Study objectives: Although sleepiness appears to heighten distraction from the task at hand, especially if the latter is dull and monotonous, this aspect of sleep loss has not been assessed in any systematic way. Distractions are a potential cause of performance lapses (as are micro-sleeps). Here, we investigate the effects of sleepiness on a monotonous task, with and without distraction.
Design: Repeated Measures 2 x 2 counterbalanced design, comprising Sleepiness (night sleep restricted to 5 hours x normal sleep) and Distraction (distraction x no distraction).
Setting: Participants underwent 30-minute sessions on the Psychomotor Vigilance Test (2:00 PM - 3:10 PM), with or without an attractive distraction to be ignored, under normal and sleep-restricted conditions.
Participants: Sixteen healthy young adults (mean age 21.10 years; 21-25 years [8 men; 8 women]) without any sleep or medical problems and without any indication of daytime sleepiness.
Interventions: Normal sleep versus sleep restricted to 5 hours and distraction versus no distraction. Distraction comprised a television in the visual periphery, showing an attractive video that had to be ignored.
Measurements and results: Psychomotor Vigilance Test performance was monitored, as were the participants' head turns toward the television via videocameras. There was a significant increase in both head turns and lapses during sleep restriction plus distraction. Moreover, sleepiness also increased head turns even during no distraction. Distracting effects of sleepiness were clearly evident during the initial 10 minutes of testing.
Conclusions: Distractibility is an important aspect of sleepiness, which has relevance to safety in the real world, eg, sleepy driving.