Dr. Jari Laukkanen on Sauna Use for the Prevention of Cardiovascular & Alzheimer’s Disease
Posted on June 15th 2017 (over 1 year)
This podcast features Jari Laukkanen, M.D., Ph.D., a cardiologist and scientist at the Institute of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio. Dr. Laukkanen has been conducting long-term trials looking at the health effects of sauna use in a population of over 2,000 middle-aged men in Finland. The results? Massive reductions in mortality and memory disease in a dose-dependent fashion at 20-year follow-up."In this study, we found, really, that sauna use was inversely associated with the risk of fatal coronary heart disease events and all-cause mortality." - Jari Laukkanen, MD Click To Tweet
Learn more about Dr. Jari Laukkanen
- Sauna use associated with reduced risk of cardiac, all-cause mortality (PubMed)
- Frequent sauna bathing may protect men against dementia, Finnish study suggests (PubMed)
- Frequent sauna bathing reduces risk of stroke (PubMed)
- Frequent sauna bathing keeps blood pressure in check (PubMed)
- Scientists uncover why sauna bathing is good for your health
- Sauna bathing and systemic inflammation (scholarly).
- Sauna bathing reduces the risk of respiratory diseases: a long-term prospective cohort study (scholarly).
Rhonda: Hello, everyone. I am in Finland, sitting here with Dr. Jari Laukkanen. I'm a little excited to be sitting here with Jari because I've talked quite a bit about his research involving using saunas and how that has been shown to improve cardiovascular health and also improve overall longevity. And, to my knowledge, this is actually...your work is the first research that I've actually seen in humans to show that using the sauna, you know, can improve longevity. Maybe we can start off by talking about this study that you did and published about a year ago, I believe, in "The Journal of American Medical Association," "JAMA," looking at the use of the saunas and sauna frequency and cardiovascular-related mortality and overall mortality rate. So can you tell us a little bit about the study itself?
Jari: Yeah, yeah, yeah. Yeah. Thank you. Our study is based on middle-aged population from Eastern Finland. And at baseline, we measured the use of sauna, how many times per week and how long time per one session and what was the temperature, and on the basis of this information, we have studied the association between the use of sauna and fatal cardiovascular outcomes and mortality. And in this study, we found, really, that sauna use was inversely associated with the risk of fatal coronary heart disease events and all-cause mortality. And, after assessment for other risk factors which have been also measured in this big population-based study, there were still significant association between the use of sauna and these outcomes.
Rhonda: Yeah. So if remember correctly, your study showed that men that used the sauna two to three times a week had a 27% lower cardiovascular-related mortality compared to men that used it one time a week. And men that used the sauna four to seven times a week actually had a 50% lower cardiovascular-related mortality than men that used the sauna one time a week, and that is very robust. So you followed these men for 20 years?
Jari: Yeah, yeah. The total follow-up time was 20 years, and we have annually measured new outcomes, and we have followed carefully from baseline until the end of the follow-up. And, yes, the risk reduction was really, really obvious and clear, yeah.
Rhonda: And you said you adjusted for other risk factors meaning, like, obesity, you looked for people...like obesity, smoking, alcohol, cholesterol, type 2 diabetes, these sort of factors?
Rhonda: If I remember correctly, you also looked at socioeconomic status and physical activity, which is important. So these were all...the data's reflective really of sauna use not, you know, because people that use the sauna tend to also exercise more so, you know, you have to correct for all those other possible confounding factors, which you did. So the cardiovascular rate of mortality, were there certain...like, were you measuring all sorts of different ways people can die from heart failure? Like coronary artery disease? Heart attack? Are there certain, like atherosclerosis? Was that looked out? Was it multiple, different types of...
Jari: Yeah, yeah. There were different kinds of outcomes. There were heart-related like coronary heart disease mortality and, also, sudden cardiac death also one of the outcomes. Then we have overall cardiovascular disease death as an outcome and then, also, all-cause mortality. And there was significant association with all these outcomes.
Rhonda: Right. We'll get to all-cause mortality in just a minute, but I kinda want to talk about the cardiovascular-related mortality. It's so important because I know in the United States, heart attacks are, you know, cardiovascular disease is the number one killer followed up by cancer and then respiratory diseases, but Alzheimer's disease is actually climbing up. In Finland, I believe, cardiovascular disease is also the number one killer, correct?
Jari: Yeah. It is still the one. Yeah.
