the Spearman relative rank correlations between the two objective performance measures (3-min PVT and DSST) was ρ = −0.579, p = 0.001, and the range between the objective performance measures and the KSS was ρ = −0.142-0.371, p = 0.036-0.439. The profiles of change in NTB performance and self-report scores with sleep loss and psychological stress are comparable to results obtained in laboratory studies (Dennis et al, 2017;Yamazaki and Goel, 2020;Brieva et al, 2021;Casale et al, 2021b;Yamazaki et al, 2021a,b).…”

“…Sleep-wake episodes were verified objectively by wrist actigraphy (Philips Respironics Healthcare, Bend, OR, United States). Actigraphic sleep data were analyzed as in our prior studies ( Dennis et al, 2017 ; Moreno-Villanueva et al, 2018 ; Yamazaki and Goel, 2020 ; Brieva et al, 2021 ; Casale et al, 2021b ; Yamazaki et al, 2021a ).…”

“…The KSS ( Åkerstedt and Gillberg, 1990 ) measures self-reported sleepiness. All tests are well-validated measures to examine sleep loss and they show stable, robust individual differences in healthy populations ( Dennis et al, 2017 ; Yamazaki and Goel, 2020 ; Brieva et al, 2021 ; Casale et al, 2021b ; Yamazaki et al, 2021a ), and were administered in the following order during all test bouts: DSST, KSS, 3-min PVT. As such, resilient and vulnerable individuals were determined by a median split on average values from the three NTB sessions during TSD ( Patanaik et al, 2015 ; Moreno-Villanueva et al, 2018 ; Caldwell et al, 2020 ) for 3-min PVT total lapses and errors, DSST performance, and KSS scores.…”

“…As such, resilient and vulnerable individuals were determined by a median split on average values from the three NTB sessions during TSD ( Patanaik et al, 2015 ; Moreno-Villanueva et al, 2018 ; Caldwell et al, 2020 ) for 3-min PVT total lapses and errors, DSST performance, and KSS scores. We dichotomized participants as such given that, for initial examination and categorization of novel biomarkers, it is more suitable and applicable to create resilient and vulnerable groups in healthy adult samples, as per convention in the field ( Chuah et al, 2009 ; Rocklage et al, 2009 ; Chee and Tan, 2010 ; Diekelmann et al, 2010 ; Patanaik et al, 2015 ; Yeo et al, 2015 ; Xu et al, 2016 ; Moreno-Villanueva et al, 2018 ; Caldwell et al, 2020 ; Salfi et al, 2020 ; Brieva et al, 2021 ; Casale et al, 2021b ; Yamazaki et al, 2021b ), especially given our sample size. Importantly, systematic examination of multiple approaches and thresholds for evaluating differential neurobehavioral vulnerability to sleep loss has demonstrated that median splits on averaged performance scores, rather than change from baseline or variance in scores, are consistent indicators of resilience and vulnerability during sleep deprived and well-rested periods ( Brieva et al, 2021 ; Casale et al, 2021b ; Yamazaki et al, 2021b ), thus further justifying our methods.…”

“…Chronic sleep deprivation is an important public health concern associated with many adverse health outcomes and clinical disorders such as anxiety, depression, immune dysfunction, Alzheimer’s disease, cardiovascular disease, obesity, cancer, and overall morbidity and mortality ( Ferrie et al, 2007 ; Gallicchio and Kalesan, 2009 ; Mullington et al, 2009 ; Phan and Malkani, 2019 ; Al-Rashed et al, 2021 ). Sleep deprivation is a potent stressor generally resulting in marked increases in physiological sleepiness (e.g., the Maintenance of Wakefulness Test and the Multiple Sleep Latency Test) and subjective sleepiness [e.g., the Karolinska Sleepiness Scale (KSS)] and significant deficits in cognitive performance ( Banks and Dinges, 2007 ; Goel et al, 2009 ; Casale et al, 2021a , b ; Yamazaki et al, 2021a , b ). However, a number of studies show there are robust and highly replicable phenotypic individual differences in response to repeated exposure to sleep deprivation: some individuals are resilient, and others are vulnerable to total sleep deprivation (TSD) and chronic sleep restriction (SR), both commonly experienced types of sleep loss ( Van Dongen et al, 2004 ; Goel et al, 2009 ; Dennis et al, 2017 ; Yamazaki and Goel, 2020 ).…”