Infrared Sauna

An infrared sauna heats your body directly with infrared lamps instead of heating the air around you, so it runs at a far more comfortable 50–60 °C. That comfort has a cost: at typical settings it heats you less than a traditional sauna, no long-term study links it to living longer, and most of its trial evidence comes from supervised medical use rather than home cabins.

If you're buying for the longevity evidence, buy a traditional sauna; that is what the evidence was measured on. Choose infrared if comfort is what gets you in, but don't assume it inherits the Finnish numbers. Supervised infrared therapy for stable heart failure is a clinical treatment to discuss with your cardiologist, not a home habit.

A weaker stimulus, not just a less-studied one

A traditional Finnish sauna runs at 80–100 °C; an infrared cabin at 50–60 °C. In one head-to-head comparison, a hot bath raised core temperature most, a traditional sauna less, and a 45-minute far-infrared session not measurably at all.^[1] That is one study, though: run hotter, infrared does produce real heat strain, which suggests the limitation is the dose, not the wavelength.

That matters because the main cardiovascular benefit randomised trials support for heat — a few millimetres of mercury off blood pressure — shows up clearly only with genuine whole-body heating. There are no cohort data on infrared and mortality at all: the long-running Finnish studies behind the famous sauna numbers were about traditional saunas (see The Finnish sauna cohort).

Not a substitute for exercise

Infrared sauna is sometimes sold as "exercise in a box". Tested head to head in a randomised crossover of ten healthy women, an infrared session and a bike ride were not interchangeable: the sauna raised ear temperature more, the exercise raised breathing rate far more, and neither changed blood pressure, arterial stiffness or heart-rate variability compared with rest.^[2]

Nor does it add muscle. In 40 female team-sport athletes split into matched pairs across a six-week strength-and-power block (not randomised), adding infrared sauna after training left every measure of muscle growth unchanged — both groups grew, equally — though loaded jump height and peak power improved in the sauna group.^[3] Two caveats point the same way: the air at hip level was only about 31 °C at 48% humidity, so the heat dose was mild and body temperature was never measured; and the trial was funded by a sauna manufacturer whose own cabin was one of the two units used.

Blood vessels and blood sugar

Waon therapy. This medical protocol is 15 minutes in a 60 °C far-infrared cabin, followed by 30 minutes lying wrapped in blankets — which is where much of the heat load actually comes from. Two weeks of daily sessions improved artery dilation from 4.0% to 5.8% in 25 men with a coronary risk factor.^[4] That was an uncontrolled before-and-after study, not a randomised trial, and it says nothing about traditional sauna.

Blood sugar. In a randomised crossover trial in 12 people with type 2 diabetes, a single 40-minute infrared session did not improve how they handled a meal; the blood-sugar rise afterwards was actually higher than after a control session at neutral temperature.^[5]

Where it has real, modest support: stable heart failure

Decompensated heart failure — when the heart can't keep up and fluid is building — is a reason to stay out of any sauna. Stable chronic heart failure is different. A review of seven unblinded trials in 491 patients found that supervised Waon therapy raised the heart's ejection fraction (the share of blood pumped out with each beat) by 1.45 percentage points, pooled from six of them, lowered a blood marker of strain on the heart and reduced heart size on chest imaging, with no change in blood pressure.^[6] The authors grade their own evidence "moderate to insufficient", the pooled figure leans on small single-centre studies, and the largest and only multicentre randomised trial of the method, in people in hospital with advanced heart failure, missed its main goal.^[7]

This is a supervised add-on to treatment, not a reason for anyone with heart failure to buy a cabin.

Joints and mood

Arthritis. In an uncontrolled pilot study, eight infrared sessions over four weeks in 34 people with rheumatoid arthritis or ankylosing spondylitis (an inflammatory arthritis of the spine) eased pain and stiffness during the sessions and caused no flare-ups. The four-week trends were favourable but not statistically significant.^[8]

Depression. In a double-blind trial of 30 people with major depression, a single infrared whole-body heating session that raised core temperature cut depression scores by about 6.5 points more than a convincing sham at one week, and they were still 4.3 points lower at six weeks.^[9] The closest repeat of that design — infrared whole-body heating against sham in 30 adults all receiving cognitive behavioural therapy — found no advantage: both groups improved by about 20 points, and the sham group slightly more.^[10] These sessions were built to raise core temperature, which a typical cabin may not. A lead, not a treatment.

What to do

Pick the sauna by what you want from it. For the heat stimulus the longevity data is built on, a traditional sauna. For comfort and relaxation, infrared is a reasonable call.
Don't count it as exercise, a muscle-builder or a blood-sugar tool. The trials that tested those found no benefit for those uses.
If you have stable heart failure, ask your cardiologist about supervised therapy rather than starting on your own. If your heart failure is not stable, stay out of all saunas.
The general sauna cautions apply — no alcohol, and the conditions to clear with a clinician first are listed on Sauna.