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BACKGROUND: Regular Finnish sauna use has been associated with a reduced risk of cardiovascular mortality. However, physiological mechanisms underlying this association remain unknown. Other forms of heat therapy have been shown to improve markers of vascular health in healthy young adults, middle-aged adults with cardiovascular risk factors, and older adults with chronic heart failure. It is unknown if Finnish sauna use elicits similar adaptations. HYPOTHESIS: This study determined if Finnish sauna bathing improves markers of vascular health in adults with coronary artery disease (CAD). We tested the primary hypothesis that 8 weeks of Finish sauna bathing improves peripheral endothelial function. Secondary hypotheses were that Finish sauna bathing improves peripheral microvascular function, central arterial stiffness and blood pressure. METHODS: Forty-one adults (62 ± 6 years, 29.0 ± 4.3 kg/m2, 33 men/8 women) with stable CAD and naïve to heat therapy were randomized to 8 weeks of Finnish sauna use (n=21, 4 sessions/week, 20-30 min/session) or control intervention (lifestyle maintenance, n=20). Peripheral endothelial function (brachial artery flow-mediated dilation, FMD), central arterial stiffness (carotid-femoral pulse wave velocity), 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: Brachial artery FMD changed from 4.09 ± 2.05% to 4.24 ± 2.70% in response to sauna bathing and from 4.00 ± 2.02% to 4.10 ± 2.10% in response to the control intervention (p for interaction = 0.95). The change in central arterial stiffness (p for interaction = 0.82), total reactive hyperemia (p for interaction = 0.07), systolic (p for interaction = 0.95) and diastolic (p for interaction = 0.29) blood pressure also did not differ between interventions. The change in peak reactive hyperemia differed between interventions (p for interaction = 0.05) due to a slight decrease in response to sauna bathing (3.03 ± 1.42 to 2.75 ± 1.18 ml/min/mmHg, p=0.76) relative to a slight increase in response to control (2.78 ± 0.98 to 3.24 ± 1.00 ml/min/mmHg, p=0.05). CONCLUSION: These results demonstrate that 4 sessions of Finnish sauna bathing per week for 8 weeks does not improve markers of vascular health in older adults with stable CAD. Heart and Stroke Foundation of Canada, Fonds de Recherche du Québec – Santé This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.