A study of nearly six million Swedish women has failed to detect significant association of SARS-CoV-2 vaccination with menstrual irregularity.
This caught my eye, mostly because of the sample size, although I’ve only scanned the text. Seems to be another solid piece of information to fight COVID-related ignorance.
Link to PDF spoilered below:
I would hardly call this “COVID-related ignorance”; there are other studies that have shown the opposite, as well as survey evidence. It may not be a big deal in the grand scheme of things, but there’s a fair amount of evidence that it’s a real side effect that occurs sometimes, and even if it turns out that it’s unrelated, it’s not crazy or ignorant to think that it could be a vaccine side effect. This isn’t “vaccines make you magnetic” territory.
As I understand it, the research I’ve reported is newer than yours and involves a sample size that’s 300 times larger (six million vs. 20,000).
Oh sure, it might be a better and more definitive study, and it may turn out, as the body of research grows, that there is no association at all. I’m not disputing any of that. What I do object to is writing off the idea that there could be a link between menstrual irregularities and vaccination as inherently ignorant, especially when there appears to be some legitimate evidence on both sides. I don’t quite know how to articulate why this bothers me so much, but it feels to me like vaccination and other aspects of the COVID response have become so politically-coded that people are unwilling to acknowledge that side effects and other downsides can be real, and are not just right-wing crazies making stuff up; and in this particular case, it intersects with a long history of medical professionals dismissing what women report about their own bodies.
The only proven scientific relationship between vaccines and humans is that vaccines have saved a huge number of lives. This is a historical fact. Can certain individuals be adversely affected by a vaccine? Of course! You name it, and someone is allergic to it. Despite the desperate attempt of anti vaxxers to discredit vaccines, the results of this study is yet another of their many failures.
It’s sort of an odd study. I suspect it was retrospective. They didn’t ask women in real time about their menstrual regularity, they looked at their medical records to see if they had sought medical care for menstrual irregularity.
So the prior results that being vaccinated might disrupt the menstrual cycle briefly are not disproven. Rather, they’ve found that there’s no evidence of problems serious enough to see a doctor about.
It’s really a shame that menstruation wasn’t one of the symptoms followed in the initial studies, along with local pain and stomach aches. That would have given definitive information up front. And it would probably have shown that transient menstrual irregularities were common (because anything that disrupts the body tends to do that, so anything that can cause fever, etc. is likely to temporarily disrupt the menses) and like this study, it would also have shown those issues weren’t serious, and cleared up on their own within a few days.
If I may offer a quick aside in lieu of starting a new thread in FQ:
Are such disruptions in the menses well-understood from a physiological standpoint (esp. causes and effects)? If so, what seems to be the biological mechanism at play when, say, a fever affects menstruation? Maybe hormone production is temporarily affected?
I dunno. I know that my menses were always influenced by my stress level – for instance, I never got my period when studying for finals, and then did immediately after the exams (once, during the exam). I also never got my period during the summer vacation when I used an outhouse, for the entire time I menstruated (and my sister did every single year.) Or for instance, when I took the summer after college to bum around Europe, I didn’t get my period all summer. I asked my gynecologist about that when I returned home, and he said it was common for stress (both physical and mental) to disrupt the menstrual cycle, and there was nothing to be concerned about.
And I read several medical commentaries during the pandemic that it should have been expected and documented by vaccine testing, and it hadn’t been in the routine list of “stuff followed” because there aren’t a lot of new vaccines studied in women of childbearing age – most new vaccines are targeted at kids or the elderly. (And, men are blind to women’s issues, of course.)
So I don’t know whether it’s well-understood from a physiological standpoint, but it is common and well known and well documented as a thing that happens.
Something that right-wing crazies did do to discredit the vaccine was to latch on to any public reporting of vaccine side effects, however grounded, and then shout from the top of the social-media mountain: “THIS IS WHY THE VACCINES MUST BE SUMMARILY HALTED!!!”
Reports of post-vaccination menstrual irregularities were swept up in this, regrettably. Puzzlegal’s point that menstrual changes should have been tracked and considered during vaccine testing is well-taken.
