Moonlight may affect sleep cycles

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Urban legends have linked full moons to everything from werewolves to erratic behavior, but a new study connects them to something else — sleep loss. A Jan. 27, 2021, study in Science Advances found that people fell asleep later and slept for less time over all in the three to five days leading up to a full moon. The effect was even more pronounced in areas where people had less access to artificial light.

To come to their conclusions, researchers studied people in three communities in Argentina: one on the outskirts of a city, a small rural settlement with limited access to electricity, and a group of people in a remote area who had no access to electric light. The study authors also analyzed the sleep of 464 University of Washington students who took part in a sleep study. All participants wore sleep-tracking devices for at least one week and in some cases up to two months. The researchers compared their sleep patterns to the moon phases. Individuals took from 30 to 80 minutes longer to fall asleep during the lead-up to the full moon, and people lost anywhere from 20 minutes to 90 minutes of total sleep on those nights. The researchers said it's possible that the full moon made people more active at night, which is why sleep differences were more pronounced in communities with less access to electricity. Artificial light, they said, might produce a similar effect.

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