Study Suggests a Hot Bath Could Help Reduce Blood Pressure

Key Takeaways

• A 30-minute hot bath lowered blood pressure more than a 30-minute bike workout in a small study.
• Hot baths should not replace exercise, but they may help people who cannot exercise regularly.
• Ask your healthcare provider before trying hot-water therapy if you have certain health conditions or take medicines that affect heat response.

Many people turn to a hot bath to relax after a long day. New research suggests that this simple habit may also have a blood pressure benefit: 30 minutes in hot water lowered blood pressure more than a 30-minute workout. Experts say that does not mean people should trade exercise for bathing, but hot-water immersion could still be helpful for those who are unable to exercise regularly.

What the Study Found

A recent study published in the European Journal of Applied Physiology compared the effects of a hot bath at about 40 degrees Celsius, or 104 degrees Fahrenheit, with a 30-minute stationary bike session to see which lowered blood pressure more. The researchers studied 25 adults ages 45 to 70 who were either overweight or had obesity.

The participants took part in just one session of each activity, and the early results suggested that hot-water immersion increased blood flow and reduced blood pressure more than cycling.

“The main takeaway from our studies is that a single 30-minute session of hot-water immersion can produce substantial responses across the cardiovascular system,” said Kristanti Wigati, MSi, PhD, lead researcher and professor in the Department of Medical Physiology and Biochemistry at Universitas Airlangga in Indonesia.

“This is important because increases in blood flow and the resulting shear stress provide a stimulus to the blood vessel wall that may contribute to vascular adaptation over time,” Wigati said.

In other words, the higher blood flow caused by hot baths may help blood vessels relax and stay healthy over time. Because this was only a short-term study, more research is needed to understand whether the effect leads to lasting blood pressure benefits.

Wigati also stressed that promising results do not mean hot baths should replace physical activity. Still, she said they may offer a useful option for people who have trouble exercising.

“Exercise provides many health benefits that passive heating cannot reproduce,” she said. “Hot-water immersion may have potential as a complementary approach, particularly for people who find it difficult to exercise regularly, and further research is needed to understand how these acute cardiovascular responses translate into longer-term health benefits.”

How Hot-Water Immersion Affects Blood Pressure

The early findings suggest hot-water immersion may help lower blood pressure, but how does it work?

“Heat directly applied to the skin will cause skin blood vessels to open up, or dilate,” said Christopher Minson, PhD, professor of human physiology at the University of Oregon. “This will cause the heart rate to increase for the cardiovascular system to maintain blood pressure.”

As blood vessels widen, blood can move through them more easily. That can reduce the pressure against the vessel walls and lead to a drop in blood pressure.

But the effects depend on how long and how often you do it. “After a single session, blood pressure will be reduced for a few hours,” Minson said. “With repeated use, most studies have shown that it will remain lower over time.”

This study looked only at one session of hot-water immersion, so more research is needed to understand the long-term effects of heat therapy on blood pressure. Even so, hot baths and hot tubs are not the only ways to potentially experience the temporary blood pressure effects of heat therapy.

“The most robust evidence of the benefits of heat therapy comes from studies using traditional sauna,” Minson added. “There is some evidence of benefits from other types of heat exposure, but overall these responses are less robust than hot-water immersion or traditional sauna.”

Water-based heat therapy, such as hot baths, and air-based heat therapy, such as saunas, also affect the body differently. More research is needed before scientists can fully understand the specific benefits of each type, how long each must be used before results appear, and which is better for blood pressure.

“Our studies specifically examined lower-body hot-water immersion at 40 degrees Celsius [104 degrees Fahrenheit], so we can’t assume that a particular dry or infrared sauna protocol would produce the same responses,” Wigati said. “The broader evidence does suggest that different forms of passive heat therapy can provide a cardiovascular stimulus, but they shouldn’t necessarily be considered interchangeable.”

Should You Try It?

Hot-water immersion may offer temporary blood pressure benefits, but it is not safe for everyone.

“Hot-water immersion was well tolerated by the older adults with overweight and obesity in our studies, but we should be cautious about assuming that the same protocol is suitable for everyone,” Wigati said. “Immersion in hot water raises body temperature and heart rate, dilates the blood vessels, redistributes blood toward the skin, and can lower blood pressure, so for some people this may cause dizziness or light-headedness.”

According to Wigati, you should also check with a healthcare provider before trying hot-water immersion if you have a heart condition, have problems with heat tolerance, take medications that affect your response to heat, are pregnant, or have a skin condition that makes you sensitive to hot water.

If you are not sure about hot-water immersion therapy and want other ways to lower blood pressure, several options are available. “These include regular exercise, maintaining a healthy body weight, eating a balanced diet rich in fruits, vegetables, and whole foods, limiting alcohol intake, getting adequate sleep, managing stress, and stopping smoking if you smoke,” Wigati said.

Still, the best way to lower blood pressure is to follow your healthcare provider’s advice, since recommendations can be tailored to your needs. “People with hypertension should continue any prescribed treatment and discuss these strategies with their healthcare provider,” Wigati emphasized. “Passive heat therapy should be considered a potential addition to established approaches, rather than a substitute for them.”