Debunked: Study shows link between menstrual cycle and the moon

deirdre

Senior Member.
anecdotal but ive lived with women who i've synced with. and ive lived with women who i didn't sync with.

i've also worked with women who i've synced with. and worked with women who i didn't sync with.

i've also synced with one sister in law who i almost never saw, and didnt sync with other sisters-in-law who i spent more time with.

(i dont know anyone, even amongst my hippy dippy friends, who paid attention to moon cycles..so i have no anecdotal input on that one)

I thought "They do if they want their periods to synchronize" was meant as playful.
i think the whole thread is playful.

edit add: oh and just so ya know... you can change your heavy flow days with like 2 weeks notice if youre gonna be traveling or going to a festival or concert or wedding or something. i imagine that likely throws off sync days too, unless your roomates or workmates are going to the same festivals etc.
 

NoParty

Senior Member.
i think the whole thread is playful.
As a wildlife aficionado, I'm genuinely interested in why/how, in nature, so many animals give
birth at the same time (the "why" is often assumed to be that predators can only pick off so many,
and some young will survive (oh, and surviving winter "reproductive seasonality")...
but that's not for sure, and still doesn't address the "how").
https://www.sciencedaily.com/releases/2018/05/180507111834.htm
https://onlinelibrary.wiley.com/doi/10.1111/brv.12646

Glad I accurately interpreted one of your posts. :)
 
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deirdre

Senior Member.
As a wildlife aficionado, I'm genuinely interested in why/how, in nature, so many animals give
birth at the same time (the "why" is often assumed to be that predators can only pick off so many,
and some young will survive (oh, and surviving winter)...but that's not for sure, and still doesn't address the "how").

Glad I accurately interpreted one of your posts. :)
i dont think animals go into heat every 28 days. probably depends on the animal species to look into. i know cats "generally" go into heat at the same times of year, and since its not all year the male cats are on that quick! :) if y'all get impregnated in the same week or two then your babies will come around the same time.
 

Rory

Senior Member.
I would watch bison in Yellowstone, virtually all give birth at the same time - which means same conception time, which suggests some cycle sync.

When you said "they gave birth at the same time, suggesting some cycle sync" it seemed like you were saying they gave birth on the same day (or very close to it). But that doesn't seem to be the case, according to this:

https://www.nps.gov/articles/bison-bellows-2-11-16.htm

Which says that 80% of bison are born in April or May (a period of almost 9 weeks) and that the bison birthing season is generally from mid-April to mid-July.

Which would suggest vastly different conception times and no cycle sync, if I'm reading it right.

Why they're mosty born during those months, though, is explained like this:

Some scientists think birth synchrony occurs in bison due to strong seasonal limitations on food availability and quality, so that females enter estrus as a group depending on when their physical condition recovers from a long period of food stress that they all go through together. In this case, when green grass is limited to only a relatively short period of time, birth synchrony would be expected to be more focused than when green grass is available for a longer period of time. This reason could also explain why birth synchrony occurs just prior to peak green grass availability, when the mother would have access to the best food of the year, and thereby optimize her milk production following birth, thus benefiting her calf nutrition and growth.

Another consideration is that birth synchrony occurs in order to increase the chance of survival for individual newborn wildlife in the presence of predators. Under this scenario, an individual calf would potentially have a higher chance of survival if it was born amongst a larger group of calves, than if it was born alone, say in the face of wolf or bear predation. Birth synchrony can also be explained amongst herding animals like bison, wherein a larger number of simultaneously ovulating females makes it harder for any one male to monopolize breeding – and thus competition amongst males is stronger and paternity is distributed more widely across the total male population, thereby increasing the overall genetic fitness of the population.
 
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deirdre

Senior Member.
Which says that 80% of bison are born in April or May (a period of almost 9 weeks)
or 6 weeks and 3 days if we're saying "mid-april" and may. i think that counts as "at the same time". esp. since bison of the same group are likely closer together since they all have access to the same food sources. and vs. humans who give birth all year.

the real question is do bison go into estrus on the full moon? :)
 

NoParty

Senior Member.
When you said "they gave birth at the same time, suggesting some cycle sync" it seemed like you were saying they gave birth on the same day (or very close to it). But that doesn't seem to be the case, according to this:

https://www.nps.gov/articles/bison-bellows-2-11-16.htm
I wasn't suggesting the same day, though that would be quite a trick!

I don't know if many people witness a large number of bison births, to know...I just know that by the
time I get there in summer, there's a ton of little "red dogs" that look to be very, very similar in age.
 

Mendel

Senior Member.
Sunlight has various effects on the human body. I'm not really surprised that moonlight could have some effect as well. I'd not suspect gravity.

