1. In this study, students who took a nap after lunch felt happier, more vital, self-controlled, and less sleepy when performing cognitive tasks.
2. Amongst students exposed to bright light, there was an improvement in their working memory in a time-dependent fashion.
Evidence Rating Level: 2 (Good)
Naps and bright light exposure have been labeled as effective strategies to counter the mental fatigue associated in the afternoon, termed the “after-lunch dip”. Literature also suggested that they may impact different cognitive domains. This study aimed to investigate the effects of an after-lunch nap and bright light exposure on different cognitive domains and whether their effects were persistent over time.
Twenty healthy students who had the habit of napping midday were recruited and assessed for sleep chronotypes and disturbances, as well as physical and mental health. Students were randomized to one of three interventions held between 1:00 and 1:40 PM: bright light (at eye level), nap (in the dark), or control. Study outcomes evaluated sustained attention with a visual psychomotor vigilance task, response inhibition with a go-no-go task, and working memory with a paced visual serial addition task. Furthermore, all students completed questionnaires on subjective sleepiness, mood, vitality, and self-control. A repeat session was conducted to assess the persistent effects of bright light and napping
Students who napped reported less sleepiness, and more vitality which persisted up to 2 hours after the intervention. Furthermore, students in the nap group showed significant improvement in response inhibition and working memory in comparison to the 2 other groups. Interestingly, students exposed to bright light demonstrated improved working memory time-dependently, with a higher reaction speed in only the first session. No intervention showed improvement of sustained attention. However, this study was limited in that there were no baseline measure of cognitive assessment, and the study group was considerably homogenous. Nonetheless, this study shows that napping mid-day or self -exposure to bright light may improve task performance in various cognitive domains.
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