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I don’t know about you, but sometimes the weather gives me whiplash. It just feels totally unpredictable! Well — maybe not to some people:

Robert SHMERLING: My grandmother — she would say that she could predict the weather, that if it was going to be colder or damper, her arthritis would be more severe. She would be able to do less activities. And it was a very clear connection for her. There was no question.

That’s Dr. Robert Shmerling. He’s the former clinical chief of the Rheumatology Division at Beth Israel Deaconess Medical Center in Boston.

SHMERLING: Rheumatology is the study of rheumatic diseases, which, broadly characterized, are inflammatory conditions — especially ones that affect the joints — as well as other joint diseases and other inflammatory conditions that affect other parts of the body.

Rob’s retired now and currently writes for Harvard Health Publishing, an arm of the medical school. We reached out to him because I’ve been thinking a lot about this popular notion that weather can affect joint pain. As a rheumatologist, Rob’s had tons of relevant experience, with a practice spanning more than 30 years. And there’s a lot to get a handle on. First of all, there are more than a hundred kinds of arthritis — a couple of which you’ve definitely heard of.

SHMERLING: Well, far and away the most common cause of joint pain that we can at least link to a disease is osteoarthritis. That’s the wearing away of the lining of the joint, which then leads to irregularities and friction, discomfort, stiffness — and limited motion. It is a non-inflammatory condition, or at least largely non-inflammatory. Whereas rheumatoid arthritis is inflammatory. And it’s auto-immune, where the immune system appears to be attacking the lining of the joints and causing the inflammation, the swelling, the redness, the warmth — features that we don’t see as much of in osteoarthritis. The pain structures within the joint are the same — so, we’re talking about bone and cartilage and tendons and ligaments — but the physiologic changes within the joint are so different that, that it does translate to differences in symptoms. So, it’s important to be specific about the one that you’re referring to.

Many of the existing studies of the relationship between weather and joint pain don’t, however, zero in on one kind of condition.

SHMERLING: Sometimes it’s osteoarthritis, sometimes it’s a rheumatoid arthritis. Sometimes it’s a blanket term called musculoskeletal pain, which can include tendonitis, bursitis, injuries of various sorts of back pain. So, it really is important, I think, to try to separate them out.

According to the C.D.C., in 2013 the total medical costs and earnings losses in the U.S. that were attributable to some kind of arthritis were $303 billion — or 1 percent of the U.S. G.D.P. If weather is contributing to those costs, it sure would be great to know.

SHMERLING: It is complicated and very hard to study, given all the variables. There’s either no connection or we haven’t cracked the case.

From the Freakonomics Radio Network, this is Freakonomics, M.D. I’m Bapu Jena. I’m an economist and I’m also a medical doctor. Each episode, I dissect an interesting question at the sweet spot between health and economics.

Today — I’m betting most of you know someone who complains about joint pain during bad weather. People have been drawing links between the two for a long time.

Adam RODMAN: It’s many hundreds of years old — it’s probably thousands of years old.

In fact, back around 400 B.C., Hippocrates, the Greek physician, noted the effect of weather on chronic ailments — just like Rob Shmerling’s grandma.

SHMERLING: I was a little kid, I think the first time I ever heard that.

So, joints and weather — a lot of people believe it’s “a thing.” But — is it true? And if it’s not, why do so many people still think it is?

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Some things are really hard to figure out, and this is one of them. Not that there haven’t been plenty of studies out there in the last several decades. But none of them is truly conclusive. Some suggest that weather affects the joints. Others don’t. But from those studies, what we do know is that weather seems to affect our perception of pain when the weather is “bad.” But what does “bad weather” mean exactly? There are a lot of overlapping elements.

SHMERLING: Right. So when a patient tells me that they feel worse in certain weather conditions, sometimes they’ll say it’s damp or cold weather. Sometimes it’s temperature. Sometimes it’s humidity. Sometimes it is changes in weather. Barometric pressure is a big one — patients won’t necessarily know that except by watching the weather report. So studies have looked at all these things and other factors as well — wind gusts, average wind speed — variables that I hadn’t even thought about as being relevant to joint pain. There’s some small studies showing some effects that are positive. There’s a 2007 study from Tufts where increased barometric pressure and lower temperature seem to correlate with osteoarthritis-of-the-knee pain. But then there’s a literature review from 2020 from the UK and they concluded that we really don’t have a handle on this.