I'm also not surprised that the substances in an artificial perfume have hormone-like effects (that's re: the laundry detergent story).
 

Rory

Senior Member.
I'm not really surprised that moonlight could have some effect [on the human body].

Moonlight has some effect on the human body, but Strassmann (1997) found no evidence that moonlight had any effect on the human menstrual cycle.
 

Mendel

Senior Member.
Moonlight has some effect on the human body, but Strassmann (1997) found no evidence that moonlight had any effect on the human menstrual cycle.
Well, Strassmann didn't find any effect at all, so with that data, she couldn't possibly have answered the question if moonlight was causing it.
And it puts forward the idea that some women sometimes appear to synch with the full or new moon, based on patterns such as these:
The human body is complex, the reproductive cycle is complex, it's not surprising that some effects might not occur to everyone or at all times. I can easily handwave Strassmann away by mumbling "genetic predisposition" or something like that, but to handwave these patterns away, I'd better find manipulated or at least cherry-picked data.
3. There is no known mechanism to explain why such a thing would occur, and why it would occur in humans but not in other mammals.
And that's why I am bringing up light.

I don't think we have any data on how gravity affects human hormones; if you were looking for that, you might want to compare people from Denver with people from a comparative city closer to sea level, adjust for a bunch of confounding variables, etc. We know that microgravity has effects on the human skeletal and muscular systems; with women in space now, maybe we also have data on how microgravity affects reproductive cycles, but I suspect the astronauts simply suppress theirs?

But with light, we know that sunlight affects diurnal patterns, including hormones and everything, so there's at least an anlogous mechanism to what we're looking for. If we could now find that these "synchronous" phases correlate with exposure to moonlight, that'd be a strong clue.

It could also be a second-order effect, like animals howling at the moon or otherwise being differently active depending on the moonlight, and that affecting humans. Like, if our ancestors heard wolves howling, they might be more stressed, and then we have a connection to hormones again; it would still need to be fleshed out and investigated, though.


There's no reason to assume that if there is a link (sometimes/for some women), it's caused just by the moon being there (astrology) or its gravity (bunk science); but that's no proof that no link exists.

P.S.: We've seen that most mammals don't have cycle lengths that are anywhere near the moon period, and since the moon effect seems to be small, it's not surprising the cycles wouldn't sync up. Orangutans have 29 days, so maybe you could find some of these synced up -- or maybe not.
 
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FatPhil

Active Member
And that's why I am bringing up light.

Not a bad place to look, certainly. A quick scratch around found several studies that seem to have a confirmatory nature, such as:

E.M. Dewan, M.F. Menkin and J. Rock, "Effect of Photic Stimulation on the Human Menstrual Cycle," Photochemistry and Photobiology 28 (1978), 581-585.

-- https://pubmed.ncbi.nlm.nih.gov/674392/

Orangutans might not provide as reliable data, as they do nurse for many years and don't bear new young during that time, so there's a good chance that a fair slice of a wild population might not be following any kind of estrus cycle. And of course captive populations could also have almost everything perturbed. A wander around the internets seemed to show that belief in synchrony isn't unusual in the field, but mostly focussed on a pheremonal explanation rather than an exogenous one. However, biology is *far* from my field (but one I've attempted to self-teach in recent years), and I really can't judge the reliability of any of the sources I encounter.

It's an interesting field, as I mentioned above, it would be nice for some more definitive answers to be arrived at.
 

Rory

Senior Member.
Interesting words, you guys, on an interesting subject. Mainly for me I'm thinking about the most recent paper I posted, and looking specifically at that rather than other ideas, since that's the only source in all my investigations on the subject that's shown even a little bit of promise.

Also:

It could also be a second-order effect, like animals howling at the moon...

But according to animals.howstuffworks.com/mammals/wolves-howling-at-moon.htm:

1619053444420.png
 
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Rory

Senior Member.
E.M. Dewan, M.F. Menkin and J. Rock, "Effect of Photic Stimulation on the Human Menstrual Cycle," Photochemistry and Photobiology 28 (1978), 581-585.

Tricky to know what to make of that study. Here's their table of results:

1619055947557.png
Source: https://sci-hub.se/https://doi.org/10.1111/j.1751-1097.1978.tb07649.x

I would say more data required. There's a lot of potential there for random noise.

(Also, they say "normal cycle length" is 29 days, whereas that's actually the average - "normal" is anywhere from about 21 to 40 days.)
 
