Taking a hot sauna regularly can feel good and relax you, but can it also prevent heart disease and Alzheimer’s disease? If you’re from the US, you probably associate saunas with gyms and spas. But saunas have existed in some form for hundreds of years, particularly in Scandinavia, where they are used regularly as part of the culture. Nowhere are they more ubiquitous than in Finland – it is estimated that 99% of Finns use one at least once per week. Saunas have traditionally been used as places to relax with friends and family and to recover from intense physical activity. And while sauna usage is typically associated with health behaviors (like using a sauna after exercise or before sleep as a way to relax), researchers have now taken a closer look at sauna health benefits.
In the latest episode of humanOS Radio, I talk with Jari Laukkanen, MD, Ph.D. Jari is a clinical cardiologist who runs a research lab at the University of Eastern Finland. He primarily studies the role of a wide range of measurable risk factors in relation to cardiovascular disease.
Much of his work has used data from the Kuopio Ischemic Heart Disease Risk Factor Study (KIHD), an extensive epidemiological research project that has followed nearly 3,000 men living in eastern Finland. This population has been identified as having among the highest rates of cardiovascular disease in the world, so figuring out disease prevention strategies has been a target of health researchers for several decades.
He and his group recently conducted a study that used this population to investigate sauna health benefits – specifically, whether sauna use might influence brain health and cognitive decline with aging. Let’s have a quick look at what they did.
Sauna Health Benefits: Study Design
The study examined a random sample of 2,315 middle-aged Finnish men (participating in KIHD) over the course of two decades. Participants were divided into three different groups, based on their sauna habits:
- Those who used the sauna once per week.
- Those who used the sauna 2 to 3 times per week.
- Those who used the sauna 4 to 7 times per week.
An average sauna session for this population, by the way, was about 15 minutes. So this wasn’t quite as big of a time commitment as you might think, at least for most people in the study. So, what were the sauna health benefits?
Sauna Health Benefits: Study Findings
Men who used saunas more frequently had a lower risk of dementia at the end of the study period. In fact, the benefits were most pronounced for those who used sauna almost every day: Men who used saunas 4 to 7 times per week had a 66% lower risk of dementia and a 65% lower risk of developing Alzheimer’s disease compared to those who only used saunas once per week.
Interestingly, Jari and his group found in a previous study that sauna bathing is also associated with reduced risk of cardiovascular disease and all-cause mortality.
In the interview below, I speak with Jari about interesting details of his research, and we explore possible reasons why saunas might be producing these remarkable health benefits. Many health benefits seem to come from regular exposure to mild stressors (like heat exposure, cold exposure, exercise, sun exposure, xenohormetic plant compounds like phenols, and fasting). Also, after you listen to my interview with Jari, you can find more analysis on the health benefits of regular sauna usage from my colleague Dr. Rhonda Patrick (aka FoundMyFitness) here and here.
Return of the Bathhouse
So, sauna bathing may not just be relaxing, it may help you to stay youthful and live longer. Because of this, I’m really pleased to see the bathhouse making a resurgence in and around Silicon Valley. Just recently, for example, a chic bathhouse called Onsen opened in the Tenderloin region of San Francisco. While my conversation with Jari focuses on the health benefits of heat acclimation, there very likely are other health benefits of connecting with a community in a relaxing and technology-free zone. Here is an excellent article by Jon Stein entitled It’s Time to Reconnect: The Return of the Bathhouse which explores these other ideas in more detail.
Dan Pardi - 00:06: Some frequencies inversely are associated with the risk of dementia and Alzheimer's disease, which means that if you're more saunas you're at lower risk of these diseases. The highest risk reduction, which is over 60 percent, was among those who had 4-7 times sauna per week.
Kendall Kendrick - 00:29: Human OS. Learn. Master. Achieve.
Dan Pardi - 00:39: Professor Jari Laukkanen, welcome to Human OS radio.
Jari Laukkanen - 00:42: Thank you, thank you.
Dan Pardi - 00:43: Tell me about where you work and the type of research that you do.
