Abstract Introduction Short-haul airline operations often require pilots to operate irregular schedules that encroach on the biological night. These schedules can impact sleep, and in turn, alertness, fatigue, and cognitive performance, which introduces a potential safety risk. There are many regulatory limits and industry practices that have been established to mitigate such impairments, but few studies have examined the impact of such schedules. Therefore, we aimed to evaluate the impact of circadian disruption on these outcomes during short-haul operations. Methods Participants included commercial passenger operations pilots from four US airlines. Data were collected 1-3 days before and after two trip types: one involving circadian disruption (i.e., one or more duties encroaching on 0000 and 0659) and one without circadian disruption (i.e., all duties scheduled between 0700 and 2359). Data included continuous actigraphy and daily sleep logs. Participants completed a five-minute Psychomotor Vigilance Task (PVT), Karolinska Sleepiness Scale (KSS), and Samn-Perelli fatigue scale (SP) 3x/day on days off; and after waking, pre-duty, at top-of-descent for each flight, post-duty, and before bed on duty days. Data were collected using the NASA PVT+ application on an iPod. We used RStudio (Version 2023.6.1.524) to compare outcomes with mixed-effects models, adjusted for multiple comparisons using the Benjamini-Hochberg procedure. Results In all, 159 participants provided valid data across 1,921 flights over 2,406 days. We found small but significant differences between circadian disrupted and non-disrupted trips with greater sleepiness (KSS: 4.77 □ 2.16 vs. 4.43 □ 2.11, p .001, d = 0.20), greater fatigue (SP: 3.64 □ 1.38 vs. 3.37 □ 1.34, p .001, d = 0.25), slower PVT speed (1000/reaction time; 3.86 □ 0.63 vs. 3.94 □ 0.61, p .001, d = -0.27) and less total sleep time (6.30 □ 1.69 h vs. 6.78 □ 1.28 h, p .001, d = -0.29). Conclusion Our findings suggest that there is a small but significant cost to working during the biological night that remains even when prescriptive limitations and existing airline mitigations are in place. Support (if any) This study was funded by an interagency agreement between the Federal Aviation Administration and the NASA System-wide Safety Program.
Flynn-Evans et al. (Fri,) studied this question.