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deirdre

Senior Member.
dogs can see you better during a full moon, so its harder to escape.


hmmm. ok maybe its not that :)
bold added for emphasis:
Article:
“While the results of our retrospective study indicate that there is an increased likelihood of emergency room visits on the days surrounding a full moon, it is difficult to interpret the clinical significance of these findings,” Wells writes. “Many studies have investigated the effect of the moon on human nature, behavior and various medical problems, with evidence both supporting and refuting the effect.”

Wells cautions that, while the percentage of increase in emergencies during fuller moon days may be large, the correlation to an actual number of animals is actually quite low. The university’s Veterinary Medical Center’s critical care unit may see a few cats and a few dogs on a night without a full moon, and data showed an increase by about one cat or one dog during fuller moon days.

In addition, data did not indicate that there was an increase in aggressive behavior in pets during a full moon. For example, there was not a measurable increase in injuries from dogs acting aggressively.
 

DasKleineTeilchen

Active Member
But with light, we know that sunlight affects diurnal patterns, including hormones and everything, so there's at least an anlogous mechanism to what we're looking for. If we could now find that these "synchronous" phases correlate with exposure to moonlight, that'd be a strong clue
heard about that one before; how is that gonna work with moonlight?!? most people sleep at night. or are at least in closed rooms, like their house/flat. what about in winter? full-moon is much lower in winter. what about cloud-cover? rainy weather? what then about animals in the open? do they have a hormone-correlation with the moon? people and animals in bright cities, the ambient light in cities alone overshines every moonlight. etcetera.
 
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FatPhil

Active Member
heard about that one before; how is that gonna work with moonlight?!? most people sleep at night. or are at least in closed rooms, like their house/flat. what about in winter? full-moon is much lower in winter. what about cloud-cover? rainy weather? what then about animals in the open? do they have a hormone-correlation with the moon? people and animals in bright cities, the ambient light in cities alone overshines every moonlight. etcetera.

Artificial lighting certainly is interfering with the breeding behaviour of many species. The most well-known cases would probably be turtles.

-- https://www.conserveturtles.org/information-sea-turtles-threats-artificial-lighting/

With the obvious rider that turtles are cladistically a very long way from the primates we started the thread on.
 

FatPhil

Active Member
I would say more data required. There's a lot of potential there for random noise.

Absolutely. I'd like to see data that's so clear that one can also conclude whether it's easier to artificially shorten an intrinsic preferred cycle length than it is to lengthen one or not.

There are really trivial mechanisms for shortening cycles, but lengthening is more complex. From a mathematical modelling perspective, but one informed by biological mechanisms. A classic example being fireflies:
-- DOI:10.1007/BF00164052

There's a simulation of such simple models in JS here: https://ncase.me/fireflies/
 

Mendel

Senior Member.
heard about that one before; how is that gonna work with moonlight?!? most people sleep at night. or are at least in closed rooms, like their house/flat. what about in winter? full-moon is much lower in winter. what about cloud-cover? rainy weather? what then about animals in the open? do they have a hormone-correlation with the moon? people and animals in bright cities, the ambient light in cities alone overshines every moonlight. etcetera.
All potential reasons why the effect only shows up in some people and not in others.
Btw, most cloud cover doesn't really affect the brightness of a full moon night much.
 

Rory

Senior Member.
The key study in questions of moonlight and menstruation is Strassmann's, which looked at women who lived much of their lives outside and used no artificial lighting. She found no evidence of synchronicity with either the moon or each other.

There are plenty of studies that claim to show correlations, but when you read good analyses of these you pretty much always find those studies are flawed. So it's definitely best to look into them properly rather than just taking the abstracts or conclusions at their word and pasting the link. Cutler's oft-cited study is a great example of this. Generally they seem to be plagued by small sample sizes and lazy statistical analysis.

Hopefully soon I'll get around to the study in question. :)
 

Rory

Senior Member.
Okay, let's have a look at the paper I posted the other week, which claims to have shown that "Women temporarily synchronize their menstrual cycles with the luminance and gravimetric cycles of the Moon".

Introduction and 'facts'

1. “In many marine species and some terrestrial species, reproductive behavior is synchronized with a particular phase of the lunar cycle (often full or new moon).”

Seems reasonable. Nine references cited. Though I notice the ninth one is a study I’ve come across before claiming a connection between the lunar cycle and birth rate in cows. It used a very small sample size (428 cases) whereas a much larger study involving a few million births showed no pattern. I wrote to one of the authors of this study a year or two ago and pointed out the flaws in their methodology and conclusion, but they stuck to what they believed their own data showed them rather than the data from the largescale study (understandably).

2. “It is of interest that the human menstrual cycle has a period close to that of the lunar cycle.”

