Introduction Sleepiness Is a Major Contributing Factor in the Frequency of Highway Vehicle Crashes

SLEEPINESS IS A MAJOR CONTRIBUTING FACTOR IN THE FREQUENCY OF HIGHWAY VEHICLE CRASHES and has serious consequences as it leads to a far higher fatality rate than other factors.1,2,3,4 The available data regarding the incidence of sleepiness vary considerably from country to country according to police methods for gathering data, to the population studied, to the definition of sleepiness adopted, and to the amount of detail available on road accidents.1,3 The different estimates of the impact of sleepiness may be due in part to the fact that sleepiness often underlies other, more apparent, factors (e.g., driving speed, weather and road conditions, vehicle condition, driving habits), and weighing up the contributing role of sleepiness is extremely difficult given the multi-factor nature of many road accidents. On the other hand, the awareness of police officers about sleepiness as a factor contributing to vehicle accidents can vary greatly. This could explain the discrepancies between the low rate of road accidents ascribed to sleepiness obtained from the analysis of the databases and the higher percentage reported by field studies conducted by police officers sensitized on the importance of sleepiness as a determinant of vehicle accidents and supplied with a structured interview checklist.1,3 On the grounds of this assumption we attempted an evaluation of sleepiness as a factor contributing to the incidence of vehicle accidents by analyzing the database of vehicle accidents on the Italian highway network from 1993 to 1997. We analyzed separately the hourly distribution of accidents univocally ascribed by police officers to sleepiness and we made an attempt to evaluate, by means of a statistical estimation, the role of sleepiness as a contributing factor on vehicle accidents not directly ascribed to sleepiness on the same database.