What the Finns have always known about sitting very still in a very hot room
Most armies, when they arrive somewhere new, start digging latrines. The Finns build a sauna.
Every nation has its non-negotiable. The French, whatever else is happening around them, will stop for lunch. The Finns, come rain, shine or active military engagement, will have a sauna. To the considerable bemusement of other nationalities, it ranks somewhere between first and second priority on arrival anywhere – and a Second World War field manual recorded this without apparent irony, noting that eight hours is all it takes for a battalion of seven hundred men to build one, heat it and bathe.
The history that followed spans half a century and several continents. In the 1950s, Finnish peacekeepers deployed to the Sinai Peninsula had no materials to speak of, so they jury-rigged a sauna on an abandoned Egyptian military transport platform using telephone poles the Israelis had left behind. On the Golan Heights in the 1980s and 90s, they built saunas for their UN peacekeeping mission and quietly made sure both the Israeli and Syrian ambassadors had access. In Kosovo in the late 1990s – a Balkan summer already running at forty degrees, which most northern Europeans consider quite hot enough – they arrived and built twenty more.
Colonel Matti Ponteva, head of mental health research for the Finnish armed forces, stood outside a pinewood sauna incongruously wedged between grey prefabricated huts in Lipljan and explained the logic as though it were the most self-evident thing in the world. When a squad comes back from a tense situation – coming under fire, finding bodies – they go in together. “That’s the place where they discuss it,” he said. “The steam does what the formal debrief cannot quite manage.”
When Finland joined NATO in 2023, the alliance’s Brussels headquarters promptly installed a sauna. Of course it did.
The Finnish Advantage
Finland has around three million saunas for a population of five and a half million. They are in apartments, on lakesides, in offices. The Finnish parliament has one. For Finns, the sauna is simply what you do – as unremarkable as dinner, as non-negotiable as sleep.
It has taken the rest of us rather longer to catch up, but we’re getting there. Sauna culture has been quietly colonising Britain – boutique bathhouse chains, urban wellness clubs, garden cabin companies with three-month waiting lists – and for once, the science is keeping pace with the trend rather than scrambling behind it.
Strip away any mysticism and a sauna is, at its simplest, a very hot wooden room – kept between 70°C and 100°C, with walls and benches usually built from spruce, which insulates well and doesn’t get unpleasantly sticky in the heat. Lava stones sit on top of the heater, soaking up warmth and releasing it steadily. When you pour water over them – the Finns call the resulting cloud of steam löyly – you’re not actually raising the temperature. You’re adding a brief hit of humidity that makes the heat feel softer and more enveloping. Intense, but bearable. The sauna is, in that sense, more forgiving than it looks from the outside.
What it does to your heart
The cardiovascular benefits of regular sauna use are now well-established – and the numbers, when you see them, are striking.
The key study is the Kuopio Ischemic Heart Disease Risk Factor Study, run by the University of Eastern Finland and published in the prestigious JAMA Internal Medicine. Researchers followed 2,315 middle-aged Finnish men for nearly 21 years, tracking their sauna habits alongside their health outcomes. The pattern that emerged was clear: the more often the men used a sauna, the longer they lived. Those who went two to three times a week had a 24 per cent lower risk of death than those who went once. Those who went four to seven times a week had a 40 per cent lower risk. Time in the room mattered too – men who spent 19 minutes or more per session had a 52 per cent lower chance of dying from heart disease than those who kept it under 11 minutes.
Why? Because the heat makes the heart work harder – in much the same way a brisk walk does. Blood vessels widen, circulation increases, blood pressure drops. Done regularly, this appears to keep the arteries more flexible and the heart in better condition over time. A later follow-up extended the same findings to women, with similar results.
Alongside this, a 2022 study published in the European Journal of Epidemiology identified something important about how the sauna does its work: it reduces chronic inflammation. This matters because low-grade, persistent inflammation sits at the root of most serious long-term illness – from heart disease to diabetes to cancer. The sauna, it turns out, is quietly addressing one of the body’s most fundamental problems.
What it does to your brain
This is where the more recent research gets particularly interesting – and, for many of us at a certain stage of life, rather relevant.
The same Kuopio researchers published a follow-up study in 2017 looking specifically at dementia and Alzheimer’s disease. Their findings were remarkable: men who used a sauna four to seven times a week had a 66 per cent lower risk of dementia and a 65 per cent lower risk of Alzheimer’s disease compared with those who went once a week. These are significant numbers by any measure.
In 2020, a much larger Finnish study – nearly 14,000 men and women, tracked for up to 39 years – confirmed the protective effect and added some useful detail. Sessions of five to fourteen minutes at temperatures between 80 and 99°C appeared to be the sweet spot. Above 100°C, the protective effect disappeared and risk began to edge upward – a reminder that this is a question of regular, moderate use rather than endurance.
The mechanism became clearer still in 2022, when researchers found that the mild rise in body temperature during a sauna session suppresses the build-up of tau protein in the brain. Tau accumulation is one of the key processes driving Alzheimer’s disease – which suggests the sauna may be doing something genuinely protective at the level of brain chemistry, not simply reducing risk factors indirectly.
