What does all that have to do with sleep?
The actual trigger for this blog were two scientific articles that were published this January. I would like to share the results even if they seem to just confirm what you have always felt intuitively.
It is also nice to get your intuition confirmed, especially if you are often accused to just imagine things – for instance, if you are very sensitive to the phases of the moon. No, your intuition is confirmed, at least by these two publications in the official journal of the American Association for the Advancement of Science.
The first one deals with a phenomenon familiar to all sexes: “Moonstruck sleep: Synchronization of human sleep with the moon cycle under field conditions“.
Researchers from the US and Argentina investigated sleep patterns in different groups: one the one hand in an indigenous community in Argentina, former hunter-gatherers (a little bit less than 100 participants). One of the groups had already adapted to urban life, including full electrification. The other two were living in villages, one of them with partial access to electrification (and the resulting artificial light) and the other with no access to electricity. Independently, the sleeping pattern of a group of „urban post-industrial“ undergraduate students were also investigated (almost 500 participants).
In all 4 groups, the length of sleep was shortest in the three to five days before the full moon, and this was independent of the availability of artificial light. Sleep of both groups of villagers (those without and those with just some electricity) also was influenced by the new moon. This could not be seen in the other two groups who had a much stronger exposure to artificial light (and maybe night life).
At least for the full moon this could also be an explanation for a higher risk of injury: with less sleep, we might be more vulnerable ?.
So don’t worry if you sleep worse before the full moon. You are not the only one on this planet.
The moon and the female cycle
In the same issue of the research journal, a group of German scientists together with one colleague each from Argentina and the US published the results of an investigation of the influence of the moon on the female cycle. The interesting approach here is that they looked individually at each woman’s cycle over decades, in one case for 32 years. You can find the publication here.
This study was limited to 22 ladies. Actually, I do not believe that there would be so many women who register details about their cycle for decades.
The project was triggered by the fact that there is quite some controversy in science whether human reproductive behavior is influenced by the moon or not. For many marine species and some terrestrial species, this has been clearly shown. A clear argument in favor of such an influence is that the average length of the female cycle is about as long as a synodic month (e.g. from one full moon to the next). Another argument in favor is the result of a number of earlier studies that found that women whose cycle is close to the 29,5 days of the moon cycle have the highest probability of getting pregnant. In these women, there was also a statistically significant relationship between the onset of menstruation and the full moon. On the other hand, several studies that did not focus on women with an about 29.5 days‘ cycle could not confirm these relationships.
It is also quite interesting that two large studies that analyzed between 250.000 and 500.000 births found that the probability of giving birth on a full moon day is 2 -3 % higher than on average, and similarly lower on a new moon day.
Still, much skepticism prevails in the scientific world whether the moon really has an influence on human behavior.
The researchers did not only look at the effect of the level of nocturnal light (quite luminous at the beginning of the night during a full moon, dark nights during a new moon), but also how the gravitational pull of the moon (which also follows its own periodic rhythm) plays a role.
Let me spare you the details (just this: in total, there are three different moon cycles measurable, of which two have their main influence on the gravitational pull). The highest gravitational force is exerted by the moon when it is closest to earth and at the same sun, moon and earth are in line, e.g. either on a full or on a new moon. This happens every 206 days (e.g. about every 7 months).
The study found that all three cycles have an influence on the start of bleeding, with the „usual“ cycle of 29,53 days showing the largest influence. This moon cycle also has the smallest variation – between 29,27 and 29,83 days.
Looking at the data in detail, the researchers found that the length of the cycle varied strongly both between different women and over the years for the same woman. For all women, the length of the cycle shortened with age. With one exception, all women had prolonged time frames where their period (and consequently with a two weeks‘ difference their ovulation) coincided with a new moon and more often a full moon (about 25 % of the years in total for all women under 35 years of age).
After the age of 35 years, „coordination“ lessened significantly. There was also one other important factor: night owls who were in a lot of artificial light during the nights would not fit the pattern, even if they were younger than 35 years of age.
It was also quite fascinating that all women who had given birth had experienced their last menstruation before becoming pregnant shortly before or after a new or a full moon.
Also the variations in the gravitational pull of the moon had an influence during certain time frames, but a little bit less than the effect of the amount of nocturnal light variation.
The strongest coordination between the moon’s cycle and the women’s cycle could always be found when the moon was closer to earth. These two above mentioned rhythms (full or new moon, closer to or farther away from earth) seem to superimpose.
It is not clear how we (or at least the females of the species) perceive the influence of the moons gravitational pull. There might be atmospheric effects (air pressure also varies with the moon cycle), magnetic influences (the moon influences the magnetic field of our planet – and it has been shown that certain animal species can feel this effect).
By the way, the influence is greater during winter than during summer. This is quite obvious concerning the effect of the nocturnal light, as the nights are shorter anyway. It is harder to explain for the effect of the gravitational pull.
Women have been aware of the effect of the moon already since the beginning of consciousness, I believe. It is nice that also modern science seems to catch up – having been skeptical for a long time.
As a short summary of both articles – should you have made it this far:
If someone tells you in the future that you are imagining that you can feel the moon, you have at least these two scientific studies on your side ?. Of course, if you are of a different sex than female, you also have at least one of the studies as a supportive argument – because the study on sleep was not limited to women.