A July 2013 study correlates the full moon and and human sleep quality. University of Basel in Switzerland Professor Cajochen and colleagues found that a lunar rhythm can modulate sleep structure in humans when carefully measured even though the 33 volunteer subjects did not have time cues. The study controlled for things that affect sleep like increased light at night or the potential bias in perception. Subjective and objective measures of sleep varied according to lunar phase and thus may reflect human circalunar rhythmicity.
Measures of lunar influence on sleep structure, electroencephalographic activity during non-rapid eye movement sleep (NREM), and secretion of the hormones melatonin and cortisol, were retrospectively analyzed. At no point, during and after the study, were volunteers or investigators aware of the posteriori analysis relative to lunar phase.
Around full moon it was found that:
- electroencephalogram (EEG) delta activity during NREM sleep, an indicator of deep sleep, decreased by 30%,
- time to fall asleep increased by five minutes, and
- EEG-assessed total sleep duration was reduced by 20 minutes.
- subjective sleep quality decreased
- endogenous melatonin levels decreased
Cajochen said: “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.”