Jari Laukkanen - 00:46: I work in a hospital as a cardiologist, basically I am focused on invasive cardiology in hospital work, but my research work is more focused on epidemiological studies.
Dan Pardi - 00:58: And you recently published a study in the December issue of the journal "Age and Aging" looking at sauna usage and risk for dementia. And before we discuss that study, tell me about some of the prior research that made you interested to explore this area.
Jari Laukkanen - 01:14: We have done quite a lot of [inaudible 00:01:18] studies on cardiovascular risk factors. My research has focused all on benefits of exercise and cardiovascular risk-relation. So, then, I have been also always interested in what various life risk factors including: also dietary factors, physical activity and sauna is also closely related to physical activity habits in here, in Finland, so, we are more and more interested about the sauna and how the sauna may protect against cardiovascular disease and what is the role of sauna in prevention. So, this is basically my background research before that [inaudible 00:02:00].
Dan Pardi - 01:58: Great, so let's discuss your current study. How was it conducted?
Jari Laukkanen - 02:02: Yes, this is a populous-based study. The study was originally designed to investigate risk factors for cardiovascular outcomes in middle-aged men from eastern Finland. And, in this study, we included middle-aged men aged from 42 to 60 years. And in this study we had a sample of men with a complete assessment on sauna bathing habits and then assessment of baseline characteristics, like smoking, alcohol consumption, blood pressure and many other risk factors. Finally, we also assessed all dementia and Alzheimer's disease cases that occurred during the long-term follow-ups since the baseline study.
Dan Pardi - 02:47: Mm-hmm (affirmative).
Jari Laukkanen - 02:47: So, we have a complete information on sauna bathing habits in 2,300 men in this study.
Dan Pardi - 02:54: And what length of period you have information on this population?
Jari Laukkanen - 02:57: We have quite long follow-up. History was started already in the late 1980's and the baseline study collection was conducted in the beginning of the 1990's and then we have follow-up with respect to these outcomes for every year. Actually, we have annually assessed all outcomes occurred during the follow up. So, now we have a total of 20 years of follow up with all these main outcomes including memory diseases and also cardiovascular disease outcomes.
Dan Pardi - 03:28: So, the study was originally set up to look at aspects of heart disease in over 2,000 men. It's been going on for 20 years. You follow up every year to check up on some aspects of interest related to health. Tell me about the length of time that this population spent in a sauna. So, what's typical for an average session for a Finnish man to be in a sauna?
Jari Laukkanen - 03:49: In this study, an average time in the sauna was 15 minutes.
Dan Pardi - 03:54: Mm-hmm (affirmative)
Jari Laukkanen - 03:55: The correct mean time, standard deviation is 7 minutes. So, the range in sauna time was actually quite wide. It was actually from 2 minutes up to 90 minutes. So, there's a lot of variation in this population. And, referring to frequency ... We assessed, of course, frequency of sauna per week and mean frequency was around 2.1, so basically 2-3 times per week is quite a normal way to use the sauna in Finland. But, there were some who were using it more than 4 times per week, even 7 times per week, using it everyday practically.
Dan Pardi - 04:33: And how hot are these saunas?
Jari Laukkanen - 04:35: They are quite hot. They are saunas, an average temperature is around 80 degrees, sometimes it can be even 90 to 100 degrees even in celsius. The lowest level was around 60 degrees, but an average, as I said, is 80 [inaudible 00:04:51]
Dan Pardi - 04:53: Yeah, to translate that for people who use Fahrenheit, that's a temperature of 176 to about 212 degrees Fahrenheit, so really hot.
Jari Laukkanen - 05:03: Yeah, it is really hot, but I think it is not so bad. It's quite easy to stay there. It is not too hot. It is dry and humidity is good, and yeah, I think it's possible to stay there and sometimes humidity may temporarily increase because people throw water on the rocks. [inaudible 00:05:23] in the sauna the humidity is around 10-20%.
Dan Pardi - 05:27: So, big range in terms of how long people spent in the sauna. You also looked at the frequency that the population would take a sauna. Tell me about your findings.