A 2015 study from the Netherlands used data from 810 people with osteoarthritis and concluded “a causal relationship exists between joint pain and weather variables, but the associations between day-to-day weather changes and pain do not confirm causation.” So, they thought that there might be a connection seasonally, but not between a Wednesday and a Friday of the same week.

A few years ago, I got interested in this very same question and wondered whether a big data approach might tell us something useful. So my co-authors and I studied Medicare claims from over 11 million office visits. And we lined up those doctors’ visits with information from weather stations near doctors’ offices — information covering the seven days leading up to the patients’ visits.

We looked to see whether doctors were more likely to report diagnoses of joint pain on rainy days compared with non-rainy days. Or during really rainy weeks versus not-so-rainy weeks. And we made these comparisons within the same area, since places like Seattle are clearly different than places like Miami.

Rob wasn’t involved with the research, but he heard about it:

SHMERLING: Over 1.5 million patients and over 11 million outpatient visits — I mean, that’s some major data, looking at rainy days and non-rainy days and back pain, and they actually found a very slight increase in back pain on the non-rainy days! 

It’s true. We didn’t find that doctors were more likely to bill for joint pain on rainy days. But that doesn’t mean patients didn’t have more joint pain on rainy days. For example, my study only measured cases in which patients saw a doctor. And that leaves out a lot of people.

SHMERLING: If you call your doctor with back pain, you might see them in a few days, you might see them in the same day, or you might see them in two weeks when your appointment’s coming up anyway.

We thought about that and reasoned that if joint pain really was affected by the weather, people who’d scheduled a visit with their doctor weeks or months ago might still complain of joint pain on that day if it was raining outside — and that doctor might record it. But doctors didn’t seem to, which to us suggested that if patients did have more pain on rainy days, it didn’t rise to a high enough level to get a doctor’s attention.

SHMERLING: You wait, give it some time, and see if it gets better. That’s sort of, for-better-or-worse, the state-of-the-art with respect to this question.

 So, what could be going on here? Why do so many people still believe there’s a link between joint pain and bad weather — even when it’s been hard to actually show? Let’s start by looking at the most frequent complaint from Rob’s patients.

SHMERLING: In terms of the weather, the most common thing I would hear is damp and cold. I would hear that over and over from patients          .

All right: DAMP. How would higher humidity affect, say, your knee, when it has osteoarthritis, which is the most common joint ailment? How would that work?

SHMERLING: Great question. And I don’t have a ready explanation. I have read about — there’s this concept of the “microclimate” around the skin that surrounds the joint, and that if it’s more humid, and the so-called “vapor pressure” from sweat, sweat glands and outside humidity goes up, then that vapor pressure — again, whatever that is — somehow gets transmitted to the joint and causes more pain. But I don’t find that very satisfying. It sounds like, as we call it, a “hand wave.” It’s really just a theory.

And what physiological mechanisms could also possibly be at work?

SHMERLING: It really comes down to pretty much just pure speculation. It’s very hard to come up with anything that’s compelling or reasonable. I think the things that have been posited most commonly are: perhaps there are nerve endings or nerve fibers within ligaments or tendons or the joint itself, that, because they are sensitive to mechanical pressure, they can — in some people at least — be so sensitive that they can sense atmospheric pressure, or atmospheric changes. No evidence for that to support or refute it really, but that’s one theory. 

Another theory is that it’s a lubrication problem within the joint. We all have a small amount of something called “synovial fluid” in our joints. And the idea is that maybe this fluid is somehow altered by cold or humidity or barometric pressure — or fluctuations of any of those.

SHMERLING: No evidence for that, but that’s another theory. I think maybe the most common one I have heard is that it’s kind of a mind-body psychological connection — that we know the weather can have an effect on our psychological outlook, and we also know that our psychological state can alter our perception of pain. All of that is sort of well-accepted dogma. So, if that’s true, then why shouldn’t the weather be able to change our perception of pain, whether it’s osteoarthritis or tendonitis or something else?

