TRANSCRIPT
Okay, welcome again to the Better Brain Fitness podcast. I am Dr. Josh Turknett, and as usual, I am joined by my Steamy co host, Dr. Tommy Wood. What’s up, Tommy? Ah, hello. Both literally and figuratively today. So today’s we’ve got a great question. It was an audio submission from Dimitri.
And his question is “can sauna help reduce the risk of Alzheimer’s?”
Alright, so, excellent question. And Tommy is fielding this one today. He’s going to tell us about the evidence, or lack thereof, for sauna, and it’s effects on dementia and Alzheimer’s disease. This is a, a super interesting question, thanks Dimitri, and, and I think there’s a number of ways that we can, we can tackle this.
It’s worth saying up front, there are a number of potential reasons why sauna may be beneficial, and maybe we can go through some of those first. So, assuming this is a dry heat sauna, like a traditional Scandinavian sauna, so you’re gonna get in, and the temperature’s gonna be somewhere around, You know, 80 to 100 degrees Celsius, and there’s gonna be a small amount of humidity.
Maybe you have some some water to the rocks. I like to do that. So you get like a little bit of steam, but it’s not like a steam bath. And in a steam bath, you can’t sweat as much because it’s so humid, so there’s probably some benefit from the sweating itself. So this is the kind of sauna that we’re talking about, and that’s probably what’s best researched because it has historical and cultural context, particularly in Scandinavia.
So in terms of… When we get hot, like we do in a sauna, there’s a number of benefits that seem to mirror a lot of the benefits of exercise. So your heart rate increases you see a number of benefits, both short term and longer term, on things like blood pressure, that Dimitri mentioned, but also endothelial function, so how well, you know, the function of our blood vessels.
And a lot of these kind of mirror some of the benefits of aerobic exercise, and it’s probably having similar effects, because you’re increasing heart rate. You’re you’re also vasodilating, so you’re kind of pumping against a low pressure system. This seems to be beneficial for the heart and our vascular function.
There’s also some interesting, , sort of biochemical mechanisms that that might be interesting. So, things like upregulation of heat shock proteins, which are important for regulating for a lot of protein production and making sure that we’re clearing. , proteins that have aggregated that are no longer useful.
There’s this thing called proteostasis that happens as we get older and our cells become dysfunctional over time. Heat shock proteins may help with things like that. There’s some evidence that after short term heat exposure, you can get upregulation of some other things involved in mitochondrial biogenesis, as well as decreases in inflammation.
So lots of things, and again, these, these are the same kinds of responses that you’d see in response to aerobic exercise, so similar benefits there. There’s some data that suggests that sauna after exercise can also augment some of those, , same processes increasing things like, , growth hormone as well as improving some of those sort of cardiovascular responses.
There’s, there have been studies. Where, , short term people have been exposed to sauna and it’s had some antidepressant like effects. And this may be through, you know, all those, those mechanisms and, and others. And we know that depression is, is a risk factor for future dementia. So it’s possible that it may be having some, some mental health benefits.
Some people suggest this could be through mechanisms like, , the production of brain derived neurotrophic factor. This is something that’s also produced during exercise, and it sort of supports brain function. We think that if you make it in your body when you exercise, or when you’re exposed to someone, that it can get, get into the brain and have some benefits in terms of supporting neuronal health, , and function.
And there are also, there have been some, some interesting studies on… How heat exposure can help maintain muscle mass, particularly in like a bed rest study, you have people who don’t move at all for a period of time, if you then heat the muscles, they lose less of their muscle mass. So if, is it, you know, a regular sauna, is it helping?
To prevent the kind of loss of muscle mass that hypothetical hasn’t been studied, but certainly possible. The, the final interesting Potential reason why a sauna could be beneficial is, is through the act of sweating. Sweating is one of our inbuilt detoxification mechanisms. And there are actually Lots of heavy metals in particular, as well as some, you know, plasticizers, bisphenols, things like that, that can be excreted in sweat.
And If you’re sort of thinking about dementia risk at a population level, we know that heavy metals probably have a role to play in some people’s risk factors as do some of these other environmental type toxins. So if you expose everybody to sauna, they all sweat a bunch more. This is probably, you know, could plausibly help decrease some risk at a population level.
And if you’re exposed to a lot of these things, I do think sweating is a good thing to do. Be it through exercise or sauna, because it’s, it’s just one of the mechanisms that we normally would use or activate as part of normal detoxification, just like your liver and your kidneys do every day. Sweating is part of that and I think that’s a good reason to sweat regularly.
So that’s kind of the the potential reasons why sauna might be beneficial for, for dementia risk. , and then we can dig into, oh, and one thing I didn’t mention was also blood sugar control. , there have been some studies where people are exposed to heat. This could be in a hot tub, so it’s not sweating related, or it can be in sauna, and it seems to upregulate some of the Transporters for glucose and improved blood sugar control that’s been done in type 2 diabetics in particular.
