Heat Therapy for High Blood Pressure

Overseen By Brendan W Kaiser, PhD

Age: 18+

Sex: Any

Trial Phase: Academic

Sponsor: University of Colorado, Boulder

Must not be taking: Anticholinergics, Alpha-blockers, Beta-blockers, others

Disqualifiers: Obesity, Orthostatic hypotension, Atrial fibrillation, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: 38

Duration: 12 weeks

150 Participants Needed

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial explores how heat therapy, involving hot water immersion, might lower blood pressure and improve blood vessel health. Participants will undergo either hot water or neutral temperature water immersion about three times a week for 12 weeks. The study also examines how this therapy affects brain function and blood flow in individuals aged 40 and older. Those with high blood pressure, not taking more than two blood pressure medications, and able to safely handle heat exposure might be suitable candidates for this trial. As an unphased trial, it offers participants the chance to contribute to innovative research that could provide new insights into managing high blood pressure.

Will I have to stop taking my current medications?

The trial requires participants to refrain from using certain medications, such as dietary supplements, anti-inflammatory drugs, and some prescription medications, before and during water immersion visits. Specific medications like PDE5 inhibitors and nitrates have defined periods when they should not be taken around these sessions. It's best to discuss your current medications with the trial's medical team to see if adjustments are needed.

Is there any evidence suggesting that this trial's treatments are likely to be safe?

Research has shown that heat therapy, such as soaking in hot water, is generally safe. For individuals with certain conditions, like peripheral artery disease, heat therapy can help lower blood pressure and ease exercise. One study found that performing heat therapy at home for eight weeks lowered daytime blood pressure and improved blood vessel health.

While these studies suggest that heat therapy is usually well-tolerated, it does not improve all health measures. Regular sessions, such as three times a week for several weeks, are often necessary to see results. So far, no major reports of negative effects have emerged, indicating that most people tolerate it well. However, since individual responses vary, consulting a healthcare provider before joining a trial is always advisable. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Unlike typical treatments for high blood pressure, which often include medications like ACE inhibitors or beta-blockers, heat therapy offers a novel approach by using hot water immersion. This method is unique because it involves immersing the body in hot water about three times a week, which may help dilate blood vessels and improve circulation, potentially reducing blood pressure. Researchers are excited about this technique as it provides a non-pharmacological option that could be especially beneficial for individuals who prefer or require alternatives to medication.

What evidence suggests that heat therapy could be effective for high blood pressure?

Research has shown that heat therapy, a treatment in this trial, can improve heart health, including lowering blood pressure. One study found that soaking in hot water improved blood vessel function and reduced stiffness, both crucial for a healthy heart. Another study found that after 8-10 weeks of hot water immersion, young adults experienced better blood vessel function and lower blood pressure. This trial will compare heat therapy with thermoneutral water immersion, a sham comparator, to evaluate their effects on managing high blood pressure and improving heart health in older adults. ^{2 3 4 6 7}

Who Is on the Research Team?

Douglas R Seals, PhD

Principal Investigator

University of Colorado, Boulder

Vienna E Brunt, PhD

Principal Investigator

University of Colorado, Boulder

Are You a Good Fit for This Trial?

This trial is for adults aged 50 or older with systolic blood pressure between 120-159 mmHg. Participants must be mentally capable of consent, not pregnant, weight stable, and willing to maintain their lifestyle throughout the study. They should be healthy enough for heat exposure but can't join if they have unstable heart conditions, take multiple anti-hypertensive drugs (except one or two), do intense regular exercise, have recent major health changes including surgery or COVID-19.

Inclusion Criteria

I am willing to be randomly assigned to a treatment group.

Free from alcohol dependence or abuse, as defined by the American Psychiatry Association, Diagnostic and Statistical Manual of Mental Disorders (DSM-IV)

I am healthy enough for heat stress therapy, as confirmed by my doctors.

Exclusion Criteria

You have open wounds or skin conditions that could be affected by being in water for a long time, like in a pool.

I have atrial fibrillation or flutter.

I have not donated blood in the last 2 months.

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Treatment

Participants undergo hot water immersion or thermoneutral water immersion approximately 3 times per week for 12 weeks

12 weeks

Approximately 36 visits (in-person)

Follow-up

Participants are monitored for safety and effectiveness after treatment, with assessments at 4 and 12 weeks post-treatment

12 weeks

2 visits (in-person)

What Are the Treatments Tested in This Trial?

Interventions

• Heat therapy
• Thermoneutral water immersion

Trial Overview The study tests whether hot water immersion ('heat therapy') versus thermoneutral water immersion over approximately 12 weeks can lower blood pressure and improve vascular function in middle-aged and older adults.

How Is the Trial Designed?

Group I: Heat therapy Experimental Treatment 1 Intervention

Hot water immersion \~3x per week for 12 weeks

Group II: Thermoneutral water immersion Placebo Group 1 Intervention

Thermoneutral water immersion \~3x per week for 12 weeks

Who Is Running the Clinical Trial?

