Effect of Coffee Intake on Heat Rate Variability and Driving Performance in Sleep-deprived Condition

This driving simulation study investigates the effect of coffee intake as a countermeasure on sleepiness and driving performance decrement in sleep-deprived condition. Twelve university students (mean age of $21.2 \pm 0.2$ years) drove following an urban route after 24 h sleep deprivation without drinking coffee or with a cup coffee containing 89.4 mg caffeine in two separate days and random order. Sleepiness level was assessed employing a subjective sleepiness scale and heart rate variability. The results show that consuming a cup of coffee before driving in sleep-deprived condition may enhance sympathetic nerve activities and improve driving performance. From these findings, it suggests that consuming coffee may be useful as sleepiness countermeasure in a sleep-deprived condition.