Sleepiness and motor vehicle crashes in a representative sample of Portuguese drivers: The importance of epidemiological representative surveys

Objective: Sleepiness is considered to be a leading cause of crashes. Despite the huge amount of information collected in questionnaire studies only some are based on representative samples of the population. Specifics of the populations studied hinder the generalization of these previous findings. For the Portuguese population, data from sleep related car crashes/near misses and sleepiness while driving is missing. The objective of this study is to determine the prevalence of near-miss and non-fatal motor-vehicle crashes related to sleepiness in a representative sample of Portuguese drivers. Methods: Structured phone interview regarding sleepiness and sleep related crashes and near-misses, driving habits, demographic data, sleep quality using the Pittsburgh Sleep Quality Index and sleep apnea risk using the Berlin questionnaire. A multivariate regression analysis was used to determine the associations with sleepy driving (feeling sleepy or falling asleep while driving) and sleep related near-misses and crashes. Results: 900 subjects, representing the Portuguese population of drivers, were included. 3.1% acknowledged falling asleep while driving during the previous year; 0.67% recalled sleepiness-related crashes. Higher education, driving more than 15000 km/year, driving more frequently between 0 and 6 AM, fewer years of having a drivers license, less total sleep time per night and higher scores on the Epworth Sleepiness Scale (ESS) were all independently associated with sleepy driving. Sleepiness related crashes and near misses were associated only with falling asleep at the wheel in the previous year. Sleep related crashes occurred more frequently in drivers that had also had sleep related near misses. Conclusion: Portugal has lower self-reported sleepiness at the wheel and sleep related near-misses than most other countries where epidemiological data is available. Different population characteristics, cultural, social and road safety specificities may be involved in these discrepancies. Despite this, Portuguese drivers report sleep related crashes in frequencies similar to drivers in other countries.