University of Colorado, Boulder

Lead Sponsor

Trials

128

Recruited

29,600+

Published Research Related to This Trial

Heat therapy, including methods like dry heat and water immersion, has shown beneficial effects in patients with heart failure, suggesting it could be a valuable complementary treatment alongside traditional medications and devices.

The authors propose using topically applied heat pads as a simple and cost-effective way to deliver heat therapy, encouraging further research into its potential as an adjunctive care option for heart failure patients.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Heat therapy in the management of heart failure. Weber, AA., Silver, MA.[2019]

In a study involving hypertensive patients treated with propranolol, both sauna baths and running exercises led to significant reductions in resting blood pressure and improvements in peripheral blood circulation over several weeks.

However, the therapeutic methods did not alter the hypertensive regulation during higher levels of physical exertion, indicating that while these treatments are beneficial at rest, they may not fully address blood pressure control during intense activity.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

[Effect of sauna and walking series on blood pressure, peripheral microcirculation and performance behavior in essential hypertension]. Winterfeld, HJ., Strangfeld, D., Siewert, H.[2008]

Sauna therapy positively influences blood pressure and peripheral hemodynamics in patients with hypertension and coronary heart disease, suggesting it can help manage hypertonic regulation issues.

Patients tolerated sauna therapy well, showing good compliance, although it did not improve the pumping function of the left ventricle after heart surgery.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

[Sauna therapy in coronary heart disease with hypertension after bypass operation, in heart aneurysm operation and in essential hypertension]. Winterfeld, HJ., Siewert, H., Strangfeld, D., et al.[2022]

In a study involving 19 patients (11 in the treatment group and 8 in the control group), combining thermal biofeedback training with progressive muscle relaxation significantly reduced systolic blood pressure by 20.6 mmHg and diastolic blood pressure by 14.4 mmHg over four weeks.

In contrast, the control group that only received progressive muscle relaxation showed a tendency for blood pressure to increase, highlighting the added benefit of thermal biofeedback in managing essential hypertension.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The effect of thermal biofeedback and progressive muscle relaxation training in reducing blood pressure of patients with essential hypertension. Hahn, YB., Ro, YJ., Song, HH., et al.[2019]

In a study of 129 patients with chronic heart failure, Waon therapy significantly reduced cardiac events, with only 31.3% of patients experiencing such events compared to 68.7% in the control group over a 5-year follow-up period.

The overall survival rate for patients receiving Waon therapy was 84.5%, suggesting that this non-pharmacological treatment may improve prognosis in chronic heart failure patients.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Waon therapy improves the prognosis of patients with chronic heart failure. Kihara, T., Miyata, M., Fukudome, T., et al.[2022]

Whole-body hot pack thermal therapy (HPTT) was found to produce a significant increase in skin vasodilation similar to that of Waon therapy (WT), suggesting it could be an effective alternative for chronic heart failure treatment.

In a study involving 19 healthy men, both therapies resulted in similar dilation of the brachial artery, indicating that HPTT can achieve comparable cardiovascular benefits without the need for specialized sauna equipment.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Cardiovascular reactions for whole-body thermal therapy with a hot pack and Waon therapy. Kominami, K., Noda, K., Takahashi, N., et al.[2020]

Heat therapy significantly reduces mean arterial, systolic, and diastolic blood pressure, as shown in a systematic review of 15 studies involving various healthy and clinical populations.

In addition to lowering blood pressure, heat therapy improves vascular function, indicated by enhanced flow-mediated dilatation, suggesting it could be a valuable tool for preventing and managing cardiovascular disease risk factors.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The effect of heat therapy on blood pressure and peripheral vascular function: A systematic review and meta-analysis. Pizzey, FK., Smith, EC., Ruediger, SL., et al.[2022]

Waon therapy, a repeated sauna treatment, significantly improved cardiac function in patients with chronic heart failure, as evidenced by an increase in left ventricular ejection fraction and exercise tolerance measured by the 6-minute walk test.

The therapy also enhanced endothelial function and reduced levels of neurohumoral factors like norepinephrine and brain natriuretic peptide, suggesting that improved endothelial function is a key mechanism behind the increased exercise capacity.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effect of repeated sauna treatment on exercise tolerance and endothelial function in patients with chronic heart failure. Ohori, T., Nozawa, T., Ihori, H., et al.[2022]

Waon therapy (WT) significantly reduced both systolic and diastolic blood pressure after a single session in patients with hypertension, indicating its immediate hypotensive effect.

Repeated WT sessions (more than 5 times) led to significant blood pressure reductions specifically in non-smoking patients, suggesting that WT could be an effective and simple method for managing hypertension in this group.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Blood pressure-lowering effect of repeated Waon therapy in non-smokers with hypertension. Kominami, K., Takahