Study Objectives: Real life ocular measures of drowsiness use average blink duration, amplitude and velocity of eyelid movements to reflect drowsiness in drivers. However, averaged data may conceal the variability in duration of eyelid closure episodes, and more prolonged episodes that indicate higher levels of drowsiness. The current study aimed to describe the frequency and duration of prolonged eyelid closure episodes during acute sleep deprivation. Methods: Twenty male professional drivers (mean age ± standard deviation = 41.9 ± 8.3 years) were recruited from the Transport Workers Union newsletter and newspaper advertisements in Melbourne, Australia. Each participant underwent 24 hours of sleep deprivation and completed a simulated driving task (AusEd), the Psychomotor Vigilance Task, and the Karolinska Sleepiness Scale. Eyelid closure episodes during the driving task were recorded and analyzed manually from digital video recordings. Results: Eyelid closure episodes increased in frequency and duration with a median of zero s/h of eyelid closure after 3 h increasing to 34 s/h after 23 h awake. Eyelid closure episodes were short and infrequent from 3 to 14 h of wakefulness. After 17 h of sleep deprivation, longer and more frequent eyelid closure episodes began to occur. Episodes lasting from 7 seconds up to 18 seconds developed after 20 h of wakefulness. Length of eyelid closure episodes was moderately to highly correlated with the standard deviation of lateral lane position, braking reaction time, crashes, impaired vigilance, and subjective sleepiness.
Conclusions:The frequency and duration of episodes of prolonged eyelid closure increases during acute sleep deprivation, with very prolonged episodes after 17 hours awake. Automated devices that assess drowsiness using averaged measures of eyelid closure episodes need to be able to detect prolonged eyelid closure episodes that occur during more severe sleep deprivation. Keywords: drowsiness, sleepiness, eyelid closure episodes, professional drivers, averaged data, automated devices Citation: Alvaro PK, Jackson ML, Berlowitz DJ, Swann P, Howard ME. Prolonged eyelid closure episodes during sleep deprivation in professional drivers.
I NTRO DUCTI O NSleep deprivation and resultant drowsiness are common causes of impaired performance and motor vehicle accidents (MVA) in both the general population and professional drivers.1,2 A lack of real-time drowsiness measures has hampered efforts to develop and assess interventions for sleep deprivation. Objective measures of real-time drowsiness that accurately identify sleepy individuals before and during driving events can potentially prevent MVAs by alerting the driver to significant drowsiness levels and in turn suggest the use of countermeasures, such as a nap or caffeine. They would also provide an opportunity to evaluate the impact of different driving schedules, identifying high risk schedules that result in drowsy driving and assisting with the design of safer work schedules.Slow, prolonged eyelid closure is associa...