Jari Laukkanen - 05:36: The main thing is that sauna frequency is inversely associated with the risk of dementia and Alzheimer's disease which means that if you do more saunas, you are at lower risk for these diseases.
Dan Pardi - 05:48: Yeah
Jari Laukkanen - 05:48: There was already some risk reduction on those men who were 2-3 times sauna per week, but the highest risk reduction, which is over 60%, was on those who have 4-7 times sauna per week and they had the highest risk reduction. The results didn't change although we adjusted for factors like age, body mass index, systolic factors, their lipids, smoking, alcohol use and previous diseases like diabetes or heart diseases and still there was similar findings and they didn't change and the risk reduction was very significant.
Dan Pardi - 06:27: There seems to be a dose-response relationship: more reduction with more exposure to sauna.
Jari Laukkanen - 06:32: You can wonder why we didn't have a group without sauna.
Dan Pardi - 06:37: Mm-hmm (affirmative)
Jari Laukkanen - 06:38: Especially in Finland, it is very very uncommon that people do not use sauna at all. So, we are there are only 12 men in this large population who were not using sauna at all. So, in the lights of statistical analysis, it is impossible to include so small group as a reference.
Dan Pardi - 06:58: Oh, wow!
Jari Laukkanen - 06:59: Yeah, this is the reason that we..
Dan Pardi - 07:01: Really part of the culture, wow. So, aside from this really impressive reduction in dementia, what were some of the other health benefits that you found from sauna usage that you found and have reported previously?
Jari Laukkanen - 07:13: Yes, in our previous study, we focused more on cardiovascular outcomes and we studied how frequency and duration were associated with cardiovascular outcomes. These outcomes included sudden cardiac death, fatal coronary heart disease death, fatal cardiovascular disease and all [inaudible 00:07:35] also. And in this study we also had quite consistent results compared to our dementia study. We found that the risk of sudden cardiac death and fatal cardiovascular events was significantly decreased in men who had the sauna more than 4 times per week. There was also very clear risk reduction.
Dan Pardi - 07:56: Mm-hmm (affirmative)
Jari Laukkanen - 07:57: We found that those men who had sauna sessions longer than minutes
Dan Pardi - 08:02: Mm-hmm (affirmative)
Jari Laukkanen - 08:03: So, meaning 20 minutes or more, so they had also decreased risk of sudden cardiac death and fatal cardiovascular events. There was a similar dose response relationship between duration of single sauna sessions and fatal cardiovascular events.
Dan Pardi - 08:20: Did you look at the relationship between exposure time in the sauna and dementia?
Jari Laukkanen - 08:26: In this recent study, we haven't looked at it yet, but we are going to study how the single session may have an effect on the results with respect to memory diseases as well. Our main focus has been the frequency of sauna because the duration may vary also very much and frequency is a very reliable measure for the exposure of sauna. It's even more [inaudible 00:08:54] sauna session.
Dan Pardi - 08:53: Yeah
Jari Laukkanen - 08:53: And it's also average of the duration of single sauna sessions, and so -
Dan Pardi - 08:58: Right.
Jari Laukkanen - 08:59:
Frequency is very accurate compared to duration of single sauna sessions.
Dan Pardi - 09:03: Yeah, that makes sense. So, while you were looking at associations here, can you speculate on some of the potential mechanisms for these benefits? Clearly we are seeing benefits in cardiovascular health and also in brain health, and of course those two are related, but what do you think are some of the reasons why these benefits are occurring?
Jari Laukkanen - 09:20: This is a very interesting area and still we have to speculate a bit, but of course we know that during sauna, heart rate is increased. Heart rate increases can be comparable with at least a moderate level of exercise, so there are effects on the cardiovascular system during the hot sauna. Of course, during sauna there is no muscle work like during the exercise. This is one issue that heart rate is increased and also circulatory function is changed during the sauna session, it's one aspect.
Dan Pardi - 09:57: Mm-hmm (affirmative)
Jari Laukkanen - 09:57: And then there may be also some positive effects on vascular function. Now-a-days there are some studies that have shown that during the warm sauna, there are improvements in vascular endothelium function. Endothelium are in the walls of the vessels and it is improved during the sauna which may be connected to blood pressure.
