Effects of Short and Long Nights on the Circadian Clock

描述（由申请人提供）：人们普遍认为现代社会的人们没有得到他们需要的睡眠。这种长期的睡眠债会大大降低工作效率，增加事故率，并与健康状况不佳和死亡风险增加有关。人类暴露在由自然和人造光与睡眠交替产生的明暗循环中。睡眠的持续时间决定了每日LD周期中黑暗的长度。然而，反复出现的短黑暗期（短夜）对人类昼夜节律系统的影响尚不清楚。有人提出，哺乳动物有一个复杂的昼夜节律起搏器，包括一个晚上的振荡器，调节褪黑激素分泌的开始，和一个早晨的振荡器，调节褪黑激素分泌的抵消。在较短的夏夜（较长的光周期），晚上和早晨振荡之间的相位关系减少，这缩短了夜间褪黑素谱的持续时间，反过来调节适当的季节变化。其他动物实验表明，在较短的夜晚，光相响应曲线的范围和幅度减小。

DESCRIPTION (provided by applicant): It is widely recognized that humans in modern society do not get the sleep they need. This chronic sleep debt significantly degrades productivity, increases accident rates and has been linked to poor health and increased risk of death. Humans are exposed to a light dark (LD) cycle created by natural and artificial light alternating with sleep. Sleep duration determines the length of dark in the daily LD cycle. However, the effects of repeated short dark periods (short nights) on the human circadian system remain unknown. It has been proposed that mammals have a complex circadian pacemaker, consisting of an evening oscillator, that regulates the onset of melatonin secretion, and a morning oscillator, that regulates the offset of melatonin secretion. In short summer nights (longer photoperiods), the phase relationship between the evening and morning oscillators is decreased, which shortens the duration of the nocturnal melatonin profile, in turn regulating appropriate seasonal changes. Other animal work shows that the range and amplitude of the light phase response curve is decreased in short nights. We propose to investigate the effects of short and long nights on the human circadian system, by keeping subjects in bed, in the dark, for either 6 or 9 hours per night. We will determine if the duration of the melatonin rhythm in dim light compresses after a history of short nights, and expands after a history of long nights, thus revealing that the circadian pacemaker has a memory of the previous night length. We will also determine if a history of short nights reduces the phase shifting response to light. Our goal is to determine the extent to which the chronic sleep debt in modern society is altering the functioning of the human circadian system. This work has important implications for the sleep deprived general population and for jet travelers and night shift workers who must phase shift their circadian rhythms in order to adjust to phase shifts in their light/dark cycle.