Temporal Dynamics of Subjective and Objective Alertness During Exposure to Bright Light in the Afternoon for 5 h

Xue Luo; Taotao Ru; Qingwei Chen; Fan-Chi Hsiao; Ching-Sui Hung; Chien-Ming Yang; Guofu Zhou

doi:10.3389/fphys.2021.771605

Temporal Dynamics of Subjective and Objective Alertness During Exposure to Bright Light in the Afternoon for 5 h

Front Physiol. 2021 Dec 7:12:771605. doi: 10.3389/fphys.2021.771605. eCollection 2021.

Authors

Xue Luo¹, Taotao Ru^{2

3}, Qingwei Chen^{2

3}, Fan-Chi Hsiao⁴, Ching-Sui Hung⁵, Chien-Ming Yang^{5

6}, Guofu Zhou^{2

3}

Affiliations

¹ School of Psychology, South China Normal University, Guangzhou, China.
² Lab of Light and Physiopsychological Health, National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou, China.
³ Guangdong Provincial Key Laboratory of Optical Information Materials and Technology and Institute of Electronic Paper Displays, South China Normal University, South China Academy of Advanced Optoelectronics, Guangzhou, China.
⁴ Department of Counseling and Industrial/Organizational Psychology, Ming Chuan University, Taoyuan, Taiwan.
⁵ Department of Psychology, National Chengchi University, Taipei, Taiwan.
⁶ The Research Center for Mind, Brain, and Learning, National Chengchi University, Taipei, Taiwan.

Abstract

Light can induce an alertness response in humans. The effects of exposure to bright light vs. dim light on the levels of alertness during the day, especially in the afternoon, as reported in the literature, are inconsistent. This study employed a multiple measurement strategy to explore the temporal variations in the effects of exposure to bright light vs. regular office light (1,200 lx vs. 200 lx at eye level, 6,500 K) on the alertness of participants for 5 h in the afternoon. In this study, 20 healthy adults (11 female; mean age 23.25 ± 2.3 years) underwent the Karolinska sleepiness scale (KSS), the auditory psychomotor vigilance test (PVT), and the waking electroencephalogram (EEG) test for two levels of light intervention. The results yielded a relatively lower relative delta power and a relatively higher beta power for the 1,200 lx condition in comparison with the 200 lx condition. However, the light conditions elicited no statistically significant differences in the KSS scores and performance with respect to the PVT. The results suggested that exposure to bright light for 5 h in the afternoon could enhance physiological arousal while exerting insignificant effects on subjective feelings and performance abilities relating to the alertness of the participants.

Keywords: alertness; electroencephalogram; illumination; light; light exposure.