I mean, not really. Number one “the human menstrual cycle” has a ‘normal’ period of between 21 and 38-40 days, whereas the lunar cycle is much less variable (+/- ~0.3 days) so there’s not really a similarity. The average menstrual cycle is around 29 days, which is close to the average lunar cycle of 29.53 days – but so what? If the average human male is 5 feet 9 and the average horse is 5 feet 10, does that suggest the two are somehow related?

3. “Several older studies report a relation between the [two] cycles.”

Some bad studies do report a relation. As discussed above, Cutler’s studies being the prime example, and these are cited repeatedly throughout the paper. When I messaged Helfrich-Förster about these studies she admitted that she hadn’t looked into them closely, which – when coupled with the dubious citation noted in point 1 – doesn’t bode well for the other references used. Cutler’s studies are excellent examples of terrible science and, to her credit, Helfrich-Förster agreed with the issues we raised here.

Furthermore, the biggest and best studies – the Clue study, for example – find zero relation.

4. “In these studies, about 28% of reproductively mature women showed a cycle length of 29.5 ± 1 days. Among populations of women selected for a cycle length of 29.5 ± 1 days, a significant pattern of menses onset at full moon emerged. Each of these studies comprised >300 women, and the tests were performed in different years and seasons.”

Figures from Cutler, therefore irrelevant and not a good way to start your paper. “>300 women” is an insignificant number and it’s surprising that academics with a good understanding of statistical analysis wouldn't pick up on that. Far too small a sample size to detect a “significant pattern” – which there wasn’t in those studies in any case.

5. “Significant correlations also appear to exist between birth rate and moon phase.”

Absolutely untrue. Again, some small scale and methodologically dubious studies are cited, whereas the two largest studies – that of Caton and Wheatley (2002) and the one I did here (together comprising 155 million births) – found no correlation whatsoever.

(This paper seems to have primarily taken as ‘proof’ for the “significant correlations” the three studies done by Menaker and Menaker from the 50s and 60s. None of the studies agree with one another, and the deviation from the mean was tiny (1-3%) – which, of course, is about what we would expect given the randomness of nature.)

6. “Effects of gravity might account for the fact that synchrony of sleep onset and sleep duration with the lunar cycle has been observed in college students living in the light-polluted city of Seattle, where the Moon’s luminance cycle is scarcely perceivable.” (from later on in the paper)

Maybe. Not sure. https://advances.sciencemag.org/content/7/5/eabe0465

7. “Bipolar mood cycles have been reported to oscillate in synchrony with either the full moon phase or the new moon phase of the Moon’s luminance cycle.”

An interesting paper here related to that: https://www.nature.com/articles/mp2016263. But I haven't looked into it, and it's probably too new an idea with too little research done to confirm or deny.

8. “Several studies including ours have shown that night light shortens the length of the menstrual cycle.”

I don’t know about the reliability of this claim. FatPhil above posted a link to a study that claimed to show that night light regulated the length of the menstrual cycle (though for some it lengthened). Very possible that the light was applied in a different manner, though.

9. “The scientific community generally remains skeptical of reports of lunar influence on human biology.”

I believe the scientific community – or, at least, those who have an interest and have looked into it properly – would go further than that, and state with confidence that there is no reason to believe that the moon has an influence on human biology, and that all evidence points to this not being the case.

Still, it’s always good to be open to the possibility of being proven wrong in something like this – but, unfortunately, this has not been a good opening for the paper.

Methodology

1. “We examined the course of menstrual cycles in 22 individuals who kept long-term records of menses onsets. This approach allowed for the possibilities that lunar influence might be present intermittently and in different forms over the females’ life. Furthermore, in our study, we tested the Moon’s gravitational influences on menses onsets, in addition to its nocturnal light effects. To our knowledge, this approach to the evaluation of such long-term data has not been used previously.”

Yes. Excellent idea. An unfortunately small sample size, but it was difficult for them to find sufficient women who had kept long-term records.

2. “[Some basic facts about the lunar cycle; and] when the Moon is at its perigee and simultaneously in Moon-Sun-Earth syzygy, the gravitational forces on Earth are very high.”

The gravitational forces exerted on an individual human, however, are tiny: my laptop is probably applying more gravity to my body than the moon is, no matter where it might be situated in relation to Earth.

3. "We found that all three lunar cycles—the synodic, the anomalistic, and, to a lesser degree, the tropical month—affect menses onset.”

Steady on. That seems a bit like jumping to conclusions – especially with such a small sample size, and with such a shaky beginning. Let’s look at the data first…

4. “Nocturnal moonlight appears to be the strongest zeitgeber through which the Moon exerts its influence. We hypothesize that in ancient times, human reproductive behavior was synchronous with the Moon but that our modern lifestyle, notably our increasing exposure to artificial light, has changed this relation.”

Interestingly, that’s the get-out clause that moon-loving women use when I point out that their belief in the menstruation-lunar connection is flawed (even, usually, by their own data and experience). But Strassmann’s studies showed no lunar connection in people who lived as “in ancient times” and had no exposure to artificial light (Strassmann curiously not cited here).

5. “To determine whether menses onsets were ever synchronous with the lunar cycle, we analyzed the relation of menses onsets to the full moon and the new moon, to minimum and maximum lunar standstills, and to lunar perigees and apogees for each individual.”

Cool. Now we’re getting to the data. And I do like their approach: take the onset dates over the course of a long period of time and plot them against what the actual moon was actually doing. It’s a novel approach that should reveal something other larger scale studies potentially miss in bunching huge numbers of women of all ages together.

Data

What I find most interesting to look at are the charts that show exactly when a woman began her period plotted against what the moon was doing at the time. For example, for 6 of their 22 subjects:

chart1.jpg

This shows, for example, that Subject 1 had prolonged timespans where her menstrual cycles were approximately 29.5 days in length several times in her life: in 1979/80 (aged ~22); in 1998 (~41); and between 1999 and 2003 (aged ~42-46). These are designated by the yellow and blue arrows (there are also occurrences in 1991, 1996, and 2010, but these seems a little short).

The apparent significance here is that not only were these incidences of regular cycle lengths of the same duration as the lunar cycle, but that they only occurred on the full or new moon, and at no other times in the lunar cycle - ie, the vertical straightish lines formed by the black dots are uniquely aligned to either the full or new moon.

Looking at four of the other five subjects, the same is also claimed. Subjects 2 and 3 have long periods of being 'aligned' with the full moon (ages 19-27 and 27-31 respectively), and a few proposed shorter periods in later life, while Subjects 4 and 5 have less clear 'patterns' and shorter timespans of 'alignment' - though what clusters they do have, again, seem only in alignment with the full/new moon and don't occur in other parts of the synodic lunar month. Subject 6, however, doesn't seem to exhibit any signs of 'synchronization'.

Charts for 8 more subjects are provided (those who kept records for several years before 35 years of age):

chart2.jpg
chart3.jpg

In the authors' own words "Subjects 8 and 11 [...] did not show any synchronization to the synodic lunar month", while it appears to me that Subject 9 showed a decent alignment with the full moon aged 26-27 and 26-37; Subject 7 around age 28; and Subject 15 around age 16. The rest have claimed periods of alignments - as pointed out by the arrows - but they seem quite weak.

For the remaining 8 of the 22 subjects, either their charts weren't included because they didn't exhibit any semblance of conforming to the pattern or I'm completely missing mention of them, despite looking through the paper several times (not impossible).

Therefore I guess what we have is 6 subjects who were 'aligned' with the full/new moon for prolonged periods of time (and not with any other day of the lunar month); 5 who could be claimed to have some sort of 'alignment' (if you squint a bit); 3 who didn't; and probably another 8 who didn't either.

I guess the crux is: how can we explain why, when these women did have prolonged periods of 29.5-day menstrual cycles, did they only ever correspond with a full or new moon? Is "chance" or "small sample size" a satisfying enough answer? I'm not sure it is.

A note

It strikes me that, were the onset dates plotted against different cycles lengths - eg, 26 days or 32 days - we would also see prolonged periods of "vertical black dots". This seems that it would be true given the large number of uniformally-sloped diagonal lines in the charts above (indicating prolonged periods of cycles longer or shorter than 29.5 days). According to the paper, however:

“A systematic test with different hypothetical lunar cycle lengths ranging from 27 to 32 days showed that the significant results for the a priori hypothesis of synchronization with the full/new moon did not emerge by chance.”

I'm surprised by this. But will have to think about it more.

The tropical cycle

They felt this had less of an effect than the synodic cycle, so I won't look at that.

Saros #137 eclipses

The paper states that:

"There were four episodes, in the second halves of 1961, 1979, 1997, and 2015, in which seven of nine women’s menstrual cycles oscillated in synchrony with the synodic month (blue shaded areas in the charts above). The 18-year interval between these years corresponds to the period of a cycle of lunar eclipses that occur in September at those years, called Saros series #137. Saros #137 eclipses are distinguished by the contemporaneous occurrence of perigees that are unusually close to Earth. The conjunction of these two events may have augmented the Moon’s strength as a zeitgeber."

And I'm not sure what to think about that.

Lost focus

Either I lost focus after this or the paper did. There was a claim that menstrual cycles synced with the gravimetric lunar cycle, but I couldn't see it in either the data or the charts, so maybe you can:

chart4.jpg

Yellow diagonal lines = apogee and grey = perigee (green vertical lines = maximum lunar standstill and pink = minimum).

