Combined caffeine and bright light reduces dangerous driving in sleep-deprived healthy volunteers: a pilot cross-over randomised controlled trial.

AIM OF THE STUDY: To explore the effects of caffeine and bright light therapy on simulated nighttime driving in sleep-deprived healthy volunteers. PARTICIPANTS AND METHODS: Twelve male healthy volunteers aged 20 to 50 years participated in a randomized cross-over study of simulated nighttime driving at a sleep laboratory, followed by recovery sleep with polysomnography at home. The volunteers received variable combinations of caffeine 200mg (C+), caffeine placebo (C-), bright light 10,000 lux (L+), and bright light placebo<50 lux (L-), in four sessions (C+L+, C+L-, C-L+, C-L-), in random order with a wash-out period of 7 days. Treatments were given at 1 a.m. and testing was performed at 1:30 a.m., 3 a.m., 4 a.m., and 6 a.m. Lane drifting was the primary outcome measure. Other measures were reaction times, self-rated fatigue, sleepiness and recovery sleep. RESULTS: Without treatment, lane drifting increased throughout the night, and objective and subjective vigilance declined. Paired comparisons showed that lane drifting was significantly worse at 6 a.m. and at 4 a.m. than at 1:30 a.m. There was a global treatment effect on lane drifting. Lane drifting at 6 a.m. was significantly decreased with C+L+ compared to C-L-. CONCLUSIONS: Bright light therapy combined with caffeine administered at 1 a.m. decreased lane drifting by healthy volunteers during simulated nighttime driving.