Dan Pardi - 10:20: Mm-hmm (affirmative)
Jari Laukkanen - 10:21: This way, we can understand that systemic blood pressure may be lower after the sauna and during the repeated sauna, it may have a positive effect or lowering effect on blood pressure.
Dan Pardi - 10:34: Interesting
Jari Laukkanen - 10:35: Yeah. And there are some evidence that sauna may have some positive effects on the autonomic nervous system. So, it is closely related to body relaxation and maybe heart function or heart arrhythmias and this may be one thing also when explaining these findings, but these are speculative as I mentioned.
Dan Pardi - 10:58: Mm-hmm (affirmative)
Jari Laukkanen - 10:58: Then, last but not least, I think it's that some [inaudible 00:11:04] is also the habit that is considered to be very relaxing.
Dan Pardi - 11:09: Yeah
Jari Laukkanen - 11:10: It may be one possible mechanism which may explain our findings, but of course we need much more studies showing these possible mechanisms and to confirm these findings
Dan Pardi - 11:22: Yeah, I'm also interested in how heat exposure can stimulate heat shock proteins and the myriad benefits that that seems to have. And, just for our listeners, heat shock proteins are a large family of proteins and they aid in the cells response to acute stress and a lot of different types of stressors can induce them. For example, in Ramadan fasting, you see the levels of heat shock proteins rise across the Ramadan period. The higher the amount of heat shock proteins in the serum, it associates with lower cardiovascular disease risk.
11:51: One other thing that I found really interesting, a friend of mine, Paul Shaw, who does fruit fly research in St. Louis, he's a sleep researcher, what he found is that the activity of certain heat shock proteins was under the control of different circadian-controlled genes. When he knocked out those genes, it produced less heat shock protein 83 and that made the flies much more intolerant of sleep deprivation. So, that, to me, is very interesting. I always get a lot of questions about, "Is there anything I can do to get less sleep?". I never would encourage people to try to get less sleep. It's possible that regular sauna could make people more resistant to the effects of sleep loss so that it wouldn't have as much of a negative toll on the following day.
Jari Laukkanen - 12:29: Thank you about this comment, it is very interesting also to study heat shock proteins and then [inaudible 00:12:38] really the sleeping quality. I think these people have the experience that when they normally go to the sauna in the evening and after sauna in the next night we have a better quality of sleep
Dan Pardi - 12:52: Mm-hmm (affirmative)
Jari Laukkanen - 12:53: My friends, my parents and many people have said that after sauna, the quality of sleeping is better than without sauna.
Dan Pardi - 13:01: Yeah, it's another effect on sleep. So, not only making you more resistant (potentially) to the effects of sleep loss, it also might enhance the depth of sleep and we know that a drop in core body temperature is important for the initiation of sleep and then across the night, body temperature continues to drop and that is associated with depth of sleep. So, sleep might become more efficient[crosstalk 00:13:20] by sauna usage in the [evening 00:13:22].
Jari Laukkanen - 13:23: [crosstalk 00:13:20] Yeah. It can be that it is interesting, interesting.
Dan Pardi - 13:26: Yeah, very. So, then, this study focused on men. Do you have plans to do more work on the subject including the effects of sauna on women? Culturally, do women sauna as much as men do?
Jari Laukkanen - 13:38: Yes, in [inaudible 00:13:39], yeah. Both are doing in similar ways. I think there are [inaudible 00:13:44] differences [inaudible 00:13:45]. And it is very common in Finland that families are using the sauna because almost every family has their own sauna, it is so common here.
Dan Pardi - 13:56: Mm-hmm (affirmative)
Jari Laukkanen - 13:57: There are not big differences between women and men with using the sauna.
Dan Pardi - 14:02: Mm-hmm (affirmative)
Jari Laukkanen - 14:03: Of course we are interested, and we should study also, how the sauna may be working and how it's related to outcomes related to women. It could be possible to study in our third dataset and secondly we are going to investigate some physiological [inaudible 00:14:22] in smaller populations assessing these parameters before and after sauna in all genders so we can see if the changes during sauna sessions are similar or different between women and men.