Conclusions

1. “The synodic lunar cycle alone does not appear to be a strong zeitgeber because synchronization occurred only intermittently and, during any particular period, the women differed from each other in the courses of their menstrual cycles and in the timing of synodic synchronization."

I'm a little confused by this as I thought this was the whole point: that the synodic lunar cycle does appear to be a zeitgeber. Indeed, the paper itself says: "We found that all three lunar cycles—the synodic, the anomalistic, and, to a lesser degree, the tropical month—affect menses onset. Nocturnal moonlight appears to be the strongest zeitgeber through which the Moon exerts its influence, but the gravitational forces of the Moon clearly contribute."

Perhaps the key to understanding is in the use of the word "strong" - and this is where the proposed effect of the Saros #137 eclipses is added in: "The conjunction of these two events [full/new moon and Saros #137 eclipse] may have augmented the Moon’s strength as a zeitgeber."

2. “Our principal results are consistent with the results of earlier studies on menstrual, mood, and sleep-wake cycles, which revealed that humans are sensitive to the Moon’s luminance cycle and even synchronize with it. Earlier studies showed that about 22 to 32% of reproductive age women experienced menstrual cycles with 29.5-day cycle lengths and onsets of menses around the time of the full moon.”

Primarily citing the debunked Cutler study here, which simultaneously renders the paragraph irrelevant; makes me sceptical of the quality of the other “earlier studies” cited; and further damages the credibility of the paper as a whole.

3. "While [earlier] studies found onsets of women’s menses that occurred around the time of the full moon consistent with the hypothesis that ovulation happened predominantly at the new moon, we found that onsets of menses also occurred around the time of new moon. Thus, something may have changed over the decades that followed earlier studies.”

That’s a staggering hypothesis to propose, and again incredibly damaging to credibility. Couldn’t it simply be that the earlier studies were bunk? Which is very clearly the case. No need to think that "something may have changed" since the early-1980s that would affect women's menstrual cycles.

4. "We show here that menstrual cycles were intermittently synchronous with the luminescence and/or gravimetric cycles of the Moon, strongly suggesting that both cycles influence reproduction in humans. On its own, each type of lunar cycle appears to be a weak zeitgeber. However, both appear to cooperate, leading to the best synchrony between lunar and menstrual rhythms when the Moon was close to Earth."

Again, if that's the case - that the intermittent synchronicity has been shown - I'm not really seeing it. Maybe someone else can point out the places in the charts where the combination of the luminescence and gravimetric cycles has been shown to affect the onset of menstrual cycles. Mainly, it just seems that they included the data for Subject 5:

chart5.jpg

This shows some quite prolonged periods of aligning with the gravimetric cycle, and some prolonged periods that didn't. Presumably this was the best example of the 22, since it was the main one featured; and of the other 5 that were included in these charts, the correlation seemed quite weak:

chart6.jpg

In conclusion, that's my first cursory glance over the paper. The patterns generated by 6 of the women's records - and, to a lesser extent, possibly another 5 (therefore up to 50% of the sample size) - are quite striking and intriguing: it seems that if random chance were the explanation we ought to be seeing more of those "vertical black lines" at different times of the lunar cycle, and I think the probability of only finding those lines, across multiple subjects, on either full or new moon is pretty slim. So there may be something in it after all. But with so few records to look at, it's impossible to draw any conclusions, other than to say: gee, it would be interesting to look at the data of, say, a few hundred women and see if more patterns like this emerge.

If anything's been "shown", though, I can't see it. And the use of bad previous studies - while ignoring good ones - doesn't bode well for the credibility of the potential conclusions.

Anyway, maybe someone can fine tune, correct, build on, and explain the above. I'm a little bit lost with it right now, after a half-decent start. Probably something to do with the moon... :)
 
