What the sauna studies found

The best-known study followed 2,315 men aged 42 to 60 from eastern Finland for a median of about 21 years. ¹ Compared with men who used the sauna once a week, men who used it 4–7 times a week had about half the risk of fatal cardiovascular disease and a 40% lower risk of dying from any cause during follow-up. ¹ Longer sessions, of more than 19 minutes, were also associated with lower risk of fatal heart disease. ¹

The same study looked at sudden cardiac death and coronary heart disease, and more frequent sauna use was associated with lower risk of both. ¹ These are large differences, which is exactly why they deserve a careful reading rather than a headline.

A later review of the evidence on traditional Finnish saunas, heated to roughly 80–100 °C, describes regular use alongside lower blood pressure, less inflammation and less arterial stiffness. ² The authors suggest that some of the effects resemble those of moderate physical activity. ²

What those studies cannot tell you

The Finnish study is observational. It shows that frequent sauna users had better outcomes, not that the sauna caused them, and the authors called for further studies to understand the link. ¹ It also included only men, in a country where the sauna is part of everyday life. People who feel unwell may also avoid the heat, which could make regular users look healthier than the sauna alone would explain.

The review authors make the same point: well-designed randomized trials with long follow-up are still needed to know whether the associations reflect a true effect, and evidence on the long-term effect of habitual sauna use on blood pressure is limited. ² Treat the sauna as a pleasant habit that may support your heart, alongside training, sleep and food, not instead of them.

How to use a sauna safely

Deaths in saunas are rare. A review of Finnish cases from 1990 to 2002 found fewer than 2 per 100,000 inhabitants a year. ³ Alcohol was involved in about half of the cases, and the authors recommend drinking less and never leaving an intoxicated bather alone in the sauna. ³

The review of sauna research concludes that sauna bathing is safe for most people and can be used even by many people with stable heart disease, when it is used sensibly. ² If you have a heart condition, low blood pressure or any doubt, ask your doctor before you start.

Pregnancy is a clear reason to skip it unless your midwife or doctor says otherwise. Overheating in early pregnancy is associated with a higher risk of neural tube defects in the baby. ⁷

• No alcohol before or during a session.
• Start with one short round and leave as soon as you want to.
• Drink water before and after, and cool down gradually.
• Get up slowly: heat can make you light-headed when you stand.
• Leave straight away if you feel dizzy, sick or unwell.

What cold water can and cannot do

A 2022 review of 104 studies on voluntary cold-water immersion found many reports of measurable effects on the body, and some suggest changes in body fat and better insulin sensitivity. ⁴ The same review notes that most studies are small, often include only men or only women, and use very different water temperatures, which makes firm conclusions hard. ⁴ Whether regular winter swimmers are simply healthier to begin with remains unclear. ⁴

A broad review of cold-water immersion as both a hazard and a treatment reached a similar verdict: the evidence for the many claimed benefits varies a lot, and for some claims it is still at the level of anecdote. ⁵ If you enjoy cold water, that is a good enough reason to do it. Just do not expect it to replace sleep or training.

Cold plunges and your training

Timing matters if you lift. In one study, 21 physically active men did strength training twice a week for 12 weeks and spent 10 minutes either in cold water or doing active recovery after each session. ⁶ The active recovery group gained more strength and more muscle mass, and the authors suggest reconsidering cold water as a regular recovery habit after strength training. ⁶

If strength and muscle are your goal, keep cold plunges away from the hour after your lifting sessions. A cold finish on an easy day, or on a day without strength work, avoids the trade-off.

Fitting heat and cold into a training week

For people who train, the simplest approach is to give heat and cold their own slots instead of stacking them on your hardest sessions. A sauna fits well on easy days, after an endurance session or in the evening as part of winding down. A cold finish fits rest days and easy days, and stays away from the hour after lifting. ⁶

Treat both as extras on top of the work that matters most: training, sleep and food. If a late sauna leaves you wired, move it earlier. If cold water makes you dread the morning, drop it. The habit only helps if it fits your life, and none of it is worth a drink beforehand. ³

Starting cold, safely

The first minute in cold water is the risky part. Sudden skin cooling triggers the cold shock response: a gasp and fast, hard-to-control breathing. ⁵ It can start in water as warm as 25 °C, and the drive to breathe peaks in water of about 10–15 °C. ⁵ The review counts cold shock among the most hazardous responses to cold water, which matters most in open water. ⁵

That is why the safest way to start is the shower at home. Finish a normal shower with 30 seconds of cool water, breathe slowly through the first seconds, and lengthen it only if it feels good. Skip cold plunges if you have a heart condition or high blood pressure unless your doctor agrees, and never drink alcohol before cold water.

• Never swim alone in cold open water, and stay where you can stand.
• Enter slowly and let your breathing settle before you go deeper.
• Keep it short: you are aiming for a calm minute, not a test of will.
• Warm up gently afterwards with dry clothes and a warm drink.

Questions people ask