I just want to be really explicit and say that this new study doesn’t contradict the studies you cite. They say that a lot of women reported that their period immediately following covid vaccination was heavier than usual, and the new study says that there was no increase in women seeing a doctor about menstrual irregularities after covid vaccination.
No women in her right mind sees a doctor after a single heavy period. Especially during a pandemic when it is unsafe to go to a medical facility. What you do if you have an unusually heavy period is bitch to your friends about it.
Yeah in my experience it was a temporary issue after vaccination. An early period, which happens from time to time in the 40 years one has periods. I am pretty sure I mentioned it here on the SDMB, or maybe somewhere else, and several other women chimed in and said they experienced “period weirdness” too and that was that. For most women, “period weirdness” is the norm and it would be a weird year if you just got it every 28 days with the same flow.
This study shows that there was no prolonged or permanent weirdness.
Considering that the first COVID vaccines coincided with continuing shutdown, we were STILL under a lot of stress.
I would take ANY single “definitive” study about COVID with a big grain of salt, even if it does get published by the BMJ.
In this case, antivaxers leaped on early reports to declare that not only were the effects incontrovertible, but that Covid vaccination caused infertility.
Physicians/researchers have repeatedly looked into reports of purported vaccine side effects without dismissing them as coming from “right wing crazies”, and ultimately science tends to win out. The large Swedish study of menstrual changes adds to the earlier body of evidence, which suggested that any alterations were minor and temporary.
Speaking of published research looking into antivax claims, there’s a new large-scale study that refutes allegations of the “Died Suddenly” crowd.
Others have addressed other issues, but I’ll just comment on this: Once a sample size gets big enough, it doesn’t much matter how big it is: A study of six million people isn’t going to give significantly better results than a study of 20,000. If there are significant differences between the two studies, it’s due to something other than sample size (different methodology, addressing a slightly different question, etc.).
Does that make sense as a general rule? Wouldn’t it depend on the specifics of the study?
Yes, it does make sense as a general rule.
My father used to say that if you have to squint to see statistical significance, there is no biological significance. That is to say, it’s true that there might be something that can be shown to be statistically significant with a sample of 6M that’s wasn’t statistically significant in a sample of 20K. But it’s not a very interesting or important thing. Because it doesn’t really matter to you if your odds of catching X are 1 in a million or 2 in a million.
And Chronus is right in general. If the studies have different outcomes, (not just that one finds statistical significance and the other doesn’t) it’s not because of sample size, it’s because they asked a different question, or looked at a different population, etc.
Which is exactly the case here. The larger study doesn’t contradict earlier studies that reported menstrual irregularities after vaccination. What it found was that there was not an increase in visits to doctors for menstrual issues. That’s totally compatible with women noticing that they had a heavy or a late period immediately after vaccination. It just means that there weren’t any issues serious enough to see a doctor about. Just like people noticed arm pain immediately after vaccination but didn’t flock to their doctors about it.
One place where those types of sample sizes make a big difference is in genetic studies, exactly because each thing being measured is not “interesting or important” on its own. Any particular changed allele might contribute to the variance in a trait by a very tiny amount. It is biologically real, but of such a low importance that it isn’t detectable with 20,000 subjects, but is detectable with 6 million. Add up all of these tiny changes, and it can make a big difference in the trait of interest.
Additionally, in the genetics example, there are massive multiple testing issues to be accounted for. The study isn’t looking at one change, but millions of possible changes across the genome. In order to get a real p of 0.05, you might need to have an observed p of 0.00000005. That needs a big n.
Fundamentally, it comes down to effect size. Are you looking for something that accounts for 80% of the variance in a trait, 15%, 1%, 0.01%? That will change your sample size, and a study with 20,000 subjects might be underpowered. It is a reasonable criticism that finding something that accounts for 0.01% of the variance is pointless, even if the observed effect is real.
If you are interested in the topic of periods and the COVID vaccine, This Podcast Will Kill You interviewed Dr. Kate Clancy about periods, and they talk about this. She is senior author on the survey paper linked by @Fretful_Porpentine. One of her points is that so little research is done on periods that it can be hard to say if their observed disruption of periods is even unusual. There can be a real disruption, but it might not be clinically relevant.
https://thispodcastwillkillyou.com/2023/04/25/special-episode-dr-kate-clancy-period/