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BACKGROUND: Many workers routinely transition between day and night shifts--including pilots, where night flights are commonly considered more stressful. The physiological toll from this transition is not fully understood, though fatigue is a factor in many aviation accidents. This research investigated the changes in physiological markers of stress and cognitive performance as F-22 pilots transitioned from day flying to night flying. METHODS: There were 17 fully-qualified F-22 pilots who took part in a 2-wk data collection using salivary swabs, wrist-worn activity monitors, the National Aeronautics and Space Administration-Task Load Index (NASA-TLX) inventory, and a go/no-go (GNG) test. RESULTS: No differences were found in comparing day and night flying on the GNG reaction time/accuracy, NASA-TLX scores, or sleep quantity. Cortisol levels were significantly higher than civilian levels in all experimental conditions and control days. Participants had higher than predicted cortisol levels postflight in the day-flying condition and lower than predicted cortisol levels postflight in the night-flying condition, relative to levels from control day patterns. We also found smaller changes in cortisol (pre- to postflight) in the day-flying condition for those with more F-22 experience. Finally, we found a negative correlation between Perceived Stress Scale scores and age of pilots (r 5 20.72). DISCUSSION: We hypothesized that the night-flying environment would be more stressful, but our results disputed this claim. Our results suggest day flying elicits more of a stress response; however, a larger sample size is required to verify results. Preliminary findings of potential stress adaptation may suggest stress adaptation in the F-22 community needs further investigation. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Environmental motion can affect shipboard sleep of crewmembers. Slamming and similar harsh motion may interfere with sleep, whereas mild motion and sopite syndrome may enhance sleep. If sleep needs vary by sea condition, this factor should be considered when assessing human performance at sea. The goal of this study was to assess sleep duration in different sea conditions. METHODS: Crewmembers (N = 52) from a U.S. Navy vessel participated in the study while performing their normal daily schedule of duties. Sleep was assessed with wrist-worn actigraphy. Motion sickness and sopite syndrome were assessed using standardized questionnaires. RESULTS: In rough sea conditions, crewmembers experienced increased severity of motion sickness and sopite syndrome compared to their ratings during calmer sea conditions. Crewmembers slept significantly longer during sea state 5-6 compared to sleep on days with sea state 4 (25% increase) and sea state 3-4 (30% increase). Specifically, daily sleep increased from 6.97 ± 1.24 h in sea state 3-4, to 7.23 ± 1.65 h in sea state 4, to 9.04 ± 2.90 h in sea state 5-6. DISCUSSION: Although the duration of sleep in rough seas increased significantly compared to calmer sea conditions, causal factors are inconclusive. Accumulated sleep debt, motion-induced fatigue, and sopite syndrome all may have contributed, but results suggest that motion sickness and sopite syndrome were the predominant stressors. If sleep needs increase in severe motion environments, this factor should be taken into account when developing daily activity schedules or when modeling manning requirements on modern ships. [ABSTRACT FROM AUTHOR]