Abstract: Sleep inertia is a process from sleep to fully wake up. The transition entails a temporary period of confusion, disorientation, reduced alertness, bad affect and poor task performance. Previous studies have focused more attention on the pharmacological ways (e.g., caffeine, excitant) of counteracting sleep inertia. However, there is little study investigating the non-pharmacological ways such as light exposure on the impact of sleep inertia post awakening up to now. The aim of the current study was using behavior and PSG technique to explore the effect of morning sleep inertia on subjective alertness and mood as well as cognitive performance in young healthy adults. We also examined whether exposure to dynamic dawn-simulated light could be a valid countermeasure against the detrimental effects of sleep inertia after waking up in the morning. A single factor within-subject design with lighting condition (at eye level) as independent variable was used in the present study. Three different light settings (separated by 1wks) were administered each morning after one 6-h sleep restriction night: a dawn-simulating light (starting 30min before scheduled wake-up time, polychromatic light gradually increasing from 0 to 210lux), a constant light (40lux for 30min before scheduled wake-up time) and a control condition (no any light exposure prior to wake up). 21 college students (9 males) participated in the study based on strict selection criteria such as chronotype, medical and sleep disorders, general health, life habits, affective disorders, smoking, drug consumption, body mass index, shift work and transmeridian ?ights during last two months. Sleep inertia was measured by a 2-h test protocol since wakeup, including subjective ratings of alertness and mood, and by performance on a psychomotor vigilance task (PVT), a 2-back and a go/no-go task. Results were as follows: A paired t-test between baseline and the first post-sleep assessment revealed a significant difference in both KSS and PANAS scores such that subjective alertness and positive mood immediately after awakening were much lower than at baseline, thereafter it declined over a two-hour period as indicated by a significant effect of time. Performance on PVT, 2-back and go/no-go tasks were founded to be significantly worse at the first test after waking up than at baseline, and the effect of sleep inertia on these tasks dissipated over the course of two hours as indicated by a significant effect of time in the analysis of variance. Moreover, performance speed was more impaired than accuracy. Compared with control and constant light condition, the dawn simulation light resulted in a significant improvement of subjective alertness and positive mood after waking up. Similarly, response times on PVT and accuracy on go/no-go task were much faster and higher respectively in the artificial dawn condition relative to the control and constant light. However, the light conditions had no differential effects on negative mood and the 2-back task. These findings suggest that morning sleep inertia had a significant negative effect on subjective alertness and positive affect as well as some cognitive functions like sustained attention, working memory and inhibitory capacity. The use of simulated dawn light could to some extent help counteract sleep inertia after awakening in the morning, which effect was highly related to the light pattern with a dynamic exponential change.

Key words: dawn simulation, sleep inertia, cognitive performance, subjective alertness, mood

摘要： 本研究采用单因素被试内设计对清晨唤醒后睡眠惰性对个体主观情绪、警觉性和认知加工的影响，以及利用动态黎明模拟光照能否对睡眠惰性产生有效的对抗作用进行了考察。结果发现：（1）被试的积极情绪、主观警觉性在刚唤醒时显著低于基线水平，之后随时间推移逐渐提升。（2）被试醒后立即进行测试的认知加工成绩最差，随后逐渐提高，且主要表现在加工速度的回升上。（3）黎明模拟光照对被试醒后在积极情绪、主观警觉性、持续性注意和抑制功能的缓解上产生了明显的促进作用。这表明睡眠惰性会对个体的主客观活动产生显著的负性影响，而使用黎明模拟光照可在一定程度上对抗睡眠惰性带来的负性影响。

关键词: 黎明模拟光照 睡眠惰性 认知加工 主观警觉性 情绪