Rhonda: Yeah, so, you know, if you can do something that lowers your risk by, you know, 50%, I mean, that's very significant. What do you think? I have my own sort of, you know, I've done some reading on how the sauna affects in different vascular functions, but you're a cardiologist, so do you have some sort of...do you speculate on some of the mechanisms by which using the sauna can improve cardiovascular health?
Jari: Yeah. Yeah, we have been studying also these mechanisms, which can be explained to our findings. And one of the most important is the blood pressure because sauna use, long-term sauna use, can decrease blood pressure level. Actually, we have studied in the same population and found that there is a reduction of incident hypertension among those who are using more sauna compared to those who have only, let's say, one session per week. And so blood pressure is really one of the most important factors which can explain the findings.
Rhonda: And do you know why sauna lowers blood pressure? Do you?
Jari: There may be many reasons. We know that it can balance the autonomic nervous system as well and, also, it can improve the vessel function.
Rhonda: Endothelial cells?
Jari: Yeah, endothelial cells. And another thing is that sauna may have some effect on arterial stiffness, and compliance of arteries can improve after long-term sauna use.
Rhonda: Wow. So a lot of these parameters that you just described all also known to be affected by cardiovascular exercise, right?
Jari: Yeah, yeah.
Rhonda: Aerobic exercise. So I have to mention that, like, you know, as someone that uses the sauna, when you sit in the sauna for, you know, a long-enough period of time, your heart rate starts to elevate, as if you were doing cardiovascular work. In fact, I think it's something like 100...
Jari: Twenty or 150.
Rhonda: 150 beats per minute.
Jari: Yeah. It is quite high actually. It's something like a moderate level of physical activity.
Rhonda: So you mentioned the duration, the time people spent in the sauna also was an important factor on the robustness of lowering cardiovascular-related mortality. So people that stayed in the sauna, I believe it was longer than 19 minutes had the most robust effect compared to men that stayed in less than 11 minutes, something?
Jari: Yeah, yeah, yeah. Yeah, the risk reduction can be seen among those who more than 20 minutes per session in sauna. They was a risk reduction among those men.
Rhonda: Yeah. I'm always sort of hesitant to tell people, like, they ask, you know, "Well, how long should I stay in the sauna?" Because on the one hand, you don't want to stay in too long, but you also don't want to not stay long enough to get these important benefits, these cardiovascular benefits. So do you have any, sort of, parameters or guide that, you know, someone that's trying to figure out how long to stay in the sauna in order to get these sort of benefit, how long they should stay in? Probably depends on temperature as well.
Jari: Yeah, yeah. On the basis of this study, we found that 20 minutes could be enough, but at the moment, actually, we're exploring more carefully what could be the time that's needed to stay in the sauna, and it can't be that very short time, let's say 10 minutes or 15 minutes. It's not enough to get all these health benefits, maybe. So we try to clarify what is the optimal time to stay in sauna.
Rhonda: Great. So you're working on those parameters right now. What was the average temperature that the sauna that these men were using? How hot was it?
Jari: It was 79 celsius.
Rhonda: Seventy-nine degrees Celsius? So about 20 minutes in a 79-degrees Celsius sauna was what was important for, at least in the context of the lower cardiovascular-related mortality and also all-cause mortality as well?
Jari: Yeah, yeah. That was our primary finding.
Rhonda: And what was the type of sauna that these men are using? Because this is Finland, right?
Jari: Yeah, yeah. It's Finland, yeah. For us it is clear that it is Finnish dry sauna. Yeah, it's relatively dry.
Rhonda: Relatively dry? So they weren't doing that... What's it called when you dump that water on?
Rhonda: Löyly. So that when you make the humidity you do the löyly?
Jari: Yeah. yeah.
Rhonda: Was that also...
Jari: It was also allowed in the use, yeah.
Rhonda: So the all-cause mortality is also interesting because your study showed that, again, there was a dose-dependent effect where men that used the sauna two to three times a week had a 24% lower all-cause mortality than men using it one time a week. And I believe it was men using it four to seven times a week was a 40% lower all-cause mortality?
Jari: Yeah, it was...yeah, yeah. We're calling those dose-response relation.
