0178 INDIVIDUALS SHOW DIFFERENTIAL VULNERABILITY IN NEUROBEHAVIORAL AND AFFECTIVE RESPONSES TO STRESS AND SLEEP LOSS IN NON-LABORATORY CONDITIONS

Abstract

Introduction: In highly-controlled laboratory studies, there are substantial individual differences (resilience and vulnerability) in neurobehavioral deficits from psychosocial stress and sleep loss. We determined whether highly-motivated subjects would show such individual differences in performance and affective responses to stress and sleep loss in non-laboratory, field-like conditions. Methods: 32 adults (35.1 ± 7.1y; 14 females) participated in a 14-day or 30-day mission in the NASA Human Exploration Research Analog facility at Johnson Space Center. Toward the end of the time in mission, crewmembers were part of a 5-day study consisting of 2 baseline nights (8h time in bed (TIB); 2300h-0700h), followed by 39h of total sleep deprivation (TSD) and 2 recovery nights (10h TIB: 2200h-0800h; 8h TIB: 2300h-0700h). The TSD day included a modified Trier Social Stress Test among other stressors. Compliance was verified by actigraphy. Crewmembers completed 11 neurobehavioral testing sessions during the 5-day study. The neurobehavioral sessions included tests measuring reaction time (the Psychomotor Vigilance Test [PVT]) and cognitive throughput (Digit Symbol Substitution Test [DSST]), and subjective scales measuring sleepiness (Karolinska Sleepiness Scale [KSS]), and fatigue, vigor and various aspects of mood (Profile of Mood States, Short Form [POMS-SF]). Paired t-tests compared performance and subjective ratings between baseline and TSD. Results: Crewmembers showed significant performance deficits (PVT, DSST), increased sleepiness and fatigue (KSS, POMSFatigue), and greater negative affect (POMS-Anger, POMSDepression and POMS-Total Mood Disturbance) during TSD compared to baseline (all p's<0.05). Notably, there were considerable individual differences in these responses to stress and sleep loss, as demonstrated by substantially larger standard deviations during TSD than at baseline. Conclusion: Highly-motivated subjects showed robust individual differences in performance, sleepiness, fatigue and affective responses to stress and sleep loss, even with limited testing assessments. Our results are remarkably similar to those observed in controlled laboratory studies, permitting generalization of differential vulnerability to other environments and populations.