2.3. Questionnaires
Sleepiness, sleepiness, daytime mood, fatigue
The daytime mood, including perceived sleepiness, physical fatigue, motivation, attention, and optimism, was surveyed using a visual analog scale (VAS) ranging from 0 mm for “severely unfavorable” daytime performance to 100 mm for “supremely favorable”. Sleepiness was also evaluated on a 9-point Likert scale using the Karolinska Sleepiness Scale (KSS) [