As crucial as sleep is to many of our biological functions, its deep mechanisms are still mysterious to researchers. A new study has shown, that our sleep may be linked to the cycles of the moon. It’s all about the light. Or maybe more…
Accidents, mood swings, plant growth – or hair growth – natural disasters. Since the beginning of time, the Moon has been regularly blamed for various phenomena, real or imagined, that occur on Earth.
Researchers at the University of Washington reported that they have indeed observed a variation in sleep cycles during the 29.5-day lunar cycle. In the three to five days before the full moon, people in both rural and urban areas fall asleep about 30 minutes later on average and sleep 46 to 58 minutes less on average.
In the past, other studies had shown the impact of access to electricity on sleep. This effect was found in more recent work. Urban study participants went to bed later and slept less, on average than those who lived in rural areas without electricity. But all showed changes in their sleep cycles related to the moon’s cycle.
A light that disrupts sleep
And the researchers now believe their data are more reliable than what was published in the past. In fact, most of the old studies were based on statements, made by the participants in the studies. This time, the data was based on monitors attached to volunteers’ wrists.
“The phenomenon may be an adaptation that allowed our ancestors to enjoy a natural light source at night,” Leandro Casiraghi, a researcher at the University of Washington, said in a statement. In its rising phase and as we approach the full moon, the moon usually reaches the top of the sky after sunset. In its waning phase, the moon rises later and doesn’t illuminate the landscape until the middle of the night.
The light makes us fall asleep later.
Thus, the researchers drew a parallel to the influence of artificial light on our circadian clock. “It makes us fall asleep later. And it makes us sleep less because we don’t normally use artificial light to ‘advance’ the morning, at least not willingly. These are the same patterns we’ve observed with the phases of the moon” observes biology researcher Horacio de la Iglesia.
But a new question arises. For in the rural communities studied, the researchers also observed what they call a semi-lunar effect, a 15-day cycle around the phases of the new moon and full moon. The latter is harder to explain just from the effects of light. And it could be due, the researchers say, to gravitational phenomena yet to be determined.