What is happening at the cellular level
For anyone drawn to the longevity science, there is a further layer to this – and it concerns something called heat shock proteins.
When the body is exposed to heat stress, it responds by producing these proteins, whose job is to act as a kind of internal quality control. They move through the cells identifying damaged or misshapen proteins, repairing what they can and clearing out what they cannot. The process by which cells break down and recycle this damaged material is called autophagy – the body’s own housekeeping system. Research now identifies the gradual failure of this process as one of the primary drivers of biological ageing.
The numbers on heat shock protein production are striking. One study found that thirty minutes in a heat chamber produced a 49 per cent increase in a key variant. A later study found that a sustained period of heat therapy raised two further variants by 45 and 38 per cent respectively, while the cells’ energy-generating capacity improved by around 28 per cent alongside. In plain terms: the heat prompts the body to repair and renew itself at a cellular level. The Finns, who have been sitting in hot rooms for two millennia without once describing it as cellular maintenance, have been doing this their whole lives.
The weight of the evidence
In 2023, Mayo Clinic Proceedings – not a publication given to overstatement – reviewed all available research and concluded that regular sauna use reduces the risk of hypertension, cardiovascular disease, dementia, and respiratory conditions; improves outcomes in musculoskeletal disorders; and increases lifespan. In early 2024, Dr Jari Laukkanen, the lead researcher on the original Kuopio study, published a comprehensive synthesis of nearly a decade of follow-up work, covering cardiovascular protection, neurological protection, immune function, inflammation reduction and cellular repair.
It is, for something as simple as a hot room, a remarkably coherent body of evidence.
The protocol matters
A sauna is not a hot room you sit in until you feel you’ve earned a glass of wine. The approach is straightforward, but following it properly makes a difference.
Start with five to eight minutes in the heat. If possible, lie down with your feet raised to bench level – this keeps blood circulating evenly rather than pooling in your legs. In the last two minutes, sit upright with feet on the floor to let your blood pressure readjust before you stand. Leave slowly.
The cooling phase is not optional. In Finland this means a lake, or the traditional roll in the snow; in Britain, a cold shower serves perfectly well. Wait at least two minutes after leaving before going under the water, and start at the feet, working gradually upward. This hot-cold alternation is where a significant part of the cardiovascular benefit is generated, training the blood vessels to constrict and dilate efficiently over time.
The standard recommendation is three cycles, with the cooling period lasting at least as long as the heat phase. Between sessions, lie down for ten minutes. Drink water, herbal tea or diluted juice before, during and after. Not alcohol. The body is working considerably harder than it appears.
Who should think twice
Anyone with a heart condition should take medical advice before starting. Those with an infection or a fever should wait until they have recovered – the sauna mimics a fever rather than treating one. Some medications affect the body’s ability to regulate temperature, which is worth checking. And if the heat ever feels genuinely wrong rather than simply intense, leave. The Finns, for all their devotion to the practice, are not martyrs about it.
The longer view
What is striking about the sauna is how little it demands of you. No product to buy. No technique to master. No particular mindset to adopt. You sit in a hot room, you cool down, you repeat. The body – repairing proteins, clearing cellular waste, training the heart, dampening inflammation, protecting the brain – does everything else.
Colonel Ponteva understood this intuitively, standing in the Kosovo sun outside his incongruous pinewood cabin. His soldiers were not there for wellness. They were there because after a hard day in a difficult place, it was simply the thing that kept them healthy. The cardiologists and neurologists are, eight decades on, catching up.
Where to find your sauna
The market for home saunas has matured considerably, with Finnish and Nordic brands now offering beautifully designed options across a range of price points, from traditional barrel saunas to sleek modular indoor cabins. A starting point for the search:
Iglusaun — iglusaun.com Estonian-designed outdoor barrel and pod saunas, exported internationally and consistently praised for build quality and authentic heat performance.
Boat Sauna — boatsauna.com Nordic floating and portable sauna designs for those who want their heat therapy with a view. Increasingly popular for coastal and riverside installations.
The Finnish Sauna Society — sauna.fi The authoritative source for guidance on authentic sauna practice, installation standards and the principles of löyly. An essential reference for serious converts.
The British Sauna Society — britishsaunasociety.org For UK-based readers, the BSS offers a directory of new-wave public saunas, guidance on home installation and a growing community of sauna culture advocates.
SaunaPlace — saunaplace.com A well-stocked resource for home sauna options, accessories and buying guidance across a range of price points.
Key studies: Laukkanen et al., JAMA Internal Medicine, 2015; Laukkanen et al., Age and Ageing, 2017; Knekt et al., Preventive Medicine Reports, 2020; Kunutsor et al., European Journal of Epidemiology, 2022; Kunutsor and Laukkanen, Mayo Clinic Proceedings, 2023; Laukkanen and Kunutsor, Temperature, 2024.