Don’t forget: Your brain is a physical part of your body too!

SHMERLING: So, this is why — you know when people say, “Is it all in your head?” Well, all pain is in your head, because that’s how we perceive pain. So, I think if you’re a person living with chronic pain — when it’s going to get better and worse, and why it’s there in the first place — I’m imagining my patient watching the weather forecast and it says, “In three days, it’s going to be rainy and cold.” I think having this expectation that you might feel worse in three days — and then if it happens, it’s understandable. I think that ‘s very reassuring to a lot of people. And then also they know on day four, day five, when the weather clears up, they can have an expectation of improving.

There are some other explanations too, ones that aren’t physiological. Way back in 1996, the physician Donald Redelmeier, who’s been a guest on this show, and the psychologist Amos Tversky found no association between joint pain and weather in the people that they studied. But they did find that people do something called “selective matching” which can lead people to perceive patterns where none actually exist. That’s one psychological explanation — but there are others.

Carey MOREWEDGE: If I have a belief that there is a correlation or a connection between the weather and joint pain, then I’m going to have some kind of stake in that hypothesis.

That’s Carey Morewedge. He’s a social psychologist and Professor of Marketing at the Questrom School of Business at Boston University.

MOREWEDGE: My research broadly studies the causes, consequences, and how to mitigate cognitive biases.

What’s a cognitive bias? Basically, it’s a tendency to process certain information in a consistently wrong way.

MOREWEDGE: A cognitive bias is this kind of systematic error that results from either some kind of way that we perceive the world or some kind of way that we process information.

Is there a cognitive bias that might explain why people perceive a relationship between joint pain and bad weather?

MOREWEDGE: Well, the one that leaps to mind is confirmation bias — if we’re just looking for things that confirm our beliefs and disconfirm their alternatives. So, if it’s raining and I feel joint pain, there I see a relationship between joint pain and the weather, but I’m not necessarily attending to joint pain when it’s sunny and dry. Or I’m not paying attention to the absence of joint pain when it’s raining.

And in what context are we most likely to find confirmation bias driving us? Well, they don’t call it the “echo chamber” for nothing.

MOREWEDGE: The internet is another way that people are biased in their testing of these kinds of hypotheses, because there’s so much information out there now. And in general, people find stories and anecdotes to be much more compelling than they do data. And so when they’re searching and sifting through this evidence to try to explain their joint pain, stories that are going to resonate with the hypothesis that they start with will ring more true or seem more credible to them as well.

But what if the connection is not actually true? Could there still be a benefit to believing that the weather makes your joints hurt?

MOREWEDGE: That’s a really fascinating question. And there is some work in this area. And what that work suggests is that a lot of the kinds of emotional responses that we have, both positive and negative, are heightened by uncertainty.

Like the uncertainty of a chronic pain condition that just comes and goes.

MOREWEDGE: In those kinds of cases, that uncertainty can prolong those kinds of negative states, and people will feel some kind of comfort for having an explanation or having some kind of reason or ending that uncertainty.

In other words, assigning blame to the weather for joint pain can give some people a sense of control over what is really an uncontrollable, often unpredictable symptom. Coming up: the relationship between weather and joint pain is just the tip of the iceberg when it comes to widely held — but hard-to-prove — beliefs in medicine.

RODMAN: It’s based on this much older cultural understanding of medicine that has died out in the west for 130, 140 years.

I’m Bapu Jena, and this is Freakonomics, M.D.

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Now, before the break we explored the widely held belief that weather affects joint pain. But there are so many other beliefs in medicine that are just like that — could be true, but not a lot of good evidence one way or the other. And I wondered how these sorts of beliefs come to be.

JENA: So, Adam, thank you for talking to me today. I realized that we’re in the same town, but I don’t think we’ve ever met in person before.

RODMAN: No, we haven’t. It — we literally probably work, what, like a 10th of a mile from each other?

Adam Rodman is just the guy we need.

RODMAN: My name is Adam Rodman. I am a general internist — so I am a practicing clinician, I work in both the inpatient and the outpatient setting at Beth Israel Deaconess. And I’m a huge nerd. I’m a historian of diagnosis and medical epistemology. And I run a podcast, with the American College of Physicians. 

