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 　　The lunar cycle affects the night sky, the tides, and even the fertility of certain marine¹ species. And it turns out, we can add your shuteye to the list. According to a new study, humans sleep poorly on nights near full moon. The work is published in the journal Current Biology. To test the moon's effect, 33 adult volunteers of both sexes and various ages spent several nights in the sleep lab. As they dozed², researchers monitered their brain activity, eye movements, and hormone³ levels. On nights closer to a full moon, the subjects took an average of five minutes longer to fall asleep and slept for 20 minutes less. In addition, brain activity decreased by 30% during the sleep stage that the brains normally uses to recover from its daylight work. And levels of melatonin, the horomone that helps regulate sleep cycles, dropped. On these nights, the sleepers⁴ complained of poor sleep quality, even though they were unaware⁵ of the lunar cycle. On the bright side, not a single participant turned into a werewolf in this cohort.