In modern times, much research has focused on how artificial light sources disrupt our sleep and our health, due to the unnatural effects of lighting after sunset.
But to what extent is night light so unnatural? After all, humans have always been exposed to varying levels of light at night, due to the reflections of the rising and waning sunlight of the Moon, and this changing radiation stimulates us in ways that we are not fully aware of. , suggests new research.
“Moonlight is so bright to the human eye that it is entirely reasonable to imagine that, in the absence of other light sources, this night light source could have played a role in modulating activity and they are human nocturnes, ”said a team of researchers, led by senior author and neurobiologist Horacio of the University of Washington Church, explain in a new study.
“However, whether the Moon’s cycle can modulate human nocturnal activity and sleep remains a matter of controversy.”
To investigate the mystery, the researchers equipped more than 500 participants with wrist-based activity monitors, to track their sleep patterns, and conducted the experiment in very different locations.
First, 98 participants from the village of Toba-Qom, an indigenous community living in the Argentine province of Formosa, participated. Some of these rural participants in the experiment had no access to electricity, others had limited access to their homes, while a final contingent lived in an urban setting with full access to electricity.
In an independent experiment, the researchers tracked the sleep of 464 college students living in the Seattle area, a major, modernized city with all the electrified traps of post-industrial society.
Following participants ’sleep activity during the lunar month cycle, the researchers found that the same type of pattern could be seen during sleep and waking, regardless of where the volunteers lived.
“We see a clear lunar modulation of sleep, with decreased sleep and a later onset of sleep in the days before the full moon,” says the Church.
“While the effect is more robust in communities without access to electricity, the effect is present in communities with electricity, including students at the University of Washington.”
Although there was some variation between the results, in general, the data showed that sleep tends to start later and generally lasts a shorter time on nights leading to the full moon, when light the moon provided by the crescent moon is brighter in the hours after sunset.
Although the sample size studied here is not particularly large, and there is certainly more research that could be done here to expand these results, the same pattern was observed in two different populations living in separate countries and with different levels of ‘so different access to electricity among all the volunteers, tells us some important things, the team says.
“Together, these results strongly suggest that human sleep is synchronized with lunar phases regardless of ethnic and sociocultural background and level of urbanization,” the researchers write in their article.
As for what gives rise to these effects, researchers argue that the extended nocturnal activity stimulated by moonlight could be an evolutionary adaptation shifted from the time of pre-industrial human societies, with the ability to stay awake. and do more things under a bright full moon benefiting from all sorts of traditional customs that peoples without electricity still enjoy today.
“At certain times of the month, the Moon is an important source of light in the evening, and this would have been clearly evident to our ancestors thousands of years ago,” says the first author and sleep biologist Leandro Casiraghi.
According to interviews with Toba / Qom individuals, moonlit nights are still known for their high hunting and fishing activity, increased social events and intense sexual intercourse between men and women.
“While the true adaptive value of human activity during moonlit nights remains to be determined, our data seem to show that humans, in various environments, are more active and sleep less when light from the moon moon is available during the early hours of the night “. the researchers explain.
“This finding, in turn, suggests that the effect of electric light on modern humans may have taken advantage of an ancestral regulatory role of moonlight on sleep.”
The findings are reported in Scientific advances.