Does the moon really affect our sleep?

This is a question that humans have grappled with throughout the ages. 

The lunar impact on biological rhythms is well documented in the natural world. Variations in tree diameter, reproductive patterns of crabs, spawning events in the Great Barrier Reef, and the nighttime activity of owl monkeys may all be affected by lunar cycles. The impact on humans is not so clear.

The full moon has captivated humanity for centuries, inspiring folklore, myths, and even affecting behaviours. Among the many claims surrounding the full moon's influence, one intriguing aspect is its alleged impact on sleep patterns. While scientific inquiry has often dismissed such beliefs as mere superstition, recent research suggests there might be more to the lunar-sleep connection than previously thought.

What do the studies say?

A study published in the journal "Current Biology" in 2013 conducted by researchers at the University of Basel in Switzerland shed light on this topic. The study monitored the sleep patterns of 33 volunteers in a sleep laboratory and found that participants exhibited reduced sleep quality and a decrease in deep sleep during the nights leading up to a full moon. Interestingly, participants also reported feeling less rested during these periods, despite spending the same amount of time in bed.

Further supporting these findings, a 2014 study published in the journal "Sleep Medicine" conducted by researchers from the University of Washington analyzed data from 319 participants. The study found that participants took an average of five minutes longer to fall asleep and slept for about 20 minutes less overall during the nights surrounding a full moon compared to other lunar phases.

One of the most fascinating studies looked at variations in sleep in both the time of sleep onset and the duration of sleep in urban and rural areas. They looked at indigenous communities in northern Argentina and college students in Seattle. What's interesting is that they found the same variations in sleep cycles regardless of an individuals access to electricity.

“We see a clear lunar modulation of sleep, with sleep decreasing and a later onset of sleep in the days preceding a full moon,” said de la Iglesia. “And although the effect is more robust in communities without access to electricity, the effect is present in communities with electricity, including undergraduates at the University of Washington.”

Using wrist monitors, the team tracked sleep patterns among 98 individuals living in three Toba-Qom Indigenous communities in the Argentine province of Formosa. The communities differed in their access to electricity during the study period: One rural community had no electricity access, a second rural community had only limited access to electricity — such as a single source of artificial light in dwellings — while a third community was located in an urban setting and had full access to electricity. For nearly three-quarters of the Toba-Qom participants, researchers collected sleep data for one to two whole lunar cycles.

Past studies by de la Iglesia’s team and other research groups have shown that access to electricity impacts sleep, which the researchers also saw in their study: Toba-Qom in the urban community went to bed later and slept less than rural participants with limited or no access to electricity.

But study participants in all three communities also showed the same sleep oscillations as the moon progressed through its 29.5-day cycle. Depending on the community, the total amount of sleep varied across the lunar cycle by an average of 46 to 58 minutes, and bedtimes seesawed by around 30 minutes. For all three communities, on average, people had the latest bedtimes and the shortest amount of sleep in the nights three to five days leading up to a full moon.

Why is the moon affecting our sleep?

“We hypothesize that the patterns we observed are an innate adaptation that allowed our ancestors to take advantage of this natural source of evening light that occurred at a specific time during the lunar cycle,” said lead author Leandro Casiraghi, a UW postdoctoral researcher in the Department of Biology. This is an interesting idea, given that we are natural hunter gatherers, and with the increased light from a full moon, it creates an excellent opportunity for hunting. 

Other theories include that the light from the moon impacts our circadian rhythm, with the increased light of the full moon increasing our cortisol level and causing us to stay awake longer and sleep less at night. Another hypothesis is the moon's electric charge can influence the Earth's electromagnetic field, with new research showing humans are sensitive to to low-level geomagnetic variations. Other geomagnetic events (such as geomagnetic storms and the recent aurora borealis lights) that produce geomagnetic fluctuations comparable with the moon’s impact have been connected to a range of health effects, including headaches, changes in blood pressure and blood flow, heart rate variability, and even heart attacks.

The idea that the moon’s gravitational pull affects human health is based on the fact that the human body is mostly water, and lunar gravity has a noticeable effect on ocean tides. Critics of this theory cite that the gravitational pull of the moon is extraordinarily small in humans. Researchers estimate that the impact of lunar tides on a person measures less than one-millionth of the size of an atom.

What do you think?

Have you ever noticed a difference in your sleep from the lunar cycles. I've noticed for myself, that once I started paying attention to the lunar cycles I would notice that leading up to the full moon I would struggle to sleep. I felt energized even though I was tired, and would spend more time lying awake at night. Through this realization it has helped reduce the stress of not sleeping, as there appears to be very real reasons for why the lunar cycles are having an impact, even if we don't know exactly why.

Sometimes when we're experiencing insomnia, it is completely out of our hands. Knowing that can help us mitigate the days where we haven't got the rest we need, take it a little easier on ourselves and marvel at this incredible world we live in.