0136 Bright Light Could Be an Alternative to the Caffeine for Improving Driving Performance in Chronically Sleep-Deprived Young Drivers

Introduction: Young drivers are over-involved in sleepiness-related crashes. Daytime and nighttime exposure to light might shift the human circadian phase and alertness. The alerting effects of bright light were compared with those of caffeine in young drivers. Methods: In a within-subjects study, 30 chronically sleep-deprived non-professional drivers (aged 18–24 years) completed two simulated daytime driving sessions per day across three consecutive days. Participants completed the first drive under a Baseline condition (non-caffeinated gum, 555 nm light, 0.3 µW/cm²), and the second drive under the randomized conditions of Light (500 nm, 230 µW/cm²), Caffeine (100 mg caffeinated gum) or the combination of Light and Caffeine. Using mixed-effects models, the alerting effects of these conditions on objective sleepiness (ECG beat-to-beat intervals), driving performance (lateral lane variability) and subjective sleepiness (scores on the Karolinska sleepiness scale; KSS) were examined. Results: Compared to the Baseline condition, lateral lane variability decreased under the Light (P=0.011), Caffeine (P=0.0001), and the combination of Light and Caffeine (P=0.046). Lateral lane variability was lower under Caffeine when compared with the Light (P=0.009) or the combination of Light and Caffeine (P= 0.0001). Average beat-to-beat intervals increased from the Baseline condition to the Light (P=0.017), Caffeine (P=0. 0.0001), and the combination of Light and Caffeine conditions (P=0.0001). All three conditions significantly reduced subjective sleepiness compared to the Baseline condition (KSS= 4–5 vs KSS=6, P= 0.0001). Conclusion: Bright light, either alone or combined with caffeine, improves driving performance and subjective sleepiness during daytime drives. Light might better improve objective sleepiness and other sleepiness indicators during nighttime when drivers are sleepier and have an increased sensitivity to the light. Further research would clarify how the circadian effects are aligned with the alerting effects of the light. Bright light, as an alternative to or combined with caffeine, could reduce sleep-related crashes on the road. Support: NA