Passive Heat Therapy Lowers Systolic Blood Pressure and Improves Vascular Endothelial Function in Healthy Older Adults
Authors: Brunt Vienna E , Rosenberg Hannah L , Bazzoni Amy E , Nguyen Kathy H , Frye Jacob , Chonchol Michel , Minson Christopher T , Seals Douglas R 
Published: June 2021

Aging is associated with elevated systolic blood pressure (SBP) and impaired vascular function, characterized by endothelial dysfunction and stiffening of the large elastic arteries, which all increase risk for cardiovascular diseases (CVD). Passive repeated heat exposure (“heat therapy”) is associated with lower CVD risk at the population level and improves CV function in animals, healthy young adults, and selective groups of patients with clinical disease. It is unknown, however, if heat therapy lowers SBP and/or improves vascular function in late middle‐aged to older (MA/O) adults free of clinical diseases/disorders.PurposeTo determine if heat therapy via hot water immersion in healthy MA/O adults lowers SBP and/or improves markers of vascular health that are independent risk factors for CVD.MethodsTen healthy MA/O men and post‐menopausal women (57–76 years) were randomly assigned to participate in thirty 60‐min sessions of either hot (40.5°C; N=6, 3M/3F, 67±3 years) or thermoneutral (36°C, “sham”; N=4, 1M/3F, 69±2 years) water immersion. Resting (casual) BP and ultrasound‐ and tonometry‐based measures of vascular function and structure were measured at baseline and 24–72 h after the last water immersion session. Data are mean±S.E. Changes in outcome variables were compared within groups by paired t‐test.ResultsHot water immersion increased rectal temperature (Tre) from 36.9±0.2 to 38.7±0.1°C (p<0.001; data from first session), whereas no changes in Tre were observed in sham subjects (resting: 37.2±0.1 vs. peak: 37.3±0.1°C, p=0.23). Adherence was good, with subjects completing all sessions in 9.8±0.4 weeks (3.1±0.1 sessions/week). Heat therapy was well‐tolerated, with only 3% of sessions ending early due to occurrence of mild heat‐related symptoms (e.g., lightheadedness). Heat therapy decreased SBP by 10 mmHg on average (130±4 vs. 120±5 mmHg, p=0.04), increased endothelial function by ~50% (brachial artery flow‐mediated dilation, FMDBA: 4.4±0.7 vs. 6.5±0.9%, p<0.01), and decreased carotid intima media thickness (cIMT) by ~10% (0.70±0.02 vs. 0.64±0.03 mm, p=0.02), but did not significantly alter arterial stiffness (carotid‐femoral pulse wave velocity, PWV: 8.6±0.4 vs. 8.2±0.7 m/s, p=0.48), or diastolic BP (DBP: 81±4 vs. 78±5 mmHg, p=0.36). No effects were observed in sham subjects (SBP: 133±11 vs. 131±12 mmHg, p=0.31; FMDBA: 4.9±0.9 vs. 4.8±0.7%, p=0.92; cIMT: 0.69±0.02 vs. 0.68±0.03 mm, p=0.77; PWV: 9.6±1.6 vs. 9.3±1.6 m/s, p=0.35; DBP: 79±3 vs. 74±2 mmHg, p=0.17).ConclusionOur preliminary results suggest that in healthy MA/O adults, heat therapy is safe, is associated with excellent adherence, and induces clinically‐significant reductions in casual SBP and improvements in endothelial function comparable to or greater than those typically observed with aerobic exercise training. Heat therapy also induces a unique reduction in cIMT typically found only with longer‐term pharmacological therapies. Heat therapy may be a promising lifestyle‐based strategy for reducing SBP, endothelial dysfunction and, possibly, CVD risk with aging.Support or Funding InformationNCT03264508This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.