Is it time to start recommending regular sauna bathing to improve heart health?
Mounting evidence shows that hitting the heated chambers can produce some of the same cardiovascular benefits as aerobic exercise. While a post-workout sauna can compound the benefits of exercise, the hormetic effects of heat therapy alone can produce significant gains for microvascular and endothelial function, no workout required.
Dr Matthew Ganio
“There’s enough evidence to say that regular sauna use improves cardiovascular health,” Matthew S. Ganio, PhD, a professor of exercise science at the University of Arkansas in Fayetteville, who studies thermoregulatory responses and cardiovascular health, said.
“The more they used it, the greater the reduction in cardiovascular events like heart attack. But you don’t need to be in there more than 20 to 30 minutes. That’s where it seemed to have the best effect,” Ganio said, adding that studies have shown a dose-response.
A prospective cohort study published in 2015 in JAMA Internal Medicine included 20 years of data on more than 2300 Finnish men who regularly sauna bathed. The researchers found that among participants who sat in saunas more frequently, rates of death from heart disease and stroke were lower than among those who did so less often.
The body experiences several physiologic changes when exposed to heat therapy of any kind, including sauna, hot water submerging, shortwave diathermy, and heat wrapping. Many of these changes involve elements of the cardiovascular system, said Earric Lee, PhD, an exercise physiologist and postdoctoral researcher at the University of Jyväskylä in Finland, who has studied the effects of sauna on cardiovascular health.
Dr Earric Lee
The mechanisms by which heat therapy improves cardiovascular fitness have not been determined, as few studies of sauna bathing have been conducted to this degree. One driver appears to be cutaneous vasodilation. To cool the body when exposed to extreme external heat, cutaneous vessels dilate and push blood to the skin, which lowers body temperature, increases heart rate, and delivers oxygen to muscles in the limbs in a way similar to aerobic exercise.
Sauna bathing has similar effects on heart rate and cardiac output. Studies have shown it can improve the circulation of blood through the body, as well as vascular endothelial function, which is closely tied to vascular tone.
“Increased cardiac output is one of the physiologic reasons sauna is good for heart health,” Ganio said.
During a sauna session, cardiac output can increase by as much as 70% in relation to elevated heart rate. And while heart rate and cardiac output rise, stroke volume remains stable. As stroke volume increases, the effort that muscle must exert increases. When heart rate rises, stroke volume often falls, which subjects the heart to less of a workout and reduces the amount of oxygen and blood circulating throughout the body.
Dr Christopher Minson
Heat therapy also temporarily increases blood pressure, but in a way similar to exercise, which supports better long-term heart health, said Christopher Minson, PhD, the Kenneth M. and Kenda H. Singer Endowed Professor of Human Physiology at the University of Oregon, in Eugene.
A small study of 19 healthy adults that was published in Complementary Therapies in Medicine in 2019 found that blood pressure and heart rate rose during a 25-minute sauna session as they might during moderate exercise, equivalent to an exercise load of about 60–100 watts. These parameters then steadily decreased for 30 minutes after the sauna. An earlier study found that in the long term, blood pressure was lower after a sauna than before a sauna.
Upregulated Heat Shock Proteins
Both aerobic exercise and heat stress from sauna bathing increase the activity of heat shock proteins. A 2021 review published in Experimental Gerontology found that heat shock proteins become elevated in cells within 30 minutes of exposure to heat and remain elevated over time — an effect similar to exercise.
Dr Hunter Waldman
“Saunas increase heat shock proteins that break down old, dysfunctional proteins and then protect new proteins from becoming dysfunctional,” Hunter S. Waldman, PhD, an assistant professor of exercise science at the University of North Alabama, in Florence, said. This effect is one way sauna bathing may quell systemic inflammation, Waldman said.
According to a 2018 review published in BioMed Research International, an abundance of heat shock proteins may increase exercise tolerance. The researchers concluded that the positive stress associated with elevated body temperature could help people be physically active for longer periods.
Added stress, especially heat-related strain, is not good for everyone, however. Waldman cautioned that heat exposure, be it through a sauna, hot tub, or other source, can be harmful for pregnant women and children and can be dangerous for people who have low blood pressure, since blood pressure often drops to rates that are lower than before taking a sauna. It also can impair semen quality for months after exposure, so people who are trying to conceive should avoid sauna bathing.
Anyone who has been diagnosed with a heart condition, including cardiac arrhythmia, coronary artery disease, and congestive heart failure, should always consult their physician prior to using sauna for the first time or before using it habitually, Lee said.
Effects Compounded by Exercise
Minson stressed that any type of heat therapy should be part of a lifestyle that includes mostly healthy habits overall, especially a regular exercise regime when possible.
“You have to have everything else working as well: finding time to relax, not being overly stressed, staying hydrated ― all those things are critical with any exercise training and heat therapy program,” he said.
Lee said it’s easy to overhype the benefits of sauna bathing and agreed the practice should be used in tandem with other therapies, not as a replacement. So far, stacking research has shown it to be an effective extension of aerobic exercise.
A June 2023 review published in Mayo Clinic Proceedings found that while sauna bathing can produce benefits on its own, a post-workout sauna can extend the benefits of exercise. As a result, the researchers concluded, saunas likely provide the most benefit when combined with aerobic and strength training.
While some of the benefits of exercise overlap those associated with sauna bathing, “you’re going to get some benefits with exercise that you’re never going to get with sauna,” Ganio said.
For instance, strength training or aerobic exercise usually results in muscle contractions, which sauna bathing does not produce.
If a person is impaired in a way that makes exercise difficult, taking a sauna after aerobic activity can extend the cardiovascular benefits of the workout, even if muscle-building does not occur, Lee said.
“All other things considered, especially with aerobic exercise, it is very comparable, so we can look at adding sauna bathing post exercise as a way to lengthen the aerobic exercise workout,” he said. “It’s not to the same degree, but you can get many of the ranging benefits of exercising simply by going into the sauna.”
The authors have disclosed no relevant financial relationships.
Kaitlin Sullivan is a freelance health and science journalist based in Colorado.
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