The challenge of studying the moon and sleepUntangling the moon’s effects on human sleep isn’t easy. A second Swiss study of 47 healthy adults found similar results: Participants slept 25 minutes less around the full moon. The researchers also noticed that participants took 30 minutes longer to reach the REM sleep phase (i.e. During a sleep study, participants sleep in sterile, medical settings that can skew data. “The ability of the moon to decrease total sleep time, by up to one hour, is quite profound.