OBJECTIVE: To determine whether self-reported drowsy driving was associated with an evening chronotype, a biologically-based difference in circadian sleep-wake timing, and shorter school-night sleep duration in a sample of high school drivers.
STUDY DESIGN: Cross-sectional observational data were obtained from an online survey in spring 2015 of 431 drivers, age 15.5-18.7 years, attending Fairfax County (Virginia) Public schools. Drowsy driving was defined as having ever "driven a car or motor vehicle while feeling drowsy" in the last year. School-night sleep duration was calculated from school-night bedtime and wake time. Those with scores in the lower and upper tertiles of the Morningness-Eveningness Scale for Children were designated as having an evening or morning chronotype, respectively.
RESULTS: Among survey respondents, 63.1% drove at least several times a week and 47.6% reported drowsy driving. The covariate-adjusted prevalence of drowsy driving was 13.9% (95% CI 3.0%-24.9%) higher in students who slept <7 hours on school-nights than in those who slept 8 or more hours. Compared with those with a morning chronotype, the adjusted prevalence of drowsy driving was 15.2% (95% CI 4.5%-25.9%) higher among those with an evening chronotype.
CONCLUSION: Among adolescent drivers, both an evening chronotype and shorter school-night sleep duration were associated with more frequent reports of drowsy driving. Interventions to improve the timing and duration of nighttime sleep in adolescents may reduce the occurrence of drowsy driving.