Rhonda: Right, yeah. So you're getting ready to publish...a paper was accepted that you're going to publish, which will probably be published by the time this video is published, so that's really exciting. So you found that sauna use is associated with lower Alzheimer's disease and dementia. That is extremely interesting to me because, you know, of my interest in heat shock proteins. So the sauna, one of the most robust molecular mechanisms, you know, that happens upon heat stress. So when you heat-stress the body, what happens is that you activate a signaling pathway called heat shock proteins. They play a very important role in maintaining the three-dimensional structure of a protein, which is important, obviously, for protein's function, but it's also very important for the half-life of the protein.
And when the three-dimensional structure of a protein becomes misfolded because of damage that's occurring, you know, damage that, damage their DNA, the same damage that does that damages these proteins, you know, by-products of normal metabolism. Reactive oxygen species, by-products of, you know, immune activation, these things are damaging our proteins, our DNA, our cells. But heat shock...so when those proteins become damaged, they misfold, and they don't get degraded properly. So when this happens in brain, you know, proteins can start to then aggregate and form these plaques, protein aggregates and plaques. So probably the most well-known one is amyloid-beta 42, which is associated with Alzheimer's disease. But interestingly, heat shock proteins, what their function is inside of the cell is to actually repair a misfolded protein so that it maintains its proper three-dimensional structure again.
So they're basically preventing the protein aggregation, and this has been shown in multiple studies in rodents, in lower organisms. There's been many, many studies, associated studies looking at heat shock proteins and neurodegenerative diseases. So there is a lot of interest in how heat shock proteins may be a therapeutic target for preventing neurodegenerative diseases like Alzheimer's and also Parkinson's disease. And I've always thought, you know, the connection between knowing the sauna activates heat shock proteins, I mean, that's their name, you know? They're activated under conditions of stress, particularly heat stress. So I think that would be a very interesting thing to look at.
Jari: I think there some interesting findings, some acute changes after sauna use.
Rhonda: After just a single session?
Jari: Yeah, single session, in vessel and vessel function.
Rhonda: Oh, wow.
Jari: And also heart rate. There is a gradual increase in heart rate during the sauna, single sauna session.
Rhonda: Yeah, I've noticed that myself.
Jari: Yeah, yeah, yeah. When you stay, let's say, 15 minutes in sauna, it's quite easy. It's not demanding. But after that, it becomes more and more demanding to stay in sauna, and your heart rate will increase.
Rhonda: I know there is a bunch of endocrine factors that increase quite dramatically upon just even a single sauna session, like, for one, growth hormone.
Jari: Growth hormone, yeah, it is, yeah.
Rhonda: Growth hormone goes up, like, 200% or 300%, like, even after a single sauna session.
Jari: Yeah, it's quite much, yeah, yeah.
Rhonda: And growth hormone, you know, it plays an important role in preventing muscle atrophy, which is also linked to longevity, right? The more muscle mass you have and more muscle strength is associated with lower all-cause mortality, so that would be interesting to see if that's also related. Do you have any thoughts on whether or not, like, someone who is doing physical activity like doing some kind of a workout exercise, whether they should use the sauna before or after their workout?
Jari: This is very interesting question to see if there's even more clear effects on vessel function and so on if you have an exercise before and then you go to sauna. Actually, we're normally doing that quite often in Finland.
Rhonda: So you normally do the sauna after exercise, after a workout?
Rhonda: Yeah, that's what I do as well, you know? And if you think about it too, it's also the perfect time to get that growth hormone boost, you know, because you've just worked your muscles, so you need that repair, and also the exercise primes your muscles to take in the growth hormone, take in actually IGF-1, which is downstream of growth hormone. So your IGF-1 goes in muscle tissue and also into the brain. So the exercise sort of primes that IGF-1 that's released downstream of growth hormone from the sauna to go into the brain, where it plays a role in actually helping BDNF, brain-derived neurotrophic factor, in growing your neurons. So it's always sort of a question, like, do you do it before a workout or after? And I've always been inclined to do it after a workout, but it would be interesting to know if there's, you know, specifically, if it's affecting, you know, vessel function or things like that.
Jari: Yeah, yeah. We're very interested to see the effects on vessel function after exercise which is combined with sauna and what are the parameters, what are the values after that? And because there are also some evidence that maybe after a strength training, you know, it can be even that the arterial stiffness may increase a bit maybe in some cases.
Rhonda: Oh, really, after strength training?
Jari: So if you go to sauna, you can relax and improve your vessel function also.
Rhonda: Wow, that's interesting. So maybe better to do the sauna after strength training also because...
Jari: Yeah, yeah, yeah. But, yeah, this is, we have no...
