0010 Impact of Blue-Enriched Light on Circadian Phase in Short-Haul Pilots with Early Start Times

Abstract Introduction Commercial airline pilots are often required to work early in the morning, before sunrise. These early starts often result in shortened sleep due to the need to go to bed and wake up early. Consequently, pilots may experience reduced alertness and performance while at work. Blue-enriched morning light exposure is an effective countermeasure for shifting circadian phase that could be useful in this population. Thus, we aimed to evaluate the effectiveness of blue-enriched light exposure to advance pilots’ circadian timing during a series of early start work shifts. Methods We recruited pilots at a short-haul airline to complete a within-subjects randomized, counterbalanced study involving two early-start work blocks lasting five days, preceded by a baseline period of five days of daytime flying followed by 2-4 days off. Participants were randomized to either a blue-enriched light or a control condition for approximately 30 minutes during pre-duty briefing. Circadian timing was measured at the end of each work block via 24-hour urine sampling. Samples were assayed for 6-sulphatoxymelatonin (aMT6s) concentration, and cosinor analysis was used to estimate peak aMT6s secretion. Results The final sample consisted of 12 males (Mean age: 38, SD = 9.50 years). In the baseline light condition, the mean acrophase time was 04:17 (SD = 01:41), range: 00:33 - 06:26 while under the baseline placebo condition, the mean acrophase time was 04:07 (SD = 01:37), range: 01:03 - 06:23. In the blue-enriched light condition the mean acrophase time was 02:22 (SD = 01:35), range: 23:42 - 04:08 while under the placebo condition the mean acrophase time was 02:41 (SD = 01:35), range: 00:04 - 05:06. Mixed effects regression analyses showed no significant differences in mean acrophase time between the light and placebo conditions (b = -0.55, SE = 0.29, p = .09, ω2 = 0.15, R2(Marginal) = .04, R2(Conditional) = .91). Conclusion Circadian phase varied according to work shift start time showing large inter-individual difference in both conditions. Future research will explore how such lighting countermeasures influence alertness, performance, and sleep. Support (if any) This study was funded by the NASA Airspace Operations and Safety Program.