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Mendel

Senior Member.
First thoughts:
a) Why are the blue and yellow lines wavy and not in sync?
b) why aren't there lines that delimit 7.4 day intervals around the new and full moons?
c) the light theory does not really explain new moon synchrony well
d) the gravimetric graphs look like "if you draw enough lines, something will stand out", that's not good evidence
e) I don't think I understand the Saros cycle well enough, does it have to do with the brightness of the moon?
f) The apparent Moon diameter scales with the distance from Earth; it's area scales with the square of the distance; the attenuation of light scales with the square of the distance; so if the moon gets closer by factor of x (say 0.925 as closest distance/average distance), it gets 37% brighter (+67% from darkest to brightest).
The distance to the sun adds another 14% on top of that (darkest to brightest), so I think the astronomical strength of the moonlight (not regarding weather) goes from 100% (Earth farthest from sun and moon) to 191% (closest to both)[(405/356)^4*(152/147)^4]. [Sunspots cause 0.1% fluctuation and don't matter.]
g) I looked over your OP again, and I wonder why you excluded weekends; wouldn't weekend births be mostly unscheduled, and thus be better data for this purpose?
h) Is the data from the Helfrich-Förster paper available?
i) subject 3 has prolongued periods of half-moon synchronicity
j) subject 7 has 2 periods of half-moon synchronicity
k) subject 8 has one period, only this subject has a grey arrow pointing it out
For the remaining 8 of the 22 subjects, either their charts weren't included because they didn't exhibit any semblance of conforming to the pattern or I'm completely missing mention of them, despite looking through the paper several times (not impossible).
l) you posted the data for subjects 10, 16, 17, 18, 22 in the gravimetric charts
m) how were the subjects selected for inclusion in the study? [important!]
 
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Mendel

Senior Member.
m) how were the subjects selected for inclusion in the study? [important!]
Self-selected. Hmm.
Theory: Few women who don't see moon synchrony in their menses data keep the data around for more than 5 years. ;)
(There's no reason to exclude the shorter records.)
 

Rory

Senior Member.
a) Why are the blue and yellow lines wavy and not in sync?

I would guess that's because of the variation in length of the lunar cycle: ie, between 29.18 and 29.93 days.

b) why aren't there lines that delimit 7.4 day intervals around the new and full moons?

I'm not sure why there would be (any 'interval' is really an artifical one anyway).

e) I don't think I understand the Saros cycle well enough, does it have to do with the brightness of the moon?

I think for them it has to do with both increased light and increased gravity:

"Light blue shaded areas indicate years of Saros #137, which were characterized by high luminance and high gravitational influence of the Moon during periods when Sun-Earth-Moon syzygies coincided with perigees in which the Moon was exceptionally close to Earth."

Though I'm not 100% clear whether they understand that the Moon's gravitational effect on humans is insignificant (ie, less effect than what we stand next to).

g) I looked over your OP again, and I wonder why you excluded weekends; wouldn't weekend births be mostly unscheduled, and thus be better data for this purpose?

The OP for the other thread? Weekends are significantly lower than weekdays (and Tuesdays somewhat higher) so they would skew the results. But I think in later posts and analyses I included weekends, Tuesdays, holidays, 13ths, etc but weighted for them. Which was quite complex and time-consuming - and whichever way I looked at it, no patterns or anomalies.

h) Is the data from the Helfrich-Förster paper available?

I just asked that in an email. There is some supplementary material available at the original link too, but it looks like the full data is an 'on request' thing.

i) subject 3 has prolongued periods of half-moon synchronicity

True. I'm seeing 1994 and 1998. Didn't notice them before.

j) subject 7 has 2 periods of half-moon synchronicity

I see one in 1960/61. Which is the other one?

k) subject 8 has one period, only this subject has a grey arrow pointing it out

Yes, I guess if those 4/5 cycles were on a full/new moon they would have been counted as supporting the theory. (The two red asterisks for her denote births, so unfortunately no chance for further data during that period, while the grey arrow doesn't seem to be explained.)

Well spotted on those.

l) you posted the data for subjects 10, 16, 17, 18, 22 in the gravimetric charts

True. But those charts are based on 27.32-day cycles, so they don't show where their start dates fell in relation to full/new moon.

m) how were the subjects selected for inclusion in the study? [important!]

Agreed. My hunch is that they took everyone they could find, and that it's harder than we might think to locate such records and data. Though I bet if I messaged all my female friends and they passed it on to all theirs we could come across some record-keepers.

Self-selected. Hmm.

Ah yes, so they did use all they could get (with records of longer than 5 years). I guess the question with the "self-selecting" is: did they know the study was about lunar synchrony, and therefore those who believed they had some degree of synchrony may be more likely to respond?

If not, however, it seems reasonable enough.

Thanks for taking the time to look through and add to. :)
 
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Mendel

Senior Member.
I see one in 1960/61. Which is the other one?
1952 is the other half-moon synchronicity period for subject 7

Ah yes, so they did use all they could get (with records of longer than 5 years). I guess the question with the "self-selecting" is: did they know the study was about lunar synchrony, and therefore those who believed they had some degree of synchrony may be more likely to respond?
I'm more thinking along the line that women who have heard of the "moon effect" and experienced it are more likely to keep recording this data. But of course that's an unsupported conjecture at this point.
 

Rory

Senior Member.
Clue would have access to potentially hundreds of thousands of semi-long term records (up to about 8 years in length).

I'll drop their data analyst person an email.
 