So, we’ve talked several times about how blood sugar control is important for the brain, and, and regular heat is another reason why that could be the case. And again, that sort of mimics what happens during exercise. So lots of overlap between the mechanisms of exercise and sauna, we think, in terms of health.
There’s been a few studies two main ones and then some sort of sub analyses from the same cohort that have generated the biggest headlines in terms of sauna and both overall mortality as well as heart disease mortality risk, and then one specifically on dementia. These come from the Koipio ischemic heart disease study in Finland, which specifically looked at About two and a half thousand men, men only, in Finland in the late 80s.
And what they did was they asked them about various things, you know, questionnaires about socioeconomic status, they looked at their health factors, they measured their cardio spiritually fitness, you know, they did like an exercise test, and then they asked them about their sauna usage. And they categorize them into three groups.
One is, do you like sauna once a week, another is two to three times a week, and then the, the, the highest group is four to seven times a week. Now you’ll notice that there’s no zero times per week, and that’s obviously because sauna is, is, is a big part of culture, of, of Finnish culture. So already this is maybe different from some of the populations or.
That we, we might be exposed to in the, this is not something that is normally done. And it, that’s kind of where some of my concerns come from. So, what they then showed is that there’s this, Quote unquote dose response. So as you went from one time a week to two times per week, you saw a decrease in all cause and cardiac mortality as well as dementia risk.
And then as you went, and then you went to four to seven times per week, you saw an even bigger increase.
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Alright, now back to the show. These papers have said that that there’s something like a 60 70 percent chance of It’s a 63 percent reduction in the hazard of sudden cardiac death, something similar for all causes mortality, and a 66 percent reduction in risk of Alzheimer’s, dementia. This is a massive decrease.
Like two thirds decrease. just by adding sauna three to six times per week compared to you know, on top of the one time per week, which is the reference group. I think that there is a signal of benefit and I believe that it’s true, but the size of the reduction, I think is relatively implausible. anD there are a few things that kind of support this idea.
So, if we were to look at the original paper looking at sudden cardiac death, and the reason why I’m looking at this is because they have certain types of analyses that they don’t have in the dementia paper. The dementia paper is, is fairly sparse, and they don’t have a bunch of, sort of, the additional analyses that I would like to see, but they do have that in the cardiac death paper, and the, it’s essentially the same group of people.
So they give you curves looking at sudden cardiac death stratified by the amount of sauna these individuals do, and the curves start to separate almost immediately which basically means that within a year or two, those who are sauna ing less, are already dying faster than those who, who sauna frequently.
What this tells you is that these are just fundamentally different people, right? Sauna is not immediately reducing cardiac death. So, when you, when you then look at some of their They compare these subgroups, you can, you can see that they don’t do that in the dementia paper very well, but they do do it in the cardiac death paper, and those who are sauna-ing four to seven times a week are younger, fitter, like everything else about them is better, they have better blood pressure, um, they do adjust for socioeconomic status, but they never tell us about the socioeconomic status level across the groups, but my guess is that those who sauna more frequently are also Thank you.
But better off they have better jobs, which gives them more free time to go to the sauna. You know, maybe business is being conducted in the sauna. Basically, everything about those who saw no more frequently is better from a health standpoint. And so I think that some of Some of the signal is what we call residual confounding, which basically says that there is something else that is explaining these differences that hasn’t been accounted for statistically.
And that’s, that’s my guess as to what was happening. One way to count against that or to sort of improve some of that signal is they did an analysis in the cardiac death paper where they ignored the first five years. So you had to survive for at least five years before before they started to count.
This is like a sensitivity analysis just to kind of check how good the signal is because some of those people in the lower frequency sauna groups were just dying so much earlier and they saw. They did still see benefit, but it was that the magnitude of the effect was reduced which is kind of what I’d expect.
So, I think when you sort of look across all of this, there is certainly a number, there are certainly a number of reasons why sauna can be beneficial. There are studies in humans, randomized controlled trials where they do heat exposure and they see all these beneficial things. Like we talked about earlier, blood sugar control, blood pressure, you know.
the sort of the exercise type responses. But I think the The magnitude of the effect on dementia, saying that it decreases your hazard of dementia by two thirds, I, I don’t think that’s believable. There’s, there’s no reason why that would be the case, and I think that part of that signal is because these groups are just fundamentally different.
Those people who go to a sauna four to seven times a week, They’re younger, they have more money, they’re fitter, and that has not been fully accounted for statistically. There is one other example of why that might be the case. They did a smaller subset study of this same group where they looked at levels of inflammation by those who by the amount of time they spent in the sauna and They saw something very similar.