Rhonda: You're speculating.
Jari: Speculating, yeah, yeah.
Rhonda: You're speculating, of course. Yeah, yeah, I mean, but it's okay to speculate. Speaking of speculating, so something else that I find very interesting is the effect on mood. Actually, it's what got me interested in the sauna in the first place. So when I was in graduate school, I was very stressed out, you know, exams and failed experiments and lots of pressure, so I was using the sauna and it noticeably improved my mood and helped me deal with stress. It helped me deal with the anxiety I was experiencing. And there is a lot of, sort of, speculative reasons, I think, that's possible, but one is related to cardiorespiratory fitness. So there's actually been studies, one very recently done, published, in a very large sample of people, I believe it was like a million people, looking at cardiorespiratory fitness and depression. And the study found that people with poor cardiorespiratory fitness had a 75% increased chance of being...have been, you know, diagnosed with depression. So I'm sort of interested in...clearly the sauna is affecting, you know, cardiovascular health. And do you know, like, cardiovascular fitness would be, you know, one way to...a measurement of cardiovascular health. Have you ever looked at cardiorespiratory fitness?
Jari: Yeah, we have been measuring, also, cardiorespiratory fitness in our study also in this new study path we have measured, and we can see if there's association between the fitness, and sauna use, and these different parameters. Yeah, yeah.
Rhonda: So that's ongoing right now?
Jari: Yeah, ongoing in our population-based study, although we have adjusted for the level of fitness, yeah, there are also independent associates between the use of sauna and outcomes.
Rhonda: Oh, cool. So but you're saying, you know, in addition to people, obviously, that are physically active, you're adjusting for that, and they're trying to look just specifically at how the sauna may, in and of itself, affect cardiovascular fitness.
Jari: Yeah, itself.
Rhonda: That will be really great. I look forward to that. The other one which I won't get into too much detail because I don't want to talk so much, but it affects endorphins. So sauna releases endorphins. Endorphins make you feel better.
Jari: Feel better, yeah, yeah. It's relaxation, yeah, yeah. Also, in Finland, I think quite many use it for that purpose. They want some relaxation, you know, after working day and so on. It's like a happy to end your day and go to sauna and after that you feel more relaxed.
Rhonda: Do you think that may also have to do with the improved longevity? Because stress is also linked to longevity, and so if it's something that's lowering stress and making you more relaxed, that seems like it goes hand-in-hand with longevity as well.
Jari: Yeah, it can be. There are studies showing the role of autonomic nervous system and cardiovascular diseases, how they are related together. And also in our study we want to explore how the sauna may have effect on heart rate and heart rate variability, which is one of the measures that can be used to assess the autonomic nervous system and its function.
Rhonda: Oh, great. Having been in Finland now for a few days and having the privilege of going to The Finish Sauna Society and also hanging out with some other friends here in Finland, I've had a chance to experience the sauna culture, the traditional smoke saunas, and also the other, you know, dry saunas and the Löyly.
Jari: Löyly, yeah.
Rhonda: But what I also noticed is that almost a 100% of the Finnish people that use the sauna, after the sauna, like to go run into a jump into a cold lake or the Baltic or something cold, very, very cold. And they do this, you know, several times. I mean, it seems to be a very normal part of Finnish sauna culture. Is that accurate, you would say?
Jari: Yeah, yeah. Many people are using. I know it, yeah, yeah.
Rhonda: So I have a question on whether, you know, what is the safety? Is there any safety issues? Because I've read a couple of case reports where because you're going from hot sauna where vasodilation is occurring and then you're going into cold where vasoconstriction is occurring, norepinephrine is being released and vasoconstriction is occurring. There have been a couple of documented cases of, like, coronary artery spasm, I think it's called. Maybe do you think there is a potential risk of going from hot to cold in terms of people with maybe a pre-existing heart disease or something?
Jari: Yeah, among those patients who have coronary heart disease and, especially if it's not stable condition then you have to be very careful. You cannot do that because there can be a spasm in the coronary artery, so it can be harmful, yeah.
Rhonda: But for the most part of the population, it seems to be pretty safe. I mean, I've done it before, and it feels really good. I mean, you feel amazing after doing the hot and cold. Also interested in if it blunts any of the positive effects, but what's interesting is I've seen that cold also activate heat shock proteins because heat shock proteins are part of the stress response, you know? It's called hormetic stress. Are you familiar with hormesis?