JENA: Can you tell me a little bit about it?

RODMAN: Yeah, it’s, it’s called Bedside Rounds. And the whole idea is it’s a historical exploration of how modern medicine came to be. Like, what does it mean to be evidence-based? And this is like a particular obsession with me because when you start to really dig down into different epistemologies, we know things as physicians in different ways.

JENA: So, can you just — can you just define: when you say epistemology, what do you mean?

RODMAN: Yeah, so epistemology is how we know things. So a classic epistemology might be experimentation, right? You know things by running experiments, by running randomized controlled trials. Or you look by compiling a bunch of data together and looking for patterns. It might be personal experience. So that’s what I mean by different epistemologies. It just means different ways of knowing.

JENA: So you’ve probably heard this relationship between joint pain and rain and cold weather that people describe. Have you thought about this issue? What’s your sense of it?

RODMAN: Oh, so that’s a — this is a fascinating one because this association, right — it’s many hundreds of years old. It’s probably thousands of years old. It’s based on this understanding of medicine that has died out in the West for 130, 140 years — let’s call it a traditional Western nosology. The whole idea is that all health is based on the balances of the four fundamental body humors, which are yellow bile, black bile, phlegm and blood.

Ok, let’s slow down a sec and I’ll explain what Adam just said because it feels like something out of Game of Thrones. These four so-called “humors” of the body are yellow bile, black bile, phlegm and blood. A long time ago human health was thought to depend on the balance of these humors to prevent disease.

RODMAN: This is the dominant medical idea really, let’s say, to the 18th century in elite circles. And what’s crazy is, it lasts until the early 20th century and in some lay areas in the United States.

This “humor-ISM” — as strange as it may sound to us today — was at least a naturalistic theory, based on physical concepts.

RODMAN: These are not supernatural body fluids, even though I’m not a hundred percent sure what yellow bile or black bile are. But, like, what imbalances them? One of the big answers is the environment, right? So it’s a really, really old idea that our joint pain might act up because of shifts in the humors that’s caused by shifts in weather. And that’s why I think it’s such a fascinating idea, because we’ve somehow seen this folk belief that has been transferred probably millennia that people still believe today, though obviously, the epistemological framing — like no one believes in the humors anymore, but we still have the belief.

JENA: So I would kind of describe what you’re saying and break it into two ways. So there’s a perceived relationship between the way our body feels, let’s say it’s joint pain and bad weather. And it could either be a true relationship — like there’s literally something about the weather that influences a joint — or it could be a perceived relationship. And it makes me wonder, like, are there situations where there are old wives’ tales that are actually true, that are causal? You know, people will say that you’re more likely to get sick when it’s cold outside. Obviously there’s a lot of reasons why that might be true. If you were to just rattle off a couple of explanations of why that might be the case, what comes to mind?

RODMAN: This is your classic old wives tale, right? “Put on your coat or you’ll get a cold.” And I think most of us who, you know, use the framing of germ theory are like, “That’s ridiculous — it is caused by a virus.” But let’s say — from a merchant in like 18th century London, right? They would have had no idea of — obviously they had no idea of germ theory, or God forbid, viruses. They probably had never heard of contagion, but they would still see this observation and they would fit it into their explanatory model — that disease is caused by changes in the weather, so it imbalances our humors. That’s got to be what’s going on. And you can see how some of these ideas are formed and persist into the modern day.

JENA: Now I’m just thinking about like all the things that I’ve heard in the last couple of weeks, and by the way, most of the things I hear from my mom Vitamin C and colds. So, you know, when you go to the CVS or Walgreens or whatever, there’s like this whole aisle of things designed to improve cold symptoms.

RODMAN: Oh, that’s — yeah, yeah, yeah.

JENA: Do they work?

RODMAN: Um, well, I mean — no. The only thing I know: zinc does seem to shorten cold symptoms. To me, the more interesting question is why are people convinced that Vitamin C does work?

JENA: Yeah. Why are they?