So the more time you spent in the sauna, the lower your levels of inflammation. They measured by a CRP. They used this to argue that sauna was decreasing CRP, decreasing inflammation, which is possible, but the opposite is also potentially true. That these people who are sauna ing more frequently, we already know they’re healthier for a number of other reasons.
They’re younger, you know, they exercise more, they have more cardio respiratory fitness. So it could be that. Inflammation is, is something that is not being accounted for, because they didn’t adjust for that in these other studies. So it’s just another thing that suggests that there’s something more going on here.
So I, I believe there’s a, there’s a potential benefit, but the magnitude of benefit that we’ve been told from these studies, I think is, is not believable, and they haven’t fully accounted for the differences in, in the, in the separate groups. So that’s where I’ve ended up. I’m a big fan of sauna.
But it’s not magic.
Are the rates of Alzheimer’s in general in Finland lower? No. Actually, Finland has one of the highest rates of Alzheimer’s disease in Europe, I believe. I did look at this once. Okay. So, great discussion. I have some questions. So, , I think one, one reason probably you like Panthana, I like sauna is in the language of the last episode that we introduced, it’s a game level intervention, right?
It’s a, it’s a heat is a stimulus to which we have been, it’s been part of our environment for as long as we’ve been here on planet earth. And I think the, the benefits that we think of with respect to heat are hormetic in nature in that they stimulate a range of adaptations that then increase our resilience, like you said, analogous in many ways to exercise here.
But our first question is, so if we remember the quadrant model that we talked about last, last episode, quadrant one, or these game level interventions. Which heat could be considered that are a game level intervention that reduce mismatch and then quadrant two or, or game level interventions that that we are using strategically in some way that may be disruptive, but that we have, , research their benefits and are using them to steer our health in a particular direction.
So do you think of sauna as. Yes. In some cases, a quadrant one type of intervention where we are reducing mismatch. And the reason being that, you know, in today’s world, we tend to spend much of our time in climate controlled environments, not exposing ourselves to temperature extremes. Could that be a factor in driving, you know, various mismatch diseases?
And do you think, do you, so do you think of that as part of kind of a mismatch reduction protocol? Yeah, that, yeah, so the question is it quadrant one or quadrant two? Yeah. There may be, there’s definitely quadrant two, but is there a quadrant, is there an argument for a quadrant one? Yeah, that’s, that’s a great question.
If we think about, like, true mismatch, like, what are, what are inputs that are expected almost physiologically? Yeah. I would probably argue, if you’re from, if you’re of a Northern European heritage, Scandinavian heritage, as I am, exposure to prolonged periods of cold is probably more of an expected input, but actually those are the same cultures that found ways to also be exposed to cold.
So it’s more extremes of heat, and interestingly, there’s some overlap in terms of the biochemical responses to temperature extremes. So heat shock proteins I mentioned, sometimes when you’re exposed to extreme cold, you also get upregulation of those same heat shock proteins. So it’s not really heat, it’s more like a temperature shock protein.
On the other side of that. Imagine you live closer to the equator, you’re probably less likely to be exposed to extremes of heat in that same way. So maybe there’s some, ancestrally related. Mismatch, based on what you, what you expect physiologically due to the environment that, that your most recent ancestors inhabited.
And so my answer is maybe. It’s not an easy question. ALICE Yeah, and, and when I think about it, there’s been Icelanders. Where they looked at, I don’t think they’ve done this with epigenetics, but they looked at single nucleotide polymorphisms, so just like regular genetics, and compared Icelanders to Norwegians.
And so the Vikings traveled from Norway and settled in Iceland. And they found these shifts in Icelandic genetics that they hypothesized were driven by how harsh the environment was. So there’s a whole bunch more of, like, genetic resilience that kind of shifted over time because you’re essentially on this barren rock in the North Atlantic that’s just covered in lava fields and glaciers, that’s it.
And that seemed to shift the genetics of the population. So that kind of says that there’s this signature genetic signature of exposure to these harsh and largely temperature driven environments that may be to help support that particular genetic milieu and its health. You know, there’s a, there’s a, there’s a case to be made for, for temperature extremes you know, and then mismatch being derived from, from not being exposed to those.
So it’s certainly possible. And the, the final thing I will say is that there’s some interesting data on how particularly air conditioning, slightly cool air conditioning maybe a contributor to certain chronic health conditions because [00:19:00] being slightly cold for long periods of time is a stimulus for hunger and may actually drive overeating.
And it’s, it’s one of the reasons why, uh, swimming has been found to be a type of exercise where after you exercise, as you’re more likely to overeat beyond the, the calorie expenditure from the exercise, because you have a decrease in core temperature from spending so much time in, in water that’s below your core temperature.
So this, that’s another way in which The temperature of the environment may be driving mismatch is that that sort of like slightly cold air conditioned type temperature may be messing with things like like satiety signaling. Right? Right. So slightly off from what we’re expecting. Good answer. So another question is, say I’m someone who I’m exercising You know, regularly doing whatever, following, following all the best guidelines there.