It's like a little bit of good stress where it's not too much stress, but it's enough stress to activate all of these genetic pathways that help you deal with stress. Well, heat shock proteins are one of those genetic pathways. And so cold is also a little bit of a hormetic stress, and exercise activates heat shock proteins as well. But heat robustly activates them, very robustly. It's good to know that both the hot and the cold are activating some of the same good genetic pathways. So maybe you're not negating all the good stuff you just did with the sauna, right? Maybe there's synergy.
Jari: We would be really happy to investigate those possible mechanisms between sauna and memory disease, because we have been thinking through, you know, more like improve cardiovascular system, and circulation, and these, if they have a effect on the memory diseases because some cardiovascular diseases and memory diseases are sharing the bit similar risk factors.
Rhonda: Yeah, like vascular dementia. Of course, yeah, blood flow is absolutely linked to dementia. So there's probably multiple mechanisms by which the sauna...
Jari: Multiple mechanisms, yeah.
Rhonda: Man, it's great. We gotta get the word out there, you know, more research, more people using the sauna. I think that's...
Jari: Because I think nowadays there are so many studies showing the positive effects of physical exercise on these outcomes and vessel function and so on, but there are quite limited data on sauna use, and warm exposure, and these similar outcomes, so there are space to do this kind of research.
Rhonda: Yeah. You're like, you know, an explorer in new territory, and no one is really doing this, you know, and it's really great. I'm very glad that someone is, you know, so please keep up the good work.
Jari: And in the best case, of course, we can combine these positive effects in, like, exercise and sauna.
Rhonda: Exactly. Are you going to look at that as well? Are you going to see if there is a synergy?
Jari: Yeah, yeah, we try to do something, yeah. What is also important for public health level that also we have to emphasize that there many other factors in addition to exercise and sauna, there are other also. Of course, we have to take care of other risk factors like blood pressure, lipids, smoking, obesity in addition to that.
Rhonda: Yeah. Cool. Well, Jari, thank you so much for taking time to speak with me and I know you're on Twitter. I follow you on Twitter. Do you want to say your Twitter handle name because it's your name backwards, I think?
Jari: Yeah. You're welcome to follow, yeah.
Rhonda: Can you spell it out for people?
Jari: Jari Laukkanen.
Rhonda: Right, but your Twitter handle is LaukkanenJari, I think. So, yeah, L-A-U-K-K-A-N-E-N-J-A-R-I. That's your Twitter handle, yeah. Okay, excellent. Well, thank you again, Jari.
Jari: Thank you. Thank you so much.
Rhonda: Special thanks to Dr. Laukkanen for meeting with me, and for even making special allowances for my unpredictable schedule while I visited Finland, allowing me to drop in his home late in the evening for a quick conversation. If you want to learn more about the effects of the sauna on cardiovascular disease, Alzheimer's disease, all-cause mortality, exercise performance and muscle mass, get on my email newsletter. I send out great articles not only on these topics but many other topics as well. You can find that newsletter sign-up as well as a longer informative report on sauna use on my website at foundmyfitness.com. Also, a special thanks to my crowd supporters. It's ultimately their pay-what-you-can monthly pledges that help me have the resources to keep the ball rolling. If you're interested in supporting the channel for as a little as a cup of coffee or whatever amount you like, head over to findmyfitness.com/crowdsponser.
All of the deaths that occur in a population, regardless of the cause.
A protein present in the human brain, found primarily at the synapses – the junctions between neighboring neurons where the exchange of electrical signals and neuronal communication occurs. Aggregation, or clumping, of alpha-synuclein proteins is a hallmark of Parkinson's disease, a neurodegenerative disorder of the central nervous system. **Hsp70, a heat shock protein, has been shown to reduce formation of alpha-synuclein oligomers and reduce associated toxicity**.  Danzer, Karin M., et al. "Heat-shock protein 70 modulates toxic extracellular α-synuclein oligomers and rescues trans-synaptic toxicity." _The FASEB journal_ 25.1 (2011): 326-336.
Amyloid-beta (a-beta or amyloid-beta 42)
A toxic 42-amino acid peptide that aggregates and forms plaques in the brain with age. Amyloid-beta is associated with Alzheimer's disease, a progressive neurodegenerative disease that can occur in middle or old age. Alzheimer's disease is the most common cause of dementia. Insufficient sleep increases the production of amyloid-beta, and amyloid-beta deposition, in turn, impairs sleep. **Heat shock proteins have been shown to inhibit the early aggregation of amyloid beta 42 and reduce amyloid beta plaque toxicity**.  Wu, Yanjue, et al. "Heat shock treatment reduces beta amyloid toxicity in vivo by diminishing oligomers." _Neurobiology of aging_ 31.6 (2010): 1055-1058.
