Finnish Sauna Bathing and Vascular Health of Adults with Coronary Artery Disease: a Randomized Controlled Trial

Aims: Regular Finnish sauna use is associated with a reduced risk of cardiovascular mortality. However, physiological mechanisms underlying this association remain unknown. This study determined if an 8-week Finnish sauna intervention improves peripheral endothelial function, microvascular function, central arterial stiffness, and blood pressure in adults with coronary artery disease (CAD). Methods: Forty-one adults (62 ± 6 years, 33 men/8 women) with stable CAD were randomised to 8 weeks of Finnish sauna use (n=21, 4 sessions/week, 20-30 min/session, 79°C, 13% relative humidity) or a control intervention (n=20, lifestyle maintenance). Brachial artery flow-mediated dilation (FMD), carotid-femoral pulse wave velocity (cf-PWV), total (area under the curve) and peak post-occlusion forearm reactive hyperemia, and blood pressure (automated auscultation) were measured before and after the intervention. Results: After the sauna intervention, resting core temperature was lower (-0.27°C [-0.54, -0.01], p=0.046) and sweat rate during sauna exposure was greater (0.3 L/h [0.1, 0.5], p=0.003). The change in brachial artery FMD did not differ between interventions (control: 0.07% [-0.99, +1.14] vs. sauna: 0.15% [-0.89, +1.19], interaction p=0.909). The change in total (p=0.031) and peak (p=0.024) reactive hyperemia differed between interventions due to a non-significant decrease in response to the sauna intervention and an increase in response to control. The change in cf-PWV (p=0.654), systolic (p=0.951) and diastolic (p=0.292) blood pressure did not differ between interventions. Conclusion: These results demonstrate that 4 sessions of Finnish sauna bathing per week for 8 weeks does not improve markers of vascular health in adults with stable CAD.