Can Finnish Sauna Bathing Induce Heat Acclimation in Adults with Stable Coronary Artery Disease?

Abstract

IntroductionExtreme heat is associated with a greater risk of mortality that particularly affects older adults with cardiovascular disease (CVD). Regular heat exposure induces an adaptation of thermoregulatory mechanisms (acclimation) that may alleviate thermal and/or cardiac strain during subsequent heat exposure. However, limited research has examined practical heat acclimation protocols that could be recommended to vulnerable populations, such as adults with CVD. The objective of this study was to test the hypothesis that 8 weeks of Finnish sauna bathing reduces core temperature and heart rate and increases sweating during heat exposure.Method14 participants (11 men/3 women, 63 ± 5 years, 28.7 ± 3.8 kg/m2) with stable coronary artery disease participated in an 8‐week Finnish sauna intervention (4 sessions/week, 20 to 30 min/session, at ~80°C, 20% humidity). Core temperature (ingestible telemetric pill), heart rate (Polar watch), and sweat rate (change in nude body weight) were measured during the first and last sauna sessions.ResultsResting core temperature prior to the first sauna session was 37.4 ± 0.4°C, compared to 37.1 ± 0.3°C prior to the last session (p= 0.04). Core temperature at the end of sauna bathing did not differ between the first (37.77 ±0.34°C) and the last (37.59 ± 0.31°C, p=0.20) sessions. Heart rate at the end of sauna bathing was greater during the last (90 ± 17 bpm) compared to first (85 ± 16 bpm, p=0.13) sessions. Sweat rate was greater during the last sauna session (first session: 8.6 ± 5.9 mL/min vs. last session: 5.1 ± 3.0 mL/min, p<0.01).ConclusionEight weeks of Finnish sauna bathing reduces resting core temperature and increases sweat rate during heat exposure in adults with stable coronary artery disease. However, these adaptations did not translate into reduced thermal and cardiac strain during heat exposure.