An index of the elasticity of large arteries such as the thoracic aorta. Arterial compliance is an important cardiovascular risk factor which diminishes as a function of age and systolic blood pressure. Arterial compliance is measured by ultrasound as a pressure (carotid artery) and volume (outflow into aorta) relationship.
A disease characterized by the deposition of fatty plaques on the inner walls of arteries. Something is said to be **atherogenic** when it promotes the formation of fatty plaques in the arteries. _Atherosclerosis causes **coronary artery disease**._
Autonomic Nervous System
A division of the peripheral nervous system that influences the function of internal organs, and acts largely unconsciously to regulate bodily functions such as the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal. **It is also the primary mechanism in control of the fight-or-flight response and the freeze-and-dissociate response.**
Brain-derived neurotrophic factor (BDNF)
A type of protein that acts on neurons in the central and peripheral nervous systems. BDNF is a type of neurotrophin – or growth factor – that controls and promotes the growth of new neurons. It is active in the hippocampus, cortex, cerebellum, and basal forebrain – areas involved in learning, long term memory, and executive function. **Exercise in combination with heat stress increases BDNF more effectively than exercise alone**.  Goekint, Maaike, et al. "Influence of citalopram and environmental temperature on exercise-induced changes in BDNF." _Neuroscience letters_ 494.2 (2011): 150-154.
Cardiovascular disease (CVD)
A large class of diseases that involve the heart or blood vessels, including stroke, hypertension, thrombosis, heart failure, atherosclerosis, and more. Cardiovascular disease is often caused by lifestyle factors. As such, up to 90 percent of cardiovascular disease may be preventable .  McGill, Henry C., C. Alex McMahan, and Samuel S. Gidding. "Preventing heart disease in the 21st century." _Circulation_ 117.9 (2008): 1216-1227.
In statistics, a confounder (also confounding variable or confounding factor) is a variable that is correlated (directly or inversely) to both the dependent variable and independent variable.
Coronary artery disease (CAD)
also known as ischemic heart disease (IHD). a group of diseases that includes: stable angina, unstable angina, myocardial infarction, and sudden cardiac death. In 2015 CAD affected 110 million people and resulted in 8.9 million deaths. **It makes up 15.9% of all deaths making it the most common cause of death globally.**
Describes the change in effect on an organism caused by differing levels of exposure (or doses) to a stressor. Studying dose response, and developing dose–response models, is central to determining "safe", "hazardous" and (where relevant) beneficial levels and dosages for drugs, pollutants, foods, and other substances to which humans or other organisms are exposed.
The lining of the interior surface of blood vessels and lymphatic vessels, which forms an interface between circulating blood or lymph in the lumen and the rest of the vessel wall. Endothelial dysfunction is a systemic pathological state of the endothelium broadly defined as an imbalance between vasodilating and vasoconstricting substances produced by (or acting on) the endothelium. This is a major physiopathological mechanism that leads towards coronary artery disease, and other atherosclerotic diseases.
Heart Rate Variability (HRV)
The physiological phenomenon of variation in the time interval between heartbeats. It is measured by the variation in the beat-to-beat interval. Decreased parasympathetic nervous system activity or increased sympathetic activity will result in reduced HRV. Reduced HRV has been shown to be a predictor of mortality after myocardial infarction, and a range of other outcomes/conditions may also be associated.  Kleiger, Robert E., et al. "Decreased heart rate variability and its association with increased mortality after acute myocardial infarction." _The American journal of cardiology_ 59.4 (1987): 256-262.
Heat shock protein
A family of proteins produced by cells in response to exposure to stressful conditions. Heat shock proteins are expressed in response to heat as well as exposure to cold and UV light, and during wound healing and tissue remodeling. Many heat shock proteins function as chaperones by stabilizing new proteins to ensure correct folding or by helping to refold proteins that were damaged by cell stress. **A 30-minute 73ºC sauna session in healthy young adults has been shown to cause a robust and sustained increase in the production of heat shock proteins for up to 48 hours afterward**.  Iguchi, Masaki, et al. "Heat stress and cardiovascular, hormonal, and heat shock proteins in humans." _Journal of athletic training_ 47.2 (2012): 184-190.  Iguchi, Masaki, et al. "Heat stress and cardiovascular, hormonal, and heat shock proteins in humans." _Journal of athletic training_ 47.2 (2012): 184-190.
