Heat · Cold · Infrared · Sauna · Recovery · Longevity
These are not rivals. They target different biology through different mechanisms and their evidence bases are distinct. Finnish sauna has 20 years of observational data from 2,315 men. Cold exposure has short-term hormone studies and small trials. Far-infrared has small, short studies in heart failure and little else. Here is what the evidence says about each, graded, and why the sauna vs cold argument misses the point.
The grades in this post: Strong means good randomised trials agree. Mixed means the evidence in people is limited: few, small, short or unblinded trials, or observational studies, which show a link but not proof of cause. Mechanistic means the biology makes sense but it hasn’t been shown to change outcomes in people. None means there’s no usable evidence in people. Temperatures and times below are what the studies used, not advice.
The best-known data come from the Kuopio Ischaemic Heart Disease Risk Factor Study in eastern Finland: 2,315 men aged 42–60, asked about their sauna habits once, between 1984 and 1989, and followed for a median of 20.7 years (Laukkanen 2015). It is observational. Men who use a sauna more often may differ in other ways, and adjusting for known risk factors can’t rule that out.
Over those years, 12.0% of the men who used a sauna 4–7 times a week died of cardiovascular disease, against 16.4% of those who went 2–3 times and 22.3% of those who went once a week; deaths from any cause were 30.8%, 37.8% and 49.1%. After adjusting for cardiovascular risk factors, sudden cardiac death was 63% less likely with 4–7 sessions a week than with one (hazard ratio 0.37, 95% CI 0.18–0.75). For 2–3 sessions it was 22% lower, but that interval (0.57–1.07) includes no difference at all. The paper reports similar patterns for fatal coronary heart disease, cardiovascular disease and all-cause death. Only 201 men were in the 4–7 group, which is why the intervals are wide. Mixed Observational: a large, long study, but a link, not proof.
A later analysis from the same region and research group included women: 1,688 people with an average age of 63, half of them women. After full adjustment, fatal cardiovascular disease was lower with 4–7 sessions a week (hazard ratio 0.23, 0.08–0.65); for 2–3 sessions the interval again included no difference (Laukkanen 2018). Mixed Observational. No randomised trial has tested whether starting to use a sauna lowers deaths.
Sessions a week: once, 2–3 times, or 4–7 times, in a traditional Finnish sauna.
Session length: under 11 minutes, 11–19 minutes, or over 19 minutes. Longer sessions went with fewer cardiac deaths, but not with fewer deaths overall (Laukkanen 2015).
This is what the men said they did, once, at the start of the study. It isn’t advice. If you have heart disease or low blood pressure, or are pregnant, ask your GP before using a sauna.
Cold exposure is better studied for how it makes people feel in the short term than for what it does to long-term health. The best-known hormone study used an hour in 14°C water, far longer than a typical plunge, and it didn’t measure how long the effects lasted.
The full graded picture, including who should be careful, is in Cold Plunges: Who They Help, Who They Harm.
Cold water immersion produces acute cardiovascular stress — cold shock response, vasoconstriction, and the diving reflex produce a rapid rise in blood pressure and cardiac demand. This is contraindicated in: uncontrolled hypertension, recent cardiac events, Raynaud's disease, cryoglobulinaemia, and cold urticaria. Anyone with cardiovascular risk factors should discuss with their GP before beginning regular cold immersion protocols.
After a recent blood clot (DVT), talk to your GP before starting. Cold narrows blood vessels and they widen again as you rewarm; how that affects a recent clot hasn’t been studied. More in Blood Clots: What Raises Your Risk, What Lowers It.
Far-infrared (FIR) saunas heat the body with infrared emitters rather than mainly by heating the air, so the cabin is cooler than a Finnish sauna. This is different from the near-infrared used in red light panels (photobiomodulation), which works at low power without much heating.
Heart failure. Most of the evidence comes from Japan, where a far-infrared treatment called Waon therapy was developed: 15 minutes in a 60°C dry sauna, then 30 minutes resting under a blanket. The longest follow-up is Kihara 2009: 129 people with severe heart failure, 64 given Waon therapy and 65 matched controls, not randomised. Over five years, a heart-failure event or cardiac death occurred in 31.3% of the Waon group and 68.7% of the controls. Eight people died in the Waon group and 12 in the control group; the paper doesn’t say whether that difference is significant. Mixed One small non-randomised study.
Randomised trials exist, but they are short and didn’t measure deaths. In WAON-CHF, 149 people in hospital with advanced heart failure were randomised to 10 days of Waon therapy or usual care. The main measure, the change in a blood marker of heart strain (BNP), didn’t differ significantly; walking distance and symptoms improved in the Waon group (Tei 2016). An earlier two-week study of 188 people, described as randomised, found heart pumping function improved with Waon therapy and not in controls (Miyata 2008). Mixed Short trials; none of deaths or long-term admissions.
Fibromyalgia and arthritis. In 13 women with fibromyalgia, pain roughly halved after Waon therapy, but there was no comparison group (Matsushita 2008). In a Dutch pilot, 17 people with rheumatoid arthritis and 17 with ankylosing spondylitis had eight infrared sauna sessions over four weeks. Pain and stiffness fell during sessions; changes over the four weeks weren’t statistically significant, and there was no comparison group (Oosterveld 2009). I found no randomised trial of infrared sauna itself for either condition; one small Brazilian trial combined far-infrared clothing with pool exercise (Salm 2019). Mixed Small uncontrolled studies.
The consumer market has blurred several distinct technologies under the "infrared" label:
Near-infrared red light panels (630–850nm) — photobiomodulation devices. Mechanism: cytochrome c oxidase photochemistry. Non-thermal. Used at specific doses (mW/cm² × time = J/cm² dose). This is the technology with the most specific mechanistic evidence. See the Sound, Light and Colour Therapy post for detail.
Far-infrared sauna cabins — use FIR emitters (ceramic or carbon elements) to heat the body directly at lower ambient temperatures than conventional sauna. Mechanism: heat. Evidence: small, short studies in heart failure; very little else (above).
Infrared saunas marketed as "full spectrum" — claim to combine near-infrared, mid-infrared, and far-infrared in a single cabin. The near-infrared component in these units is typically at much lower irradiance than dedicated red light panels and is unlikely to deliver the photobiomodulation dose demonstrated in PBM research. The far-infrared part heats you; the photobiomodulation claims are often overstated.
The internet argument between sauna advocates and cold exposure advocates is a category error. These two modalities target different physiological systems through different mechanisms and are not mutually exclusive.
The answer to “sauna or cold?” depends on what you want from it. The Finnish sauna data are the stronger long-term signal, but they are observational. Cold water’s hormone effects are real and short-term as far as anyone has measured; it helps recovery after hard exercise a little, and blunts strength gains if used straight after lifting. Neither has been shown in a trial to prevent disease.
Men in eastern Finland who used a sauna most days had markedly fewer cardiac deaths over 20 years. That’s a strong association, not proof: no trial has tested whether starting to use a sauna changes the outcome.
DunedinPACE estimates how fast you’re ageing from a blood sample. No trial has shown that sauna or cold exposure changes it. If you want a baseline anyway, I’ll go through what it can and can’t tell you.
DH Longevity Investigation →I sell testing, consultations and personal training, so I declare an interest: the article’s grades apply to them too.