Passive heat therapy improves endothelial function, arterial stiffness and blood pressure in sedentary humans

Abstract

Key pointsr A recent 30 year prospective study showed that lifelong sauna use reduces cardiovascular-related and all-cause mortality; however, the specific cardiovascular adaptations that cause this chronic protection are currently unknown.r We investigated the effects of 8 weeks of repeated hot water immersion ('heat therapy') on various biomarkers of cardiovascular health in young, sedentary humans.r We showed that, relative to a sham group which participated in thermoneutral water immersion, heat therapy increased flow-mediated dilatation, reduced arterial stiffness, reduced mean arterial and diastolic blood pressure, and reduced carotid intima media thickness, with changes all on par or greater than what is typically observed in sedentary subjects with exercise training.r Our results show for the first time that heat therapy has widespread and robust effects on vascular function, and as such, could be a viable treatment option for improving cardiovascular health in a variety of patient populations, particularly those with limited exercise tolerance and/or capabilities. AbstractThe majority of cardiovascular diseases are characterized by disorders of the arteries, predominantly caused by endothelial dysfunction and arterial stiffening. Intermittent hot water immersion ('heat therapy') results in elevations in core temperature and changes in cardiovascular haemodynamics, such as cardiac output and vascular shear stress, that are similar to exercise, and thus may provide an alternative means of improving health which could be utilized by patients with low exercise tolerance and/or capabilities. We sought to comprehensively assess the effects of 8 weeks of heat therapy on biomarkers of vascular function in young, sedentary subjects. Twenty young, sedentary subjects were assigned to participate in 8 weeks (4-5 times per week) of heat therapy (n = 10; immersion in a 40.5°C bath sufficient to maintain rectal temperature ࣙ 38.5°C for 60 min per session) or thermoneutral water immersion (n = 10; sham). Eight weeks of heat therapy increased flow-mediated dilatation from 5.6 ± 0.3 to 10.9 ± 1.0% (P < 0.01) and superficial femoral dynamic arterial compliance from 0.06 ± 0.01 to 0.09 ±0.01 mm 2 mmHg −1(P = 0.03), and reduced (i.e. improved) aortic pulse wave velocity from 7.1 ± 0.3 to 6.1 ± 0.3 m s −1(P = 0.03), carotid intima media thickness from 0.43 ± 0.01 to 0.37 ± 0.01 mm (P < 0.001), and mean arterial blood pressure from 83 ± 1 to 78 ± 2 mmHg (P = 0.02). No changes were observed in the sham group or for carotid arterial compliance, superficial femoral intima media thickness or endothelium-independent dilatation. Heat therapy improved endothelium-dependent dilatation, arterial stiffness, intima media thickness and blood pressure, indicating improved cardiovascular health. These data suggest heat therapy may provide a simple and effective tool for improving cardiovascular health in various populations.

Passive heat stress reduces circulating endothelial and platelet microparticles

“…These surprising findings potentially represent novel favourable effects that buttress the vascular benefits previously reported with non-pathophysiological hyperthermia (Umscheif et al 2010;Ohori et al 2012;Laukkanen et al 2015;Brunt et al 2016;Romero et al 2017). To our knowledge, this is the first study to determine the effects of passive heat stress on circulating microparticles.…”

“…To our knowledge, this is the first study to determine the effects of passive heat stress on circulating microparticles. In addition, Brunt et al (2016) recently reported that 8 weeks of passive whole-body heat therapy (hot water immersion until a rectal temperature of 38.5°C, four or five times per week) reduced resting systolic and diastolic blood pressure, arterial stiffness and carotid intima-media thickness and improved flow-mediated dilatation of the brachial artery in young adults. The notion of therapeutic benefits from controlled hyperthermia is not new (Lee Titsworth et al 2014) but has recently gained interest in large part after a 30 year prospective study (Laukkanen et al 2015) indicating that lifetime sauna use is associated with lower rates of cardiovascular system-related deaths.…”

Sauna Bathing and Incident Hypertension: A Prospective Cohort Study

“…12 Heat therapy such as hot water immersion is associated with several health benefits including lower levels of resting blood pressure potentially reducing the risk of cardiovascular diseases CVD. 13 However, in this study, sauna bathing A typical Finnish sauna session is indeed characterized by warming up in the sauna with subsequent cooling and relaxation; this can positively modulate the autonomic system and may further explain the effects on blood pressure reduction. 18,19 Thirdly, heart rate may increase up to 100-150 beats per minute during sauna bathing session 4,20-23 which increases vasodilatation and improves function of the vasculature; these are the same benefits that are associated with low and moderate intensity physical exercise training.…”

The effect of passive heating on heat shock protein 70 and interleukin-6: A possible treatment tool for metabolic diseases?

“…57 Although this relationship does not establish causality, 31,58 it is nonetheless an interesting link that is supported by recent investigations. 59-61 PH appears to improve vascular function, with improvements to flow-mediated dilatation, arterial stiffness and blood pressure reported after 8 weeks of PH. 59 Moreover, Thomas et al have shown that 30 minutes of PH can induce a significant shear stress response and a reduction in mean arterial pressure in patients with peripheral arterial disease.…”

“…59-61 PH appears to improve vascular function, with improvements to flow-mediated dilatation, arterial stiffness and blood pressure reported after 8 weeks of PH. 59 Moreover, Thomas et al have shown that 30 minutes of PH can induce a significant shear stress response and a reduction in mean arterial pressure in patients with peripheral arterial disease. 62 Furthermore, in a healthy cohort who underwent matched duration PH or EX, the PH group demonstrated a greater shear stress response compared to that in response to EX.…”