The term for generally-favorable biological responses to low exposures to toxins or other stressors such as exercise, heat stress, fasting, and **xenohormetics**. Examples of xenohormetic substances include plant polyphenols – molecules that plants produce in response to stress. Some evidence suggests plant polyphenols may have longevity-conferring effects when consumed in the diet. Compounds like polyphenols are beneficial, in part, because they trigger mild cellular stress that induces beneficial stress response pathways.
Hypertension Also known as high blood pressure. Long term high blood pressure is a major risk factor for coronary artery disease, stroke, heart failure, peripheral vascular disease, vision loss, and chronic kidney disease. About 90–95% of cases are primary, defined as high blood pressure due to nonspecific lifestyle and genetic factors. The remaining 5–10% of cases are categorized as secondary high blood pressure, defined as high blood pressure due to an identifiable cause, such as chronic kidney disease, narrowing of the kidney arteries, an endocrine disorder, or the use of birth control pills. Lifestyle factors that are known to increase the risk include excess salt, excess body weight, smoking, and alcohol.
Insulin-like growth factor 1 (IGF-1)
One of the most potent natural activators of the AKT signaling pathway, stimulator of cell growth and proliferation, potent inhibitor of programmed cell death, primary mediator of the effects of growth hormone, and has been implicated in contributing to aging and enhancing the growth of cancer after it has been initiated. Similar in molecular structure to insulin, IGF-1 plays a role during childhood for growth and continues later in life to have anabolic, as well as neurotrophic effects. Protein intake increases IGF-1 levels in humans, independent of total caloric consumption.
The steam that rises from the sauna stove (kiuas) or the heat of the sauna.
The 3-dimensional structure of a protein. The structure of a protein is determined by its amino acid constituents, the interaction of its amino acids with each other, and the interaction of its amino acid constituents with the environment surrounding the protein. The conformation then determines how the protein functions and how long its half-life is.
Reactive Oxygen Species (ROS)
Oxygen-containing chemically-reactive molecules generated by oxidative phosphorylation and immune activation. ROS can damage cellular components, including lipids, proteins, mitochondria, and DNA. Examples of ROS include: peroxides, superoxide, hydroxyl radical, and singlet oxygen. A related byproduct, **reactive nitrogen species**, is also produced naturally by the immune system. Examples of RNS include nitric oxide, peroxynitrite, and nitrogen dioxide. The two species are often collectively referred to as **ROS/RNS**. Preventing and efficiently repairing damage from ROS (**oxidative stress**) and RNS (**nitrosative stress**) are among the key challenges our cells face in their fight against diseases of aging, including cancer.
Sudden cardiac death
Death from a sudden stop in effective blood flow due to the failure of the heart to contract effectively (known as **cardiac arrest**). Some people may have chest pain, shortness of breath, or nausea before this occurs. The average percentage of people who survive cardiac arrest with treatment is about 8%. Sudden cardiac death accounts for about 15% of all death in Western countries.
An endogenous opioid neuropeptide used as an analgesic in the body to numb or dull pains that has also been implicated in thermoregulatory mechanisms, increasing significantly in response to heat stress. Endorphin is a contraction of "endogenous" and "morphine." On a molar basis, the analgesic potency of its effects are up to 33-times more potent than morphine. Both morphine and β-Endorphin act on the μ-opioid receptor. Interestingly, the hormonal milieu involved in the bodily response to hyperthermic stress is impaired to varying degrees in a variety of substance abuse conditions, including alcoholism, heroin, and cocaine addiction.  Ježová, Daniela, et al. "Rise in plasma β-endorphin and ACTH in response to hyperthermia in sauna." Hormone and Metabolic Research 17.12 (1985): 693-694.  Loh, Horace H., et al. "Beta-endorphin is a potent analgesic agent." Proceedings of the National Academy of Sciences 73.8 (1976): 2895-2898.  Vescovi, P. P., et al. "Hyperthermia in sauna is unable to increase the plasma levels of ACTH/cortisol, ß-endorphin and prolactin in cocaine addicts." Journal of endocrinological investigation 15.9 (1992): 671-675.
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