Do you, would you still think there’s a case to be made for sauna for health benefits in that particular intervention? So are there, are there things that are above and beyond the benefits that you might get, that you get from, from a good exercise program? Yeah, I was thinking about this and there are a couple of things.
One is that the kind of cardiovascular stress that you get in sauna, I mean, stress in a good way. Mmhmm. It’s probably, it’s like adding additional aerobic training volume to your training program without some of those additional stresses that may sort of get you to the point of diminishing returns.
Like, just say if you’re a runner, extra time pounding the pavements, you know, can be a stress on, you know, other parts of the body so I think there’s, there’s a possibility that you can get. some additional benefits like aerobic exercise without some of the potential downsides that can come from sort of like the stress associated with high, high volumes of aerobic exercise.
So that’s a possibility. And then the other thing is probably sweat related in particular because A lot of people who exercise don’t necessarily sweat a lot when they exercise. I sweat a ton, like, I literally look at, look at some stairs and I start sweating. Yeah, same. But that’s not the case for everybody, so, so I think that it could be particularly beneficial for, for those who, who for whatever reason just don’t sweat a lot when they exercise.
And then another question is if I’m looking to get started sauna with sauna is there, is there sort of a magic zone of dose frequency? , are the benefits front loaded, you know sort of like what’s the kind of the minimum effective dose that at least, you know, I know these are speculations and we don’t have, you know, really great data to draw on, but what’s your kind of best estimate?
Yeah, unfortunately, a lot of the recommendations for like, time and frequency come essentially from this same study, and they, they like, separated groups by, [00:22:00] like, less than 11 minutes per session, and 11 to 19 minutes per session, and more than 19 minutes per session. Those are completely arbitrary, statistical, statistically derived cutoffs that, in my mind, probably don’t mean very much at all but that, those seem to be forming the basis of, of recommended protocols.
Think there’s at least one study where they showed that you acclimate, and Those who are acclimated to heat see a bigger increase in certain heat shock proteins when they’re exposed to heat than those who aren’t regularly exposed to heat, so it suggests that almost, once you’re, once you’ve done more sauna, you may get more benefits from that sauna, that’s, that’s entirely hypothetical based on just, you know, some biochemical responses, but certainly seems, you know, that certainly seems possible that as you acclimate, You may derive more benefit from it.
In reality, it makes sense to me that A session should be something like 15 to 20 minutes at least because that’s how long it probably takes for you to get hot enough to really, you know, get the system working get, get your heart rate up, get your, get your sweat rate up and stimulate adaptation.
Yeah, and stimulate adaptation. So something in that range. Generally when I jump in a sauna, I think 15 minutes is probably the minimum I’d aim for, you know, ideally 20 minutes or longer and that’s just because that’s how long it takes for me to, and so this may be, right, so some people may jump in a sauna and, right, within two minutes your heart rate’s at 120 and you’re just like, sweat is streaming off you, then maybe a shorter period is just fine and I would start with whatever you’re
Great. And see how you feel. I, for a while I tinkered with hot yoga, which is like, so a combination of basically being in a sauna while you do yoga. I loved it. It was great. But, I mean, I probably lost ten pounds in sweat in an hour. So, you know, maybe there’s some ways to, do a bit of both.
If you, if you want to, if you want to do some mobility and some balance, some coordinative movement work, then, you know, maybe hot yoga is a way to get the best of both worlds. That’s something we’re thinking about. Did you enjoy the hot yoga while you were doing it or was it how you felt afterwards that made you both?
Oh, okay. Yeah. I mean, I was. Well, I’m, I wasn’t particularly skilled at yoga, but it’s not, it’s not a skill that I’ve practiced. But I enjoy sweating. So I enjoyed it before and then, or during, and then after is, it was also a very nice feeling. Nice. Great. I think another thing this highlights is, you know, I think one of the things that we advocate for is far more research into these potentially powerful lifestyle based interventions that are falling into quadrant two, and we have a relative, you know, paucity of them, given the potential, like, given the numbers, right?
We see numbers that, whether they are true or not, are pretty remarkable, and certainly worth exploring, like, a lot, right? Like, figuring out what’s the best protocol, how do we individualize it, all that stuff for these kind of interventions that are both likely more powerful and safer than our pharmaceuticals so.
Spending a lot more time and energy and resources into looking into those things. Okay. Well, thank you for that excellent answer, Tommy. Thank you, Dimitri, for your question. If you guys have any other questions for us related to brain health and fitness or follow up questions related to this topic of sauna, send them our way at brainjo.academy/questions.
academy forward slash questions. All right. We will see you guys next time. Thank you, Tommy. Thank you. Thanks, everybody. Bye.