Rory

Senior Member.
I'm more thinking along the line that women who have heard of the "moon effect" and experienced it are more likely to keep recording this data. But of course that's an unsupported conjecture at this point.

With a sample size of one, I can safely say this isn't always the case: she has a regular 25-day, so knows she could never be in sync with the moon, but has kept a record for a number of years for a variety of reasons, such as: it's good to know; keeping track of one's health and body; being aware of any changes; being prepared on night's out, holidays, etc; and now because it's on an app (did keep diary records before) it's easy and stats are generated automatically.

I do still think it's an excellent point though, and find it striking that the best fitting subject (#2) is synced right from the start.

Did she notice that she always bled around the full moon and then decided the keep a record? Did others maybe start keeping records but then stop when they found no degree of synchrony?

The self-selecting nature can't be ignored: though, to balance that out, she's the only one of the 22 that would fit that criteria, and the vast majority of the data clearly doesn't have any degree of synchrony with the lunar cycle, yet they kept recording - probably for reasons such as those mentioned above.
 

deirdre

Senior Member.
yet they kept recording - probably for reasons such as those mentioned above.
if youre not on contraceptives, as the paper stated as criteria, the biggest reason is for using the timing method for birth control. whether that is a myth as well, i dont know. it always worked for me thank god!
 

Rory

Senior Member.
the biggest reason is for using the timing method for birth control. whether that is a myth as well, i dont know.

Nah, that's a real thing - though a woman can still get pregnant any day of the cycle, including on her period (chance quoted as "close to zero" though). Lots of graphs like this one online:

1620258593893.png
 

FatPhil

Active Member
Nah, that's a real thing - though a woman can still get pregnant any day of the cycle, including on her period (chance quoted as "close to zero" though). Lots of graphs like this one online:

1620258593893.png

The rhythm method is often maligned, but it's not much worse than most of the other methods that require some vague competency at doing it right. E.g.:
-- https://www.plannedparenthood.org/learn/birth-control/condom/how-effective-are-condoms
(Note, the <1% level on the cycle chart that the curves stay at for a fair chunk of the cycle and these 2%/15% numbers are not directly comparible, they're measuring different things. IIRC cycle awareness gets a score of ~80-85% in comparison to condoms' 85%. As I say - it's cheap and easy to malign the rhythm method, but in reality, common alternatives can be almost as risky.)
 

Rory

Senior Member.
If you use condoms perfectly every single time you have sex, they’re 98% effective at preventing pregnancy. But people aren’t perfect, so in real life condoms are about 85% effective — that means about 15 out of 100 people who use condoms as their only birth control method will get pregnant each year.

Related to another current thread talking about unlikely occurrences still occurring, I wonder why they've framed it as "15 per year"? If something is "85% effective" doesn't that mean it fails 15 out of every 100 uses? And therefore the actual yearly rate would depend on how often it was used.

What if someone only has sex (with a condom) once a year? What if they do it a thousand times?

The idea of the timeframe of a chance occurrence interests me. Is it "one-in-a-million" per day? In a lifetime? Ever?

I also wonder if they're saying "condoms are 98% effective at preventing pregnancy when you have sex around the fertile window" - which changes things dramatically. I think the chance of getting pregnant each cycle is about 30%, and within a year about 70-80%. So that's quite a few different factors to be multiplied together (plus the combatants' ages would need to be considered also).

I think if it was me I'd want it framed as "condoms when used properly don't let sperm through x% of the time". Seems a bit more accurate.

Anyways, I think the figures quoted already take all that into account: they seem to come from a John Hopkins/World Health Organisation handbook:

1620392385675.png
http://apps.who.int/iris/bitstream/handle/10665/260156/9780999203705-eng.pdf

Now just factor in how much sex people are having (average about 1-2 times per week) and how often they're doing it during the fertile window and I guess we get to a true "effectiveness rating" for condoms.

Though, in any case, I'mma agree with Deirdre on this one.

Plus: always check the moon. ;)
 

Mendel

Senior Member.
Related to another current thread talking about unlikely occurrences still occurring, I wonder why they've framed it as "15 per year"? If something is "85% effective" doesn't that mean it fails 15 out of every 100 uses? And therefore the actual yearly rate would depend on how often it was used.
The effectiveness of contraception methods is by surveying the contraception methods used and tracking pregancies; they are not surveying single uses.

This has long been established and makes all methods comparable. See https://en.wikipedia.org/wiki/Pearl_Index for more information.
 

Rory

Senior Member.
Thanks for pointing that out. It was interesting to read the shortcomings and problems with the Pearl Index. Seems like it's about time they replaced it with something a bit more accurate and representative.
 
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