RODMAN: Well, I think there’s a couple reasons. Vitamin C actually is vasodilatory — like you can feel taking high doses of vitamin C. You’ll flush a little bit. So people feel a physiologic effect so they assume it works more. So I think vitamin C has that I don’t want to call it sexy, that’s not the right word, but it has this, like, “cool factor” to it.

JENA: Yeah, that’s what the C stands for — Vitamin C.

RODMAN: Well, and it’s funny because it’s super — like if you have scurvy, I mean, literally vitamin C is “ascorbic acid”. It’s anti-scurvy acid. It’s great treatment for that. Colds are the perfect therapy for any sort of treatment because they get better on their own.

JENA: Yeah, I think is actually really important. So, you know, how do we think about a disease that is going to get better on its own much of the time? It lends itself to the situation where we would ascribe the improvement to something else. It could be anything, literally. I mean, methodologically, this is why you need a control group, because you actually can’t tell whether or not the improvement that you observe is because of that intervention or something else.

RODMAN: We like to attribute the things that we do as having an effect. And this happens all the time, both in my inpatient and outpatient practice, often with herbal medicines or traditional medicines, which you worry, for example, in a patient who has cancer, if they are seeking out alternative like herbal treatments, instead of seeking like appropriate cancer care. And I mean, I understand, right? If anything, being a historian gives you good insight into why people believe the things that they do. So my own personal approach is to try to be very understanding of what psychological role, those therapies might be playing. I’ve definitely seen harm from these beliefs. And it’s challenging, right? Because people — you know, there’s mistrust of the medical system. And, to be clear, doctors are also guilty of having a lot of beliefs that are not necessarily based in reality. Right? I remember when I was a medical student, some of my fellow medical students, and I’m probably guilty of this as well, would scoff when a patient comes in and says, “You know what? My normal temperature, I run low, so 99.9 is a fever for me.” a lot of healthcare professionals now would roll their eyes at this. But what’s really interesting is if you look at where 98.6 as the regular temperature comes from, it’s from the 1860s — this is the birth of clinical thermometry. But there’s no evidence of the average human body temperature, you know, until the 1980s in vaccine trials, when there’s, like, really well-done studies that pretty much definitively proves that the average human body temperature is probably 97.8. So, like, what your patient was telling you turns out to be completely right. And we dismissed it. And if you actually look at the strength of the evidence that doctors were operating on, well, it’s no different than the patient who insisted vitamin C makes their cold better, right? We’re passing down information and we aren’t really looking at our own beliefs.

JENA: You can imagine seeing a patient, either in the hospital or in your clinic, who has a temperature reading of 99.8 — and that would not prompt someone in the hospital to obtain blood cultures or to get a chest x-ray to evaluate for a cause of that fever.

RODMAN: And it does matter for outcomes! There’s a great analysis  done of outpatients — hundreds of thousands of data points at MGH — that looked at, fever and predictive things for fever. And variation from the person’s baseline is what matters and has real outcomes.

In other words, if your baseline temperature is 97 degrees, then a raised temperature of 100 degrees will have a bigger effect on your health than on someone whose baseline temperature is higher, maybe around 98.6.

JENA: All right. Going back to this question about the joint pain and rainy days and cold weather, can you kind of articulate why there could be a causal link

RODMAN: Well, I can imagine, right? If you look at the bursa in our joints, they are fluid-filled sacks. So you could imagine a situation where the atmospheric pressure changes that are associated with weather changes, causes swelling changes in those fluid filled sacs. There is — I think there is a reasonable epistemological model by like a physiologic standpoint of, of how that would happen. So I don’t think it’s crazy to think that. Would that be your hypothesis as well?

JENA: So I think there’s probably two things that could happen. One is sort of something mechanical with the actual joint. And two is how the mind perceives any given level of symptoms. I mean, you know, on a rainy day you’re going to perceive the world differently than you are on a sunny day.

RODMAN: Yeah, your aches and pains might be more noticeable too. Yeah, that’s great — I didn’t even think of that.

SHMERLING: Acute pain that lingers gets you thinking all kinds of catastrophic things are going on.

