In-car nocturnal blue light exposure improves motorway driving: a randomized controlled trial

PLoS One. 2012;7(10):e46750. doi: 10.1371/journal.pone.0046750. Epub 2012 Oct 19.

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.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Automobile Driving*
  • Caffeine / pharmacology
  • Coffee / chemistry
  • Cross-Over Studies
  • Double-Blind Method
  • Fatigue / prevention & control*
  • Humans
  • Light
  • Male
  • Middle Aged
  • Photic Stimulation*
  • Placebos
  • Psychomotor Performance / drug effects
  • Psychomotor Performance / radiation effects
  • Reproducibility of Results
  • Sleep Deprivation
  • Sleep Stages / radiation effects
  • Wakefulness / drug effects
  • Wakefulness / physiology
  • Wakefulness / radiation effects*

Substances

  • Coffee
  • Placebos
  • Caffeine

Associated data

  • ClinicalTrials.gov/NCT01070004