Prevalence of driver sleepiness in a random population-based sample of car driving

Study Objectives: To obtain reliable estimates of the prevalence of driver sleepiness. Design: A two-stage cluster sampling technique was employed to obtain a sample of car drivers representative of time spent driving on public roads in a geographically defined region. Data were collected by interviewer-administered questionnaire, and analysed in accordance with the sampling design. Setting: The Auckland region of New Zealand, between April 1998 and July 1999. Participants: 588 drivers of cars and other light vehicles recruited at 69 roadside survey sites. Measurements and Results: Of 746 eligible participants, 79% were interviewed, 12% refused, 8% were untraceable, and 1% were unable to give informed consent. From this sample we estimated that 58.7% of driving was undertaken by men. The vast majority of driving (90.8%) was undertaken by drivers with Epworth Sleepiness scores in the normal range (<10), but a significant minority was undertaken by drivers with one or more characteristics likely to impair alertness. 3.1% had <less than or equal to>5 hours sleep in the previous 24 hours, and 21.9% had less than or equal to4 full nights sleep In the previous week. The triad of symptoms associated with sleep apnea. (snoring, choking, and breathing pauses while sleeping) was present in 1.6%; and 8.1% worked a pattern of shifts likely to interfere with normal sleep. Conclusion: The prevalence of sleepiness amongst a random sample of New Zealand car driving was low, and less than suggested by previous studies.