26th July 2013 -- Many people complain about poor sleep around a full moon. Now a study, by scientists at the University of Basel in Switzerland, offers some of the first convincing scientific evidence to suggest that lunar cycles and human sleep behaviour are in fact connected.
The findings add to evidence that humans-despite the comforts of the modern world-still respond to the rhythms of the moon.
In the new study, Professor Christian Cajochen of the Psychiatric Hospital of the University of Basel and his team studied 33 volunteers, male and female, in two age groups in the lab while they slept. Their brain patterns were monitored while sleeping, along with eye movements and hormone secretions.
The data show that around the full moon, brain activity related to deep sleep dropped by 30%. People also took 5 minutes longer to fall asleep, and they slept for 20 minutes less time overall. Study participants felt as though their sleep was poorer when the moon was full, and they showed diminished levels of melatonin, a hormone known to regulate sleep and wake cycles.
Professor Cajochen told us it wasn't what he expected to find: "I was actually very surprised. We just wanted to disprove the effect of lunar phase.
"If you look at the scientific literature, there's no proof that there is a lunar effect on human sleep, and then we were very surprised to see it."
He says they managed to see the effect through very careful measures to avoid other influences on sleep: "We used very controlled study conditions. We excluded factors like light, gravitation, individual differences in sleep-wake patterns and so on."
Blast from the past
According to the researchers, this circalunar rhythm might be a relic from past times, when the moon was responsible for synchronising human behaviour. Today, the moon's hold over us is usually masked by the influence of electrical lighting and other aspects of modern life.
Professor Jim Horne of the Sleep Research Centre at Loughborough University told us: "This is a fascinating and more robust confirmation of an earlier study. The effect was quite large, showing a 20 minute shorter sleep duration with the full moon.
"The effect is probably due to an internal 'circalunar clock' inside our brain, and not a direct effect of moonlight itself. Other animals also show something similar, and for us it seems to be a carry-over from ancient times when we were more dependent on moonlight, enabling us to see at night and spend less time asleep during the full moon when more of our predators might be out and about, or to give us more night time hunting opportunities. In our evolutionary terms, this was not very long ago."
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