In-Car Nocturnal Blue Light Exposure Improves Motorway Driving: A Randomized Controlled Trial

Taillard, Jacques; Capelli, Aurore; Sagaspe, Patricia; Anund, Anna; Åkerstedt, Torbjörn; Philip, Pierre · 2012 · OpenAlex-citations

DOI: 10.1371/journal.pone.0046750

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Summary

This randomized, double-blind, placebo-controlled crossover trial investigated whether continuous exposure to monochromatic blue light (468 nm) during nocturnal driving improves motorway driving performance compared to caffeine and placebo. The study was motivated by the high prevalence of sleep-related traffic accidents and the limitations of existing countermeasures, such as caffeine and naps, which require drivers to stop or have variable efficacy. The researchers aimed to evaluate blue light as a potential in-car preventive countermeasure that can be used continuously while driving. The study involved 48 healthy male participants aged 20–50 years. Each participant completed three driving sessions, separated by at least one week, during which they drove 400 km on a motorway between 1:00 AM and 5:15 AM. The sessions were randomized to receive either continuous blue light exposure from a dashboard-mounted device, two doses of 200 mg caffeine (coffee), or a caffeine placebo. Primary outcomes were the number of inappropriate line crossings (ILC) and the standard deviation of lateral position (SDLP), which measure lane-keeping ability and weaving. Eight participants who reported dazzle or discomfort from the blue light were excluded from the final analysis, leaving 40 participants. Statistical analyses used mixed-model approaches to account for serial correlations and individual variability. The results demonstrated that both blue light exposure and caffeine significantly improved driving performance compared to placebo. Specifically, the mean number of inappropriate line crossings was significantly lower for the blue light condition (14.58) and coffee condition (12.51) than for the placebo condition (26.42). Similarly, both interventions reduced the standard deviation of lateral position, indicating more stable lane keeping. The efficacy of blue light was non-inferior to caffeine. No significant differences were found between young and middle-aged drivers, suggesting the intervention works across these age groups. Additionally, the countermeasures did not affect the quality, quantity, or timing of the three subsequent nocturnal sleep episodes recorded via actigraphy. The study concludes that continuous nocturnal blue light exposure is an effective in-car countermeasure for combating driver sleepiness, offering efficacy comparable to caffeine without disrupting subsequent sleep. However, the authors note that 17% of participants experienced visual discomfort or dazzle, which impaired their driving performance. Therefore, the intervention is recommended only for drivers who tolerate blue light well. The findings suggest that blue light could be a viable tool for preventing sleep-related accidents, particularly for drivers who cannot stop for naps or prefer non-pharmacological interventions. The authors call for further research to verify reproducibility and to determine if these effects generalize to female drivers, as the current study was limited to men.

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Topics

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• dark adaptation mesopic
• circadian factors
• sleep deprivation