0005 A circadian-informed lighting intervention markedly improves vigilance in a simulated night shift setting

Abstract

Abstract Introduction Due to misalignment between circadian timing and the work/rest schedule, cognitive performance during night shift-work is often poor. This study tested a circadian-informed lighting strategy designed to improve on-shift cognitive performance through alerting effects, faster circadian adjustment to the shift-work schedule and promoting more sleep off-shift, compared to standard lighting. Methods A randomised controlled, within-subjects, counter-balanced cross-over study was performed to examine circadian-informed versus standard lighting on cognitive performance during a simulated 8-day night shift-work schedule. Nineteen healthy sleepers (12 males/7 females, mean±SD aged 28.7±10.4 years) underwent two separate 8-day experimental conditions in the sleep laboratory. The standard lighting condition mimicked current lighting on submarines (largely dim, blue-depleted light), while the circadian-informed lighting administered bright, blue-enriched and dim, blue-depleted lighting at times estimated to facilitate rapid circadian delay. After an adaptation sleep opportunity from 22:00 – 07:00 (day 1), participants remained awake for 27 hours to transition to sleeping during the day (10:00 - 19:00) and undertaking simulated night shift-work (00:00 - 08:00) at night on days 3-7. The primary performance outcome was the number of lapses (>500ms responses) on the psychomotor vigilance task (PVT), administered six times across each simulated work shift. Median reaction time and other PVT outcomes were also compared between lighting conditions. Results There were significant day-by-condition interactions on PVT lapses, p< 0.05. The circadian-informed lighting intervention resulted in ~50% fewer lapses by the final day compared to standard lighting (mean±SD 7.4±5.0 vs. 15.6±6.1 lapses). Similar effects were observed across other PVT outcomes. Conclusion Circadian-informed lighting resulted in markedly better vigilance than standard lighting under simulated night shift-work conditions. These findings indicate the considerable potential for automated lighting interventions to improve performance and safety in shift-workers. Support (if any) This research is supported by the Commonwealth of Australia as represented by the Defence Science and Technology Group of the Department of Defence through the Research Network for Undersea Decision Superiority (research agreement number: 9334), with additional financial support from Flinders University and lighting provision support from REDARC.