Objective This study of drivers in Tokyo was conducted to clarify the factors related to falling asleep and sleepiness while driving, particularly addressing short sleep duration, loud snoring or apnea witnessed by others and/or subjective sleep insufficiency.
Methods This study was conducted as a questionnaire-based cross-sectional survey. Responses from drivers who visited a driver licensing center in Tokyo were evaluated in relation to socio-demographic variables, sleep-related variables and experiences of falling asleep or feeling sleepiness while driving. The analyses included 4,097 experienced drivers.
Results Among the 4,097 drivers, 11.4% had experienced at least one incident of falling asleep while driving during the prior year and 67.6% had some prior experience of feeling sleepiness while driving. Logistic regression analyses revealed that witnessed snoring or apnea, short sleep duration and subjective insufficiency of nocturnal sleep were each independently associated with falling asleep and feeling sleepiness while driving. Subjective sleepiness while driving was associated with a sleep duration of less than six hours. However, falling asleep while driving was associated with a sleep duration of less than seven hours.
Conclusion Drivers with a sleep duration shorter than seven hours have a higher risk of falling asleep while driving without experiencing subjective sleepiness. Irrespective of perceived sleep insufficiency, drivers should sleep more than seven hours, and those suspected of having respiratory pauses during sleep should undergo sleep apnea syndrome screening.