Finnish Sauna Bathing and Vascular Function in Adults with Coronary Artery Disease: Preliminary Analysis of a Randomized Controlled Trial

Abstract

Background Regular Finnish sauna use is associated with a reduced risk of cardiovascular mortality. However, mechanisms underlying this relationship remain unknown. Other forms of heat therapy have been shown to improve markers of vascular function in healthy young adults as well as in middle-aged adults with cardiovascular risk factors and older adults with chronic heart failure. Nevertheless, no experimental study has addressed the effects of regular Finnish sauna use on vascular function. This study tested the hypothesis that an 8-week Finnish sauna intervention improves vascular function in adults with stable coronary artery disease (CAD) Methods Fourteen middle-aged to older adults (61 ± 7 years, 12 men/2 women) with stable CAD and naïve to heat therapy were randomized to 8 weeks of Finnish sauna (4 sessions/week, 20-30 min/session) (SAUNA, n=7) or maintenance of habitual lifestyle (CTRL, n=7). Before and after the intervention, resting blood pressure, brachial artery flow-mediated dilation (FMD) and cutaneous vasodilation during local heating at 39°C were measured. Brachial artery FMD was used as an index of conduit artery endothelial function, peak and area under the curve (AUC) of forearm vascular conductance (FVC) during reactive hyperemia were used as indices of peripheral microvascular reactivity and the plateau of cutaneous vascular conductance, expressed as percentage of maximal (%CVC) during local heating, was used as an index of skin microvascular reactivity. Results Resting systolic (P for interaction = 0.55) and diastolic blood pressure (P for interaction = 0.56) were not different between interventions. Contrary to our hypothesis, no effect of the sauna intervention was observed on FMD (SAUNA pre to post: 4.2 ± 2.4 to 4.5 ± 2.1%, CTRL pre to post: 5.0 ± 1.8 to 4.3 ± 2.1%, P for interaction = 0.37). Peripheral microvascular reactivity decreased following the SAUNA intervention and increased following CTRL, according to peak FVC (SAUNA pre to post: 2.7 ± 1.2 to 2.3. ± 1.2 ml/min/mmHg, CTRL pre to post: 3.2 ± 0.6 to 3.9 ± 0.7 ml/min/mmHg, P for interaction = 0.03) and FVC-AUC (SAUNA pre to post: 1.4 ± 0.6 to 1.1 ± 0.6 ml/mmHg, CTRL pre to post: 1.7 ± 0.5 to 2.1 ± 0.5 ml/mmHg, P for interaction = 0.03). However, within group changes in both peak FVC and FVC-AUC were not significant (all P > 0.06). No effect of either intervention was observed on %CVC (P for interaction = 0.33). Conclusion These results suggest that 4 sessions of Finnish sauna bathing per week for 8 weeks does not improve markers of macro- or microvascular function in middle-aged to older adults with stable CAD.