Association Between Sauna Bathing and All-Cause Mortality Events | Hacker News Reader

Association Between Sauna Bathing and All-Cause Mortality Events

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34 pointsmkempe36 comments

In Finland going to a sauna is often a social activity. You catch up with your best friends in a Friday sauna session. If you use the sauna a lot, maybe it means you have more friends?

There's apparently a connection between social integration and health: http://www.ncbi.nlm.nih.gov/pubmed/23681602

Another uncontrolled-for possibly contaminating factor. There are a host of diseases that make people heat intolerant. Multiple sclerosis (big in Finland) and heart failure are two of them.

People who are relatively intolerant of heat will tend to avoid saunas, thus biasing the outcome in favor of positive health outcomes for people who are able to tolerate the heat.

So they would have had to do a very careful assessment of these people at the time of enrollment in the study.

It's based on a 30-year long longitudinal study of Finnish men, not a miniature people-in-the-sauna "study".

What is the evidence that multiple sclerosis is "big in Finland"?

Good, I live in a Sauna, 8 degrees north of the equator. That bodes well for my health :)

Joking aside, this study seems unlikely to have actually discovered a real effect, rather than just a group of people with lower risk and higher sauna usage in common. (Wealthy people?)

Given that the study was conducted in Finland, it's unlikely that wealth is a confounding factor in sauna usage.

The effect was only noticeable with sauna usage 4-7 times a week, more than wealth that implies free time, which implies lower stress (a risk factor) and, to a degree, wealth.

As always, correlation does not equal causation.

According to the abstract, the effect was significant only at a "dose" of 4 to 7 sauna visits per week in the 20 years of follow-up.

Now, I don't know much about the availability of saunas in Finland, but one must ask: what kind of person can financially afford, or make time for, 4 to 7 sauna visits per week? Even with the statistical adjustment for traditional cardiovascular risk factors, I seriously doubt that the people who use saunas frequently have the same income levels, attention to health, and all sorts of other habits as the people who never use saunas.

So I would put this study on the heap of interesting correlations that ultimately mean nothing.

BTW, they should look at the development of Alzheimer disease. There is suspicion that high body temperatures (e.g. with fever) can incite the changes in protein conformation that are thought to be essential in the establishment and progression of the disease. So, if sauna users stay a little too long, and get a little bit hyperthermic, they may be setting themselves up for Alzheimer disease. That would be a bummer.

Weird train of thought about the supposed scarceness of saunas. My gym in SF has a sauna. Many people use it every time they work out. You can only stay in there for like 10 minutes. Not a huge time investment. Are you telling me that only the very wealthy can afford an $80 monthly gym membership?

Some apartment buildings in Berlin I visited had saunas built in (and these were not luxury buildings).

My understanding is that saunas are even more prevalent in Scandinavia. You should rethink your reasoning.

$80 per month is a lot of money for most people. It's like buying a new pair of running shoes every month. Quite a luxury. This in itself separates groups of people. Reasoning stands.

"""saunas are even more prevalent in Scandinavia. You should rethink your reasoning."""

The cost of access to saunas is not zero in money, and not zero in time. This in itself creates differences between groups, which is why randomized trials are far superior to case-control or observational studies. This is so well established in medicine that there is no cause to rethink the reasoning.

Based on your comments I gather you have never been in Finland. So you know close to nothing about social mores and structures in that country. Your comments are noise, not even wrong.

Correlation means correlation, not that something is impossible. In other words, just because, for example, a poor person can afford to go to sauna 4-7 times a week it doesn't mean that there's no correlation between income level and sauna usage.

Another example would be drinking an "expensive" wine at least once a month. I'd claim that a lot of poor people can afford a $25 wine monthly, but there can still be a correlation between income and buying an expensive wine at least once a month.

A large portion of houses in finland have a sauna - it's as common as a tub (ok, I don't have exact statistics but more or less). Usually in the least apartment buildings have a common sauna. The cost of usage is neglible. Public saunas in swimming halls etc are not very expensive. The income level is not a factor (what ever the quality of the research may be)

I would think it's very uncommon for people living in apartment buildings to go to a sauna 4-7 times a week (I believe that's often not even possible due to various rules). When you add in that there's some correlation between lack of wealth and living in apartment buildings I don't think you can rule out income level that easily.

Well, we are talking about Finland.

http://www.stat.fi/tup/suoluk/suoluk_asuminen_en.html

By the latest numbers there are 1 266 000 residential buildings in Finland, housing 1 581 000 saunas. But of course other buildings also have saunas, so in total there are more than 2 million saunas.

There are 5 451 270 people in Finland.

I'd say a lot of people have access to saunas.

As always, correlation does not equal causation.

The article doesn't claim that it does. That's why the title was specifically constructed to use the phrase "association between" (rather than "causes" or "is caused by.")

What kind of person can financially afford, or make time for, 4 to 7 sauna visits per week?

The kind that has access to a sauna in their own home. Which is quite common in Finland, apparently: "There are five million inhabitants and over three million saunas in Finland - an average of one per household."[1]

[1] https://en.wikipedia.org/wiki/Finnish_sauna

The title is a bit misleading. The abstract states that "significant inverse associations were also observed for fatal CHDs and fatal CVDs (P for trend ≤.03) but not for all-cause mortality events." So going to a sauna 4-7 times a week for these middle-aged Finnish men decreased their chance of dying from a heart attack. But they still might die from something else at the same or somewhat increased rate. I'd argue that the raised heat and humidity in the sauna might have caused an increased workout for the heart. "Shocking" the heart like this almost every day to every other day of the week for twenty years made them more able to survive fatal CHDs and CVDs.

As always, there's trouble with selection bias. Do men who sauna bathe take a more general interest in their health? Do they also eat better, exercise more, have a lower blood pressure etc?

"""After adjustment for CVD risk factors"""

Eating well and exercising are hard to quantify and control for.

It's a good thing all possible CVD risk factors were measured without measurement error, included in the analysis, and had exactly correct coefficients despite sampling error.

It's a good thing we never make any decisions without perfect information.

It's a good thing observational studies like these are not notorious for never replicating and for motivating enormously costly (financially, medically, and personally) fiascos such as the wars on salt and cholesterol.

Is there a way to read the paper without signing up or paying money?

Go nuts.

https://www.dropbox.com/s/2zdys9hzpr6a7ln/ioi140152.pdf?dl=0

I wonder if there are similar cardiovascular benefits for hot tubs. Could it be that it's breathing the hot air in the sauna that's beneficial rather than a general increase in body temperature?

I'm asking because we are thinking about installing a hot tub at some point.

Martin Pall hypothesizes that sauna therapy increases the availability of tetrahydrobiopterin (BH4) through multiple mechanisms [1]. A small study with people with chronic fatigue syndrome provides evidence to confirm this [2] (I don't think this publication is peer reviewed). I believe there is an association between BH4 and cardiovascular health, but this is not my field.

[1] http://www.ncbi.nlm.nih.gov/pubmed/19581054 [2] http://www.townsendletter.com/Nov2013/sauna1113.html

Martin Pall has a history of dubious hypotheses. It seems more likely that it is simply the increase in heart rate that improves cardiovascular health.

Alternating hot and cold showering or even only a cold shower each day, or a few days a week has als been shown to be healthy.

source?

Not sure this proves anything.

People in pain are more likely to seek such relief. People in pain tend to be less healthy and more likely to die soon.

Sauna bathing is associated with reduced risk ;)

yeah, I misread that completely.

Right - that's why the abstract talks of of an "association". Correlation, not causation.

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