Cerebral Perfusion in Drowsy and Nondrowsy Individuals

1085 Cerebral Perfusion and Drowsiness—Poudel et al INTRODUCTION Lack of sufficient sleep can increase drowsiness and tendency to fall asleep during the day. Increased sleepiness is often manifested as response slowing, behavioral lapses,1-3 and changes in ocular and facial behaviors including droopy eyes, slow eyelid closure, head nodding, and loss of facial tone.4-6 Although total sleep deprivation of 24 h or more substantially impairs neurobehavioral functioning,7,8 an acute reduction in sleep to 4-6 h (sleep restriction) is sufficient to increase tendency to fall asleep during monotonous situations.9-13 Due to shift work, extended work hours, and jet lag, sleep restriction is also more common than total sleep deprivation in everyday life. The increased tendency to fall asleep after sleep loss can compromise an individual’s and public safety, particularly in occupations such as truck drivers, locomotive drivers, pilots, air-traffic controllers, and process-control workers.14,15 For the measurement of behavioral alertness, previous work has relied on reaction time and response error during a sustained attention task,6,16,17 self-rating of sleepiness,18-20 or observer-ratCEREBRAL PERFUSION IN DROWSY AND NONDROWSY INDIVIDUALS