Again, rheumatologist Rob Shmerling — 

SHMERLING: This happened with me just last week. I had bad back pain. And I was pretty sure it was from moving very heavy plants. But after it didn’t get better in a few days, I started to imagine all kinds of terrible scenarios — you know, a little information can be a bad thing. I went to a bad place — and then the next day I was better. So you’d think I’d learned from previous experience. But everybody does this. 

He knows how to talk to his patients about their outlook.

SHMERLING: I don’t brush it off and say, “Well, there’s no good science on this, therefore it’s not happening.” If someone says they have pain, I believe they’re having pain. I hear it too often to discount. And what I say usually is that we just haven’t figured this out yet.

Medicine is complicated. It’s easy to forget how much we don’t know when we’re surrounded by how much we do know. That knowledge, which is so different today than it was 50 years ago, has obviously made a lot of things possible. But it’s also probably made us more skeptical of things that we don’t understand, things that we can’t measure with a blood test, or see with an image from a CT scan or MRI. I actually don’t know whether our joints are affected by the weather. Or if it’s just something that many people perceive. To me, the best available data don’t suggest a clear link. And there are good explanations for why people may perceive the patterns that they do, not just with weather and joint pain but with lots of medical folklore. But it’s always worth being cautious, which is why I want to end with Rob Schmerling:

SHMERLING: I think a good dose of humility is in order when you don’t really understand something as well as you would like. I’ve always been skeptical and a person who says, “Show me the evidence,” but once you realize we don’t have the perfect evidence to make a determination, I think we’re all served best to keep an open mind.

There you have it — that’s it for today’s show. Thanks to Rob Shmerling, Adam Rodman, and Carey Morewedge. By the way, if you want to try to de-bias yourself, check out a video on our show page at Freakonomics-dot-com. It’s based on some of Carey’s research. Also, if you enjoyed this episode, you may like an earlier one, called “Is the Placebo Effect for Real?”

Coming up next week: doctors-in-training don’t work as many hours as they used to.

ROTHSCHILD: We showed that the shorter duration shifts resulted in reduction in medical errors. So that was the good side of that study. But there were some unintended consequences.

Working fewer hours means an increase in something else: handoffs.

ROTHSCHILD: Poorly done handoffs resulted in more errors and adverse events.

We’ll talk about what it means for patients when a doctor’s shift ends in the hospital —and also, the challenges of another kind of transition.

SABETY: The key nugget here is that many patients, myself included, value having a relationship with their physician.

That’s all coming up on the next episode of Freakonomics, M.D. Thanks to all of you, for listening, writing in, and supporting the show. If you haven’t told your friends and family about the show, you should. And if you can, leave a review for Freakonomics, M.D. wherever you get your podcasts. It really helps us out.

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 Freakonomics, M.D. is part of the Freakonomics Radio Network, which also includes Freakonomics Radio, No Stupid Questions, People I (Mostly) Admire and Off Leash. All our shows are produced by Stitcher and Renbud Radio. You can find us on Twitter and Instagram at @drbapupod. This episode was produced by Sarah Lilley and mixed by Eleanor Osborne. Our senior producer is Julie Kanfer. We had help this week from Emma Tyrrell. Our staff also includes Neal Carruth, Gabriel Roth, Greg Rippin, Rebecca Lee Douglas, Morgan Levey, Zack Lapinski, Ryan Kelley, Jasmin Klinger, Lyric Bowditch, Jacob Clemente, Alina Kulman, and Stephen Dubner. Original music composed by Luis Guerra. To find a transcript, links to research, and a newsletter sign-up, go to Freakonomics.com. If you like this show, or any other show in the Freakonomics Radio Network, please recommend it to your family and friends. That’s the best way to support the podcasts you love. As always, thanks for listening.

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JENA: The, um…. um … what was I going to say? I forgot what I was going to say. I forgot what was going to say.

RODMAN: I have that effect on people, I’m sorry.

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Sources

  • Carey Morewedge, professor of marketing at the Questrom School of Business at Boston University.
  • Adam Rodman, internal medicine physician at Beth Israel Deaconess Medical Center and host of the Bedside Rounds podcast.
  • Robert Shmerling, senior faculty editor at Harvard Health Publishing and former clinical chief of the Rheumatology Division at Beth Israel Deaconess Medical Center.

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