If you want to experience positive health effects from sauna, you don't have to set records in heat and duration. You just get hot and sweat as much as you feel is fine. So you can do it in almost all conditions. Sweating out bad stuff from your body, activating the blood flow, unless you are at risk of a aneurysm - of course it is beneficial, even though it doesn't magically turn your health around. But a proper sauna and ice bath do revive and make you feel reborn. Try it at least at some point and then you can judge if it did not make you feel more alive and healthier and that all the studies around it a "probably bullshit".

Also location. In my country, saunas at home aren't as common in Finland, but basically every gym has one. So the people that use the sauna the most, are likely to be the most active.

I don't know about that. As in yes I agree but that seems to apply to Western countries in general. For example in Tunisia, people go to public baths at least once a week and part of that involves sitting in a hot steamy room for 30+ minutes. So here you have an example for a population that does use sauna (in a way) but aren't relying on self-reporting.

As an Estonian, anything below 80°C is considered a "kids sauna". 80°C - 90°C is a cold-but-workable sauna and proper sauna starts from 90+°C. I'd assume it's the same in Finland as we share a lot of the sauna culture.

Also while 73°C is a proper sauna, there are plenty of hotter ones. 90°C is closer to what I'm used to at my apartment building's common sauna. I do take two breaks when I'm there for 30 mims though.

73° hot?

Here in mainland Europe, a "classic fin sauna" is usually at least 90°++

Anything beyond 90 C is not a sauna :) Better to have 90+ and hot steam as in Russian sauna (banya) :)

you can sous vide beef and pork at a lower temperature than that

I'm an immigrant in Scandinavia, originally from a hot country, in my experience a 73C steam sauna is quite tolerable for a 2*15 min session.

The first time I was in a sauna after moving was a bit harder than after getting used to it but doable.

Nowadays I just love them, my friends and I built a couple of saunas to leave by the lake in their summerhouses, the cravings of going from hot -> very cold, and back to the heat is hard to explain, and I totally recommend it.

Northern Spaniard there, bring a Saunaa lover Finn with one of these climate-change induced hours at 43C at some day or two in Summer... in the Atlantic, in Bilbao, which is... inside a valley.

I've been in saunas at 60-70C and the feeling inside was much bearable because of the lack of humidity than 43C under a climate closer to UK than inner/Mediterranean Spain.

Hammam is not as hot as sauna and not as dry. Sauna's air temperatures can reach above 100 degress Celsius and humidity is usually relatively low (around 20%).

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

Hammam's temperatures are around 40-50 degrees Celsius and humidity is close to 100%.

These are very different conditions, with very different body response.

I have not, what is it?

Saunas are very cheap to buy and/or build, certainly within the budget of an average research grant.