Daytime Sleepiness Is Widespread and Has a Negative Impact on Everyday Life.1 up to 20% of All Traffic Accidents in Industrial Societies Are

DAYTIME SLEEPINESS IS WIDESPREAD AND HAS A NEGATIVE IMPACT ON EVERYDAY LIFE.1 UP TO 20% OF ALL TRAFFIC ACCIDENTS IN INDUSTRIAL SOCIETIES ARE sleep related.2-4 Connor et al3 have shown that driving between 02:00 and 05:00 multiplies by 5.6 the risk of traffic accidents. Despite this, many people persistently repeat this dangerous behavior because of financial reasons in professional drivers5 or sociocultural factors.6,7 Traffic accidents at work or during the trip from work to home are a major cause of injury and death among workers.8,9 Young medical residents are often victims of sleep-related traffic accidents10 and/ or are involved in medical errors11 related to extensive hours of work associated with sleep deprivation. Young people are clearly overrepresented in sleep-related accidents,4,12,13 but the question of overexposure to the risk or increased vulnerability to sleep-related accidents has not yet been clarified. Past studies have shown that young people are more vulnerable to sleep loss than are middle-aged people,14-16 but young people are also very exposed to sleep deprivation,7,10,17 which could explain the high percentage of young drivers involved in sleep-related accidents. Responsiveness to countermeasures to sleepiness at the wheel might also be different among age groups. Such countermeasures include the use of awakening agents such as caffeine or napping. Caffeine is a widely used substance mainly consumed in coffee and similar beverages. It has been estimated that adults in western societies have an average all-source daily caffeine intake of about 200 to 300 mg18 and that these amounts increase with age.19 Within this dose range and at higher levels, caffeine increases alertness and acutely reduces sleep propensity. Napping is also a well-known countermeasure to combat fatigue, and countermeasures significantly improve nocturnal driving performances in young drivers.20 Because middle-aged people respond differently than young people to sleep deprivation,14,15,21 we decided to test the influence of age on the response to sleepiness countermeasures. To test this hypothesis, we designed a randomized, partially double-blinded, crossover study of the effects of coffee and napping in young and middle-aged participants on nighttime highway driving.