Centre for Chronobiology, Psychiatric Hospital of the University of Basel, Basel, Switzerland.
Chronobiol Int. 2013 Oct;30(8):988-97. doi: 10.3109/07420528.2013.793196. Epub 2013 Jul 10.
Light exposure elicits numerous effects on human physiology and behavior, such as better cognitive performance and mood. Here we investigated the role of morning light exposure as a countermeasure for impaired cognitive performance and mood under sleep restriction (SR). Seventeen participants took part of a 48h laboratory protocol, during which three different light settings (separated by 2 wks) were administered each morning after two 6-h sleep restriction nights: a blue monochromatic LED (light-emitting diode) light condition (BL; 100 lux at 470 nm for 20 min) starting 2 h after scheduled wake-up time, a dawn-simulating light (DsL) starting 30 min before and ending 20 min after scheduled wake-up time (polychromatic light gradually increasing from 0 to 250 lux), and a dim light (DL) condition for 2 h beginning upon scheduled wake time (<8 lux). Cognitive tasks were performed every 2 h during scheduled wakefulness, and questionnaires were administered hourly to assess subjective sleepiness, mood, and well-being. Salivary melatonin and cortisol were collected throughout scheduled wakefulness in regular intervals, and the effects on melatonin were measured after only one light pulse. Following the first SR, analysis of the time course of cognitive performance during scheduled wakefulness indicated a decrease following DL, whereas it remained stable following BL and significantly improved after DsL. Cognitive performance levels during the second day after SR were not significantly affected by the different light conditions. However, after both SR nights, mood and well-being were significantly enhanced after exposure to morning DsL compared with DL and BL. Melatonin onset occurred earlier after morning BL exposure, than after morning DsL and DL, whereas salivary cortisol levels were higher at wake-up time after DsL compared with BL and DL. Our data indicate that exposure to an artificial morning dawn simulation light improves subjective well-being, mood, and cognitive performance, as compared with DL and BL, with minimal impact on circadian phase. Thus, DsL may provide an effective strategy for enhancing cognitive performance, well-being, and mood under mild sleep restriction.
光照对人类生理和行为有诸多影响，例如提高认知表现和改善情绪。在这里，我们研究了晨光暴露作为改善睡眠限制（SR）下认知表现和情绪受损的对策的作用。17 名参与者参与了一个 48 小时的实验室方案，在该方案中，每天早晨在两次 6 小时的睡眠限制后，通过三种不同的光照设置（间隔 2 周）进行干预：一种是蓝色单色 LED（发光二极管）光条件（BL；在 470nm 处为 100lux，持续 20 分钟），在计划醒来时间后 2 小时开始，一种是模拟黎明的光（DsL），在计划醒来时间前 30 分钟开始，在计划醒来时间后 20 分钟结束（多色光逐渐从 0 增加到 250lux），以及一种昏暗的光（DL）条件，在计划醒来时间开始，持续 2 小时（<8lux）。在计划清醒期间，每 2 小时进行一次认知任务，并每小时进行一次问卷调查，以评估主观困倦、情绪和幸福感。在有规律的间隔内收集整个计划清醒期间的唾液褪黑素和皮质醇，并在仅接受一次光脉冲后测量褪黑素的影响。在第一次 SR 之后，对计划清醒期间认知表现的时间进程进行分析表明，DL 后认知表现下降，而 BL 和 DsL 后认知表现保持稳定，DsL 后显著改善。第二次 SR 后，不同光照条件对认知表现水平没有显著影响。然而，在两次 SR 夜间之后，与 DL 和 BL 相比，暴露于早晨 DsL 后，情绪和幸福感显著增强。与早晨 DsL 和 DL 相比，早晨 BL 暴露后褪黑素的出现时间更早，而 DsL 后醒来时唾液皮质醇水平更高。我们的数据表明，与 DL 和 BL 相比，暴露于人工早晨黎明模拟光可改善主观幸福感、情绪和认知表现，对昼夜节律相位的影响最小。因此，DsL 可能是在轻度睡眠限制下提高认知表现、幸福感和情绪的有效策略。
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