Regulation of Circadian Rhythms and Sleep by The Lunar Month

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PROJECT SUMMARY Throughout evolution and history humans have progressively isolated themselves from the natural cycles by building artificial habitats that shield them from the external environment. This has vastly affected when and how much humans sleep, especially since the near universalization of electric light. The key to this isolation and change in sleep patterns is the ability to manipulate artificial light and extend activity into the nighttime. A recent study from our laboratory found that the timing of sleep changes across the moon cycle, with later and shorter events of night sleep on the nights leading up to the full moon. Surprisingly, we found this lunar cycle modulation not only in rural but also in urban environments. Sleep is controlled by two simultaneous processes: the circadian clock determines the optimal times for sleep throughout the 24-h cycle while the homeostatic drive for sleep increases as we stay awake. The two processes combine to determine the natural human patterns of night sleep. This project aims to determine which of these two mechanisms that regulate sleep is affected throughout the moon cycle to delay and shorten sleep on the nights before full moon. We will combine longitudinal field recordings of sleep and sleep laboratory strategies to address the following two aims: Specific Aim 1: Assess circadian phase at opposite phases of the moon cycle in Toba/Qom communities. We will conduct longitudinal monitoring of sleep in rural and urban native Toba/Qom communities in northern Argentina. In individuals with robust lunar patterns we will assess the phase of the dim-light melatonin onset (DLMO), the gold- standard for determining circadian phase in humans, in the days leading to the full and new moons. Our hypothesis is that the phase of the circadian clock is modulated across the moon cycle, and predicts that the DLMO phase will be delayed on the days preceding the full moon relative to the pre-new moon days. Specific Aim 2: Assess circadian phase, and circadian and homeostatic regulation of sleep at opposite phases of the moon cycle in a highly urbanized community. We have already confirmed that this lunar modulation is present even in industrialized societies, where artificial light during the evening reigns over the full moon’s light. We will screen Seattle participants through longitudinal sleep monitoring and select those with the most robust lunar rhythms to participate in sleep laboratory visits twice at the opposite phases of the moon cycle. We will use polysomnographic wake and sleep recordings, as well as a constant routine protocol to study the potential lunar monthly change in circadian phase and in the homeostatic regulation of sleep after sleep deprivation. Whether the moon can affect sleep has been a matter of high controversy for decades. Our recent work demonstrated that sleep patterns vary across the moon cycle in a very predictable manner in real life conditions, in very different populations and under different environments. This project aims to shed light on the mechanisms through which this modulation occurs, which will further our understanding of the regulation of human sleep, and its impact on health and disease.