Abstract
Prolonged wakefulness greatly decreases nocturnal driving performance. The development of in-car countermeasures is a future challenge to prevent sleep-related accidents. The aim of this study is to determine whether continuous exposure to monochromatic light in the short wavelengths (blue light), placed on the dashboard, improves night-time driving performance. In this randomized, double-blind, placebo-controlled, cross-over study, 48 healthy male participants (aged 20–50 years) drove 400 km (250 miles) on motorway during night-time. They randomly and consecutively received either continuous blue light exposure (GOLite, Philips, 468 nm) during driving or 2*200 mg of caffeine or placebo of caffeine before and during the break. Treatments were separated by at least 1 week. The outcomes were number of inappropriate line crossings (ILC) and mean standard deviation of the lateral position (SDLP). Eight participants (17%) complained about dazzle during blue light exposure and were removed from the analysis. Results from the 40 remaining participants (mean age ± SD: 32.9±11.1) showed that countermeasures reduced the number of inappropriate line crossings (ILC) (F(2,91.11) = 6.64; p<0.05). Indeed, ILC were lower with coffee (12.51 [95% CI, 5.86 to 19.66], p = 0.001) and blue light (14.58 [CI, 8.75 to 22.58], p = 0.003) than with placebo (26.42 [CI, 19.90 to 33.71]). Similar results were found for SDLP. Treatments did not modify the quality, quantity and timing of 3 subsequent nocturnal sleep episodes. Despite a lesser tolerance, a non-inferior efficacy of continuous nocturnal blue light exposure compared with caffeine suggests that this in-car countermeasure, used occasionally, could be used to fight nocturnal sleepiness at the wheel in blue light-tolerant drivers, whatever their age. More studies are needed to determine the reproducibility of data and to verify if it can be generalized to women.Trial Registration ClinicalTrials.gov NCT01070004
Highlights
Our society induces behavioural reduction of daily sleep duration and extensive periods of wakefulness or activities in the circadian deep (3–5 a.m.) which are causes of sleepiness-related accidents [1], especially traffic accidents
Three incomplete driving sessions were under placebo, 2 under coffee and 3 under continuous blue light exposure
As some participants complained about dazzle during continuous blue light exposure and as the variability of driving performance (ILC) was high for this driving condition [Standard error (SE) for Blue light = 6.15, for Placebo = 5.12 and for Coffee = 2.72)], a hierarchic classification based on the Ward method was used to check whether all participants performed
Summary
Our society induces behavioural reduction of daily sleep duration and extensive periods of wakefulness or activities in the circadian deep (3–5 a.m.) which are causes of sleepiness-related accidents [1], especially traffic accidents. Owing to conflicts between physiological needs and social [2] or professional activities, countermeasures to fight this sleepiness need to be developed. Caffeine and naps have been shown to be effective in real-life driving studies [3,4] but they have some limitations (differences between individuals in terms of efficiency, limited efficiency duration, side-effects). Caffeine and nap, selfadministered countermeasures that involve stopping the car at rest stops, are not adequate because a study has shown that many sleepy drivers (46%) continue to drive [5]. The development and evaluation of in-car and preventive countermeasures is a major public health issue for the prevention sleepiness-related accidents
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