A US study provided evidence that the human circadian clock adapted to seasonal changes in the natural light-dark cycle. Reduced exposure to daytime sunlight and increased exposure to modern electrical lighting at night led to late circadian and sleep timing. Earlier circadian timing could be rapidly achieved through natural light exposure. The study showed that the beginning of the biological night and sleep occurred earlier after a week’s exposure to a natural winter 9 hr 20 min:14 hr 40 min light-dark cycle as compared to the modern electrical lighting environment. The human circadian clock was sensitive to seasonal changes in the natural light-dark cycle, showing an expansion of the biological night in winter compared to summer. Circadian and sleep timing occurred earlier after spending a weekend camping in a summer 14 hr 39 min:9 hr 21 min natural light-dark cycle compared to a typical weekend in the modern environment. Weekend exposure to natural light was sufficient to achieve ∼69% of the shift in circadian timing previously reported after a week’s exposure to natural light. Late circadian and sleep timing are associated with negative cognitive performance and health outcomes. Source: http://www.cell.com/
美国一项研究对人类生物钟适应于自然光 – 暗周期的季节性变化提供了证据。白天暴露于太阳光减少和夜间暴露于现代电气照明增加导致生物钟和睡眠时间推迟。通过暴露于自然光可使生物钟时间快速提前。该研究表明，与现代电气照明环境相比，暴露于自然的冬季9小时20分钟：14小时40分钟的光 – 暗周期一周后，生物夜及睡眠开始较早。人类生物钟对自然光 – 暗周期的季节变化敏感，与夏季相比冬季生物夜较长。与现代环境中典型的周末相比，在夏天14小时39分钟：9小时21分钟的自然光-暗周期中，一个周末的露营使生物钟及睡眠时间提前。周末暴露于自然光足以达到先前报道的经暴露于自然光一周后的生物钟时间偏移的约69％。生物钟和睡眠时间延迟与负面的认知表现和健康状况有关。来源：http://www.cell.com/
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