Not sleeping well? It may be the moon’s fault — especially for men, study finds

Aside from ocean tides, the moon is known to influence other earthly objects and beings, including trees’ size, crabs’ reproductive activity and corals’ spawning events.

The effect lunar cycles have on people directly is less clear, but new evidence suggests the moon may play a role in how well we sleep, particularly for men.

At-home sleep recordings from more than 850 people in Sweden found that men experienced lower sleep efficiency and spent more time awake after initially falling asleep during the moon’s waxing phase — when the celestial body is on its way to becoming full, appearing bigger in the sky — compared to its waning phase, when the moon appears to shrink as it approaches the new moon cycle. Women, on the other hand, did not experience changes in sleep quality associated with lunar phases.

Researchers at Uppsala University in Sweden speculate male hormones and brain responsiveness to light could explain the gender disparities, though more study is needed to get a clearer picture of the components at play.

The findings held true even when the team adjusted for chronic sleep problems and obstructive sleep apnea. The study, published Sept. 9 in the journal Science of the Total Environment, adds to other research that has found slumber to be most disrupted during the full moon.

One possible explanation behind the moon’s ability to influence sleeping patterns is its power to reflect sunlight back to Earth.

As the moon approaches fullness (waxing phase), it becomes increasingly brighter as it bounces more sunlight off its surface. Waxing moons also rise during late afternoons or early evenings, meaning they sit high in the sky when it’s time for bed.

The extra night time light could explain why studies have found people tend to be more restless during waxing and full moon phases.

Waning moons behave differently. They tend to rise much later in the evening, meaning the light they give off peaks in the middle of the night when most people are already sleeping.

The lead author of a January study that found people go to sleep later and sleep for shorter periods of time in the days leading up to a full moon thinks there may be an evolutionary explanation.

“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,” Leandro Casiraghi, a University of Washington postdoctoral researcher, said in a statement.

Why do men appear to be more powerfully influenced by the moon?

Late nights spent scrolling through social media until your eyes tear up are testaments to the well-known fact that light at night can affect the quality of your sleep. That’s because it can hinder the release of the hormone melatonin in your body; natural levels are highest after the sun sets.

The researchers cite a study that found levels of melatonin, testosterone and the stress hormone cortisol in the blood of 20 male participants were lower during the full moon compared to the new moon — patterns that have been linked to disturbed sleep. Men have also been found to have more sensitive brain responses to specific intensities of blue and red light than women.

There is some hesitancy about blaming the moon’s light for poor sleep, however. Moonlight brightness, according to the Sleep Foundation, only has 7% of the strength of sunlight, and people are often exposed to more artificial light via technology than moonlight.

Another culprit: the moon’s gravitational pull.

Because the human body comprises mostly water, some experts have speculated the moon may have similar influences on people like it does on ocean tides. What’s more, water makes up about 60% of adult men’s bodies while it makes up about 50% of women’s, a difference that grows as we age. Studies on astronauts have also shown the loss of gravity affects their sleep.

But this theory is likely baseless. The Sleep Foundation says lunar influence on gravity is just about equal during the full and new moon, so sleep disturbances are likely not caused by gravity alone. Not to mention its effect on a single person is “minuscule,” the researchers said.

The new study was limited by the team’s inability to test for other “sleep-modifying factors,” including noise, temperature and bedtime use of screens. A total of 492 women and 360 men between 22-81 years old were included in the study. Participants wore special electrodes connected to a recorder as they slept.