New evidence published in the latest issue of Current Biology, proves human beings don’t sleep as well during the full moon. The findings add to evidence that humans respond to the geophysical rhythms of the moon, driven by a circalunar clock.
"The lunar cycle seems to influence human sleep, even when one does not 'see' the moon and is not aware of the actual moon phase," says Christian Cajochen of the Psychiatric Hospital of the University of Basel.
In the new study, the researchers studied 33 volunteers in two age groups in the lab while they slept. Their brain patterns were monitored while sleeping, along with eye movements and hormone secretions. Data showed brain activity related to deep sleep dropped by 30% at the time of the full moon. 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.
"This is the first reliable evidence that a lunar rhythm can modulate sleep structure in humans when measured under the highly controlled conditions of a circadian laboratory study protocol without time cues," the researchers say.
According to Cajochen, this circalunar rhythm may have been nature’s way of synchronizing human behaviors for reproductive or other purposes, much as it does in other animals. Today, the moon's presence is masked by the influence of electrical lighting and other aspects of modern life.
Researchers are interested in looking more deeply into the anatomical location of the circalunar clock and its molecular and neuronal underpinnings, as it could affect other behaviors, including our cognitive performance and moods.
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