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Xiaorui Wang, Yangcheng Gu, Jihui Yuan, Daisuke Matsushita,
Natural light control to improve awakening quality,
Building and Environment,
2025,
112733,
ISSN 0360-1323,
https://doi.org/10.1016/j.buildenv.2025.112733.
(https://www.sciencedirect.com/science/article/pii/S036013232500215X)
Abstract: Sleep is closely linked to residential environmental factors such as light, noise, and temperature. Addressing sleep problems requires realistic contributions from both architectural and medical fields. Exposure to moderate light before waking positively impacts awakening quality. Individuals are beginning to use Internet of Things (IoT) devices, like motorized curtains, to introduce natural morning light into bedrooms while avoiding nighttime light. This study aims to explore the effectiveness of controlling natural light via window equipment to improve awakening quality. In a crossover randomized controlled trial, sleepiness, alertness, and fatigue were measured in 19 participants (nine females) after waking under three different natural light exposure conditions: IA, natural light exposure for 20 minutes before waking; IB, natural light exposure from dawn to waking; CC, no natural light exposure before waking. The effects of each condition on awakening quality were analyzed. The results showed no statistically significant differences in cumulative or maximum illuminance between IA and IB. Objective alertness and subjective sleepiness in the IA and IB were significantly better than in the CC. Objective sleepiness was significantly lower in IA compared with both IB and CC. These findings suggest that natural light control through window equipment can improve awakening quality; however, excessive or early exposure could increase mid-waking time, potentially harming awakening quality. This study presents an effective method (IA) for natural light control and offers interdisciplinary insights into architecture and sleep research in real-world settings.
Keywords: Natural light control; Daylight; Sleep problems; Awakening quality; electroencephalogram; Sleep parameters

（抄録訳）睡眠は、光、騒音、室温などの居住環境要因と密接に関連している。現実の睡眠問題に対処するには建築分野の研究も貢献できる。起床前に適度な光を浴びることは目覚めの質に良い影響を与える。電動カーテンなどのIoT機器により夜間の光を避けながら自然な朝の光を寝室に取り入れることができる。目覚めの質を改善するために窓設備を介して自然光を制御することの有効性を調べることが研究の目的である。交差無作為化比較試験により19人の被験者（女性9人）を対象に次の3つの自然光曝露条件で起床後の眠気、覚醒度、疲労を測定した。介入条件IA：起床前20分間の自然光曝露、介入条件IB：夜明けから起床までの自然光曝露、対照条件CC：起床前の自然光曝露なし。結果として、IAとIBの累積照度および最大照度には統計的有意差は見られず同等性が確保されていた。IAとIBの客観的覚醒度と主観的眠気はCCよりも有意に良好で、IAの客観的眠気はIBおよびCCよりも有意に良好であった。これらの結果は窓設備による自然光制御は目覚めの質を改善すること、過剰な自然光や早朝の自然光は中途覚醒を促し目覚めの質を阻害する可能性を示唆した。以上より効果的な自然光制御方法の一つ（IA）を提示し現実の居住環境や睡眠研究に対する学際的洞察を提供した。