Background: Passive heat stress shows promise as an effective strategy to reduce the risk of cardiovascular diseases (CVD) as an alternative or adjunct to exercise and/or medication. Improving function of the endothelium is one of the key targets underlying the reduction in CVD risk.
Aims: We hypothesised that endothelial-dependent dilation, an index of endothelial cell function and nitric oxide bioavailability, is greater in healthy, older adults who regularly partake in sauna bathing compared to those who do not. To test whether sauna provides greater benefits to those with worse baseline vascular impairments, we additionally hypothesised that the improvement to endothelial-dependent dilation in regular sauna users compared to non-users is augmented in a group of older adults with coronary artery disease (CAD).
Methods: Adults aged 50-80 years (n=16) were recruited from the community and all healthy participants were free from CVD as well as medications related to the primary or secondary prevention of CVD. A subset of participants with stable coronary artery disease (CAD) was also recruited (n=8). Informed consent was obtained prior to data collection (Montreal Heart Institute Research Ethics Committee #2017-2179). Endothelial function was measured via the technique of flow-mediated dilation (FMD) using duplex Doppler ultrasound imaging of the brachial artery. The results were compared between groups using a one-way ANOVA performed in SPSS and the critical P value was set at 0.05. When significance was identified, post-hoc tests were performed with a Bonferroni correction.
Results: Baseline brachial artery diameter (P=0.235) and conductance (P=0.812) were not different between groups, but reactive hyperemia SRAUC was lower in CAD patients compared to healthy older adults (P=0.013). However, neither variable significantly influenced FMD when included in the model as a covariate. Additionally, there were no differences between groups for FMD (healthy users: 3.9 [1.6]%, non-users: 4.3 [1.8]% vs. CAD users: 3.1 [2.0]%, CAD non-users: 2.6 [1.8]%; P=0.224) or peak vascular conductance during reactive hyperemia (healthy users: 4.5 [2.2] ml/min/mmHg, non-users: 4.2 [2.2] ml/min/mmHg vs. CAD users: 4.0 [2.2] ml/min/mmHg, CAD non-users: 4.5 [1.0] ml/min/mmHg; P=0.723).
Conclusion: The results of this pilot study indicate that endothelial-dependent dilation (measured via FMD) is not different between groups of habitual sauna users compared to non-users in older adults with and without CAD.