Heat therapy: Could sauna use protect the health of our hearts?

Does Finish sauna bathing have vascular health benefits?

Finnish sauna use is growing in popularity globally due to the associated links with physical health benefits, such as improved heart health. However, the physiological mechanisms underlying this association remain unknown. Society member Dr Amélie Debray, a postdoctoral researcher working at the Cardiovascular Health and Autonomic Regulation Laboratory at McGill University (Canada), has been looking into this. She tells us more about the randomised controlled trial she carried out at the Montreal Heart Institute (Canada) with her principal investigator Dr Daniel Gagnon to investigate the relationship between sauna use and its cardioprotective potential.

Studying physiological responses to exercise and the heat

Growing up active and involved in sports sparked my curiosity about how the body responds to exercise and heat stress. I have always been especially fascinated by how females adapt from a cardiovascular perspective. This interest has been shaped and strengthened throughout my master’s, PhD, and now postdoctoral positions, where I have had the chance of working with exceptional and passionate mentors who truly shaped my curiosity and pushed me to explore this field in depth.

What fascinates me most is just how adaptable the human body is. Whether we are exercising, facing heat, or dealing with other physiological stressors, the body has these amazing, integrated ways of protecting itself and maintaining balance. I’m particularly drawn to studying these responses in females, since so much of cardiovascular and environmental physiology has historically focused on males.

I love exploring how things like hormones, sex-specific physiology, and environmental conditions all interact to shape cardiovascular and thermoregulatory responses. For me, every new insight feels exciting, not just because it advances our understanding, but because it can make a real difference in people’s health, helping guide safer exercise practices and inform public health.

Heat-based interventions to reduce the risk of heart disease

This led to an investigation of the impact of passive heat exposure on vascular function and heart health, which I presented at the meeting ‘Thermal Physiology in Health and Disease: Mechanisms and Therapeutic Applications Effect’. The research stems from the growing recognition that regular heat exposure, such as Finnish sauna bathing, may support cardiovascular health. Observational studies consistently show that frequent sauna use is associated with a substantially lower risk of heart disease and mortality, as well as reductions in high blood pressure, stroke, and neurocognitive disorders.

Notably, these benefits appear to extend even to individuals with risk factors, such as type 2 diabetes. While these findings suggest a potential protective effect of heat on the heart, we cannot yet conclude that sauna use directly causes these benefits. The leading hypothesis is that repeated heat exposure may improve vascular function, but well-controlled clinical trials are still needed to confirm this.

Finnish sauna bathing and vascular health

We wanted to see whether an eight-week Finnish sauna program could improve both large and small vessel health, reduce arterial stiffness, and lower blood pressure in adults with coronary artery disease, a group that really needs effective and accessible lifestyle interventions. On top of that, we were curious from a thermoregulation perspective whether repeated sauna use could help these participants adapt to heat, essentially inducing heat acclimation.

Assessing cardiovascular outcomes

In our study, we recruited 41 adults, around 62 years old on average, with stable coronary artery disease (33 males and 8 females). They were randomly assigned to either an eight-week Finnish sauna intervention or a control group that maintained their usual lifestyle. For the sauna group, participants completed four sessions per week, each lasting 20 to 30 minutes, at about 80°C with 13% relative humidity.

We assessed several cardiovascular outcomes both before and after the intervention. These included brachial artery flow-mediated dilation to measure endothelial function, carotid-femoral pulse wave velocity for central arterial stiffness, total and peak post-occlusion forearm reactive hyperemia to evaluate microvascular function, and blood pressure using automated auscultation.

Heat acclimation

After the eight-week sauna intervention, we saw that participants had a lower resting core temperature and an increased sweat rate during sauna exposure, which suggests they were starting to acclimate to the heat. However, when we looked at vascular health, the results were more mixed.

Brachial artery flow-mediated dilation did not change between the sauna and control groups. Microvascular function, actually showed a small decrease in the sauna group and a slight increase in the control group. Central arterial stiffness, as well as systolic and diastolic blood pressure, did not differ between groups either.

Overall, these findings suggest that in adults with stable coronary artery disease, doing four sauna sessions a week for eight weeks didn’t really improve measures of vascular health. That said, participants did show signs of heat acclimation.

Sauna use and heat adaptation

The main takeaway of our study is that while sauna use may help with heat adaptation, it doesn’t seem to meaningfully improve marker of vascular health in our population of adults with stable coronary artery disease over an eight-week period. This tells us that either longer interventions, higher “doses” of heat exposure, or combining sauna with other lifestyle strategies might be needed to see cardiovascular benefits. Moving forward, we want to explore these possibilities to better understand who might benefit most from heat-based interventions.