Traditional advice is to avoid saunas if you have uncontrolled high blood pressure. This was based on the assumption that heat stress would cause blood pressure to increase. New research suggests that sauna heat helps to dilate blood vessels, promote sweating and relaxation, and reduce arterial stiffness, all of which can help to prevent high blood pressure. The latest evidence suggests that saunas may protect against stroke, too. You should still avoid saunas if your hypertension is not well controlled, however.
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What is sauna bathing?
Sauna bathing is whole body heat therapy that has been practiced for thousands of years. Versions include sweat lodges, Thai dry saunas, Turkish Hammam and Russian Banya, but the most common form is a Finnish sauna in which you have a short exposure (5 to 20 minutes) to a temperature of 80 to 100 degrees Centigrade with dry air (relative humidy 10% to 20%). Humidy is periodically increased by throwing water onto hot rocks. Infrared sauna cabins are also popular and use lower temperatures of 45 to 60 degrees Centigrade, without water to increase humidity. After sauna bathing, you may cool off by plunging into cold water.
Sauna bathing can have profound effects on the body, activating heat regulation pathways in the brain and autonomic nervous system. Sauna bathing increases blood flow to the skin and affects heart rate, salt and fluid balance, hormone secretion and the production of so-called ‘heat shock proteins’ which protect cells from oxidative stress and inflammation.
Saunas may prevent hypertension
Sauna bathing increases your natural production of nitric oxide which causes blood vessels to dilate so blood pressure reduces. A study from Finland followed 1,621 men over the age of 42, who did not have hypertension (defined as a blood pressure of greater than 140/90 mmHg) for almost 25 years. After adjusting for other factors, such as age, smoking, alcohol, glucose levels, fitness, family history of hypertension, income and weight, they found that men who had 2 to 3 sauna bathing sessions per week were 17% less likely to develop hypertension than those having 1 sauna session per week. For those having 4 to 7 saunas per week, the risk was reduced by 47%. The researchers concluded that regular sauna bathing is associated with a reduced risk of hypertension.
They followed up with tests in 100 men to try to find out why, and found that sauna bathing for 30 minutes reduced blood pressure and increased heart rate and blood vessel elasticity in the same way as medium-intensity exercise, while body temperature rose by approximately 2°C.
Immediately after 30 minutes of sauna bathing, average blood pressures reduced from 137/82 mmHg to 130/75 mmHg – a reduction of 7/7mmHg. Thirty minutes later, systolic blood pressure (the upper figure) remained lower compared to before the sauna, too.
Sauna therapy for hypertension
The effects of having a sauna alone or a sauna after exercise (30 minutes on a stationary bike) was tested in 16 people with untreated hypertension. In those who had a sauna alone, there was no significant change, but in those who had a sauna and exercised, systolic blood pressure was 3mmHg higher when measured 2 hours after the sauna (not significant compared to a control period) while in those who had a sauna after exercise, blood pressure was significantly reduced by 8/2 mmHg when measured 15 minutes after the sauna. Blood pressure was back to the pre-sauna readings within 2 hours, however.
Another study involving people with untreated hypertension found that a single sauna session could produce significant changes in nerve control of heart rate and blood pressure, although these changes came back to normal within 15 to 120 minutes. They recommended that additional studies investigated the effects of regular sauna bathing in people with hypertension.
Saunas and blood pressure medication
The effects of a Finnish sauna on blood levels of the antihypertensive drugs, propranolol (a beta blocker) and captopril (an ACE inhibitor) were studied in 8 healthy volunteers who had a sauna bathing session within an hour of ingesting the drugs. Not surprisingly, the fluid loss associated with a sauna significantly increased the maximum concentration of the drugs, but sauna bathing did not lead to significant changes in blood pressure or heart rate compared to the control period (although none of those taking part had hypertension).
Saunas protect against stroke
The Kuopio Ischaemic Heart Disease Risk Factor study, which involved 1,628 Finnish adults aged 53 to 74 years looked for any links between the frequency of taking traditional Finnish sauna baths (relative humidity 10-20%) and stroke. Those who had a sauna 4-7 times a week had a 61% lower risk of stroke than those taking a sauna once a week, while those taking a sauna 2-3 times a week, were 14% less likely to have a stroke than those who only had one sauna a week. This association remained even after taking other stroke risk factors into account, such as age, sex, diabetes, weight, cholesterol levels, alcohol consumption and level of exercise.
Previous results from the same study found that frequent sauna bathing also significantly reduces the risk of cardiovascular and all-cause mortality. Why might the heat of sauna bathing protect against stroke? Suggestions include that it reduces blood pressure, stimulates anti-inflammatory immune responses, or has positive effects on the autonomic nervous system (which regulates blood pressure) and improved cardiovascular function. For example, researchers have found that sauna bathing reduces the stiffness of the artery walls.
Sauna bathing and congestive heart disease
A recent review of 40 clinical studies, involving 3855 people, concluded that regular dry sauna bathing has potential health benefits. Of these, nine studies researched sauna therapy for congestive heart failure. After 2 weeks of sauna therapy, these showed improvements in 6-minute walking distance, reduced heart size on chest X-ray and reduced severity of disease compared to no significant improvements in a control group receiving standard medical care.
So should you have a sauna if you have high blood pressure?
If you have untreated hypertension, you should avoid saunas until your blood pressure is well controlled. People with uncontrolled hypertension are at risk of increased blood pressure during or after a sauna.
Even if you have well-controlled high blood pressure, consult your doctor before having a sauna.
Drink several glasses of water before and after a sauna to prevent dehydration.
Measure your blood pressure before and after a sauna (every 15 minutes until readings are stabilised) to see how you respond as an individual – everyone is different.
Don’t have a sauna alone, or when you are ill or have been drinking alcohol.
If your blood pressure is raised, self-monitoring is key to maintaining good control.
Click here for advice on choosing a blood pressure monitor to use at home.
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