Does a sauna lower blood pressure? Short and long-term effects

What happens to blood pressure during a sauna?

In a Finnish experiment, 102 adults with an average age of 52, all with at least one heart risk factor such as high blood pressure or smoking, sat in a sauna at 73°C for 30 minutes. Straight afterwards:

• Average systolic blood pressure (the top number) fell from 137 to 130 mmHg.
• Average diastolic blood pressure (the bottom number) fell from 82 to 75 mmHg.
• Pulse wave velocity, a measure of how stiff the main arteries are, fell from 9.8 to 8.6 metres per second.

Systolic pressure was still lower than at the start after half an hour of rest. Heat widens blood vessels, especially in the skin, and that lowers the resistance the heart pumps against.

Do regular saunas lower blood pressure for good?

The best test so far is a randomised trial in Finland. Researchers took 47 inactive adults, average age 49, with at least one heart risk factor, and split them into three groups for 8 weeks:

1. Exercise to the guidelines, followed by a 15-minute sauna.
2. The same exercise without a sauna.
3. No change.

Exercise alone improved fitness and body fat but did not change blood pressure. The exercise-plus-sauna group improved fitness further and had systolic blood pressure about 8 mmHg lower than the exercise-only group, along with lower total cholesterol. The trial was small and short, but it is the kind of evidence that cohort studies can’t give.

An American trial found something similar with a different way of heating the body. Young inactive adults who sat in hot water up to the shoulders several times a week for 8 weeks had lower diastolic and mean blood pressure, more flexible arteries and better blood vessel function than a group who sat in lukewarm water.

Are frequent sauna users less likely to get high blood pressure?

In the Kuopio study, 1,621 Finnish men aged 42 to 60 who did not have high blood pressure were followed for about 25 years. Compared with men who had one sauna a week, men who had four to seven a week were 47% less likely to be diagnosed with high blood pressure, even after adjusting for fitness, alcohol, income and family history. Two or three sessions a week were linked with a smaller fall that could have been chance.

How big is the effect compared with other measures?

A fall of 7 to 8 mmHg systolic is similar to what many people get from cutting salt, losing weight or taking up regular exercise, and smaller than most blood pressure tablets. A sauna is a reasonable addition to those measures, not a replacement for treatment your GP has recommended.

Who should be careful?

• People on blood pressure tablets, especially alpha blockers, diuretics or several medicines together, are more likely to feel dizzy when they stand up after a sauna.
• People with low blood pressure or who often feel faint on standing.
• Anyone who has been drinking alcohol, which widens blood vessels further. See alcohol and saunas.

The cold plunge that often follows a sauna does the opposite: sudden cold sharply raises blood pressure and heart rate for a short time. If you have high blood pressure, read about cold water shock first.