0238 Effects of Blue-Enriched White Light and an Afternoon Nap on Alertness and Mood During a Simulated Long-Haul Flight

Abstract Introduction Cognitive functioning and mood are important determinants of a passenger’s flight experience. We hypothesized that ocular exposure to blue-enriched white light (BEWL) would improve cognition and mood in partially sleep-deprived passengers during a simulated long-haul business class flight. Daytime functioning was measured before and after an afternoon nap to test for effects of BEWL under high and low levels of homeostatic sleep pressure. Methods In a within-participant study, 51 adults (30 women; median age=23y) underwent 2 simulated long-haul flights (10:00-19:00) in a physical business class cabin simulator after a night of short sleep (5h). Participants were exposed to typical white light (control) or BEWL (intervention) matched for photopic illuminance for 2h before and after a scheduled nap in darkness (14:30-16:30). The melanopic equivalent daylight illuminance was 2-fold higher in the intervention versus the control at a given seat location (range=42-100lx versus 18-45lx). Self-rated alertness, reaction times, and positive affect were measured during baseline, pre-nap, and post-nap sessions. Two-way repeated measures ANOVA was used to test for effects of study visit (control, intervention) and session (baseline, pre-nap, post-nap) on behavioral outcomes. Results Effects of BEWL on alertness, reaction times, and positive affect did not differ relative to the control (interaction effect, P>0.11; main effect of study visit, P>0.41 for each comparison). However, there was a strong main effect of session (P≤0.001 for each comparison) where daytime functioning was better after the nap compared with either the baseline or pre-nap sessions. Pairwise comparisons showed that BEWL was associated with negligible effects relative to typical white light (Cohen’s d, range=0.00-0.20, P>0.16), whereas large effect sizes were observed for post-nap versus pre-nap behavior (Cohen’s d, range=0.70-2.14, P< 0.001). Conclusion BEWL did not boost daytime performance or mood using light levels that are typical of an airline cabin environment. By comparison, there were marked improvements in alertness, reaction times, and positive affect after an afternoon nap. These results suggest that sleep is more effective than BEWL at preventing deterioration in cognition and mood in partially sleep deprived passengers. Support (if any) The work was supported by National Research Foundation, Singapore and A*STAR (IAF-ICP I2001E0059) under the SIA-NUS Digital Aviation Corporate Laboratory.