Scientists have long understood how much human activity is associated with light, whether solar, lunar, or artificial. According to researchers who have now studied sleep patterns in people living in both urban and rural environments with different access to electricity, the lunar cycle does significantly affect sleep quality, even when artificial light sources are taken into account.
Using wrist monitors, the researchers studied sleep patterns in 98 people living in three indigenous communities in Argentina – each for one to two months. The places were intentionally different from each other: one municipality did not have access to electricity at all, the other had only limited access, the third was located in an urban environment and therefore had full access to electricity.
People in all three of these communities turned out to have very similar sleep cycle fluctuations, which were visibly associated with the Moon’s 29.5-day cycle. The length of sleep varied by 20 to 90 minutes, the time spent in bed by 30 to 80 minutes.
The shortest sleep time in all three places was clearly associated with the period of three to five days that preceded the full moon – and, conversely, the longest sleep always appeared on the nights before the new.
We sleep the least before the full moon
These results were slightly surprising for the study’s authors – they expected to find the least sleep on or shortly after full moon nights. However, according to Horacia de la Iglesia of the University of Washington, who conducted the research, the nights before the full moon proved to be more important, probably because they have most of the moonlight during the first half of the night.
On the contrary, it was not surprising that the effect of the lunar phases on sleep is weaker the more the place is electrified.
The researchers then verified these data from the countryside on students living in urban areas, in Seattle – and found the same patterns, although weaker, in them. “Taken together, these results strongly suggest that human sleep is synchronized with the lunar phases, regardless of ethnic and socio-cultural background and level of urbanization.” the scientists wrote in the journal Science Advances.
“We humans tend to believe that we have somehow mastered nature, and the use of artificial light is a great example of this,” added de la Iglesia. “But it turns out that there are forces of nature from which we cannot break away.”
This study does not show causality – that is, that the phases of the Moon are the direct cause of shorter sleep; she only found a strong correlation between the two phenomena. The authors of this research will try to find out whether the full moon or the new is really the main player in the coming years and subsequent studies.