Dan Pardi - 14:39: Yeah, I'm really glad to hear more work will be done here
Jari Laukkanen - 14:41: Yeah
Dan Pardi - 14:42: It seems like at this point, with the science, we have a pretty clear opportunity to improve health from a variety of aspects in people, but obviously more work is needed. Is it a part of the culture to do some cold exposure, like a cold plunge, as part of the sauna ritual. In various cultures around the world, if you do sauna, you will go into a cold pool. Is that part of the culture in Finland?
Jari Laukkanen - 15:04: Yeah, it is part of the culture but there are people who like it and also people who don't use it, so there are different kinds of sauna users, but some like the cold. Also during the winter they like to use sauna and they go in the snow or even the water -
Dan Pardi - 15:22: Mm-hmm (affirmative)
Jari Laukkanen - 15:22:
- and then they go back to sauna and they can do it once or two or three times.
Dan Pardi - 15:27: Yeah
Jari Laukkanen - 15:28: But, I think still that it is a minor part of our sauna culture compared to common use of sauna which is without the very cold exposure between the sauna sessions.
Dan Pardi - 15:40: Yeah, interesting. I know I'd like to see if there's an additional benefit to exposing yourself to stress on the other end of the heat spectrum.
Jari Laukkanen - 15:47: Yeah, yeah.
Dan Pardi - 15:48: My suspicion is that there might be.
Jari Laukkanen - 15:50: Yeah
Dan Pardi - 15:51: By the way, since saunas seem to have an effect not dissimilar (in some ways) to exercise, were you able to look at whether there is an additional benefit of sauna exposure to cardiovascular conditioning, whatever sort of physical training people were doing?
Jari Laukkanen - 16:06: Yes. This is part of our future project, yeah.
Dan Pardi - 16:10: Great
Jari Laukkanen - 16:10: Because commonly we do exercise first and then we go in the sauna. It is a very common habit here. In our population study, it is not possible to investigate. So, this kind of [inaudible 00:16:23] if they are exercising before and they immediately call the sauna, but in our analysis we take into account, in general, physical activity habits and still it seems that the sauna had an independent role and association with outcomes.
Dan Pardi - 16:42: Mm-hmm (affirmative)
Jari Laukkanen - 16:42: That is what we can say based on our epidemiological study. Of course, in future, it could be very well to study if there are any benefits if you combine both physical activity or exercise session with sauna.
Dan Pardi - 16:59: And last question, when do people sauna in Finland? Is it typically after exercise? In the morning? Evening? Or is it really just spread any time throughout the day?
Jari Laukkanen - 17:09: I think that it's part of the evening.
Dan Pardi - 17:11: Mm-hmm (affirmative)
Jari Laukkanen - 17:11: We like to use it more during the evening. But, some people like also to go in the morning. There are different kinds of people. So, it depends how they feel it is better. Because I know also some guys who like to start their days going to sauna and then they go to work. And secondly, I think it's quite common that people do some exercise before.
Dan Pardi - 17:35: Mm-hmm (affirmative)
Jari Laukkanen - 17:36: A half-hour or one hour, [inaudible 00:17:37]. And after this they have a sauna and then they goes home and they feel very good after that.
Dan Pardi - 17:46: Sounds good to me!
Jari Laukkanen - 17:47: (laughs)[crosstalk 00:17:46]
Dan Pardi - 17:48: (laughs)[crosstalk 00:17:46]
17:49: Professor Laukkanen, I really appreciate you coming onto the show. I have to admit, I think this is one of the most interesting studies in health application science that came out last year and I am sure that all of our listeners are going to be more interested in using the sauna at their local gym at this point. So -
Jari Laukkanen - 18:04: Yep
Dan Pardi - 18:05:
- thank you for the work that you've done and thank you for continuing to do work in this area. I really look forward to hearing what you find next.
Jari Laukkanen - 18:12: Okay, thank you very much.
Dan Pardi - 18:13: Bye
Kendall Kendrick - 18:17: Thanks for listening, and come visit us soon at humanos.me