People take longer to doze off, sleep less deeply, and sleep for a shorter time in the days close to a full moon, according to a new study posted online in Current Biology on Sunday. Using electroencephalograms (EEG) that measure brain activity, researchers from the University of Basel in Switzerland recorded how deep and how long each volunteer\'s nightly sleep was in a controlled, laboratory setting. While the data on the sleep patterns of 33 healthy volunteers was recorded and analyzed for a study on the effects of aging on sleep, researchers had a happy accidental founding, a striking association between poor sleep and lunar cycles. In the few days before and after a full moon, people took an average of five extra minutes to fall asleep, slept 20 minutes less per night, and had 30 percent less deep sleep, as measured by the EEG. \"A lot of people are going to say, \'Yeah, I knew this already. I never sleep well during a full moon.\' But this is the first data that really confirms it,\" says biologist Christian Cajochen of the University of Basel. What is the mechanism behind this phenomenon likely lies in moon light or other external factors, which influence human internal hormones, like people\'s 24-hour sleep-wake cycles, which persist even in the absence of light or darkness, Cajochen speculates. \"In terms of the lunar cycle, light could be important to synchronize this biological clock with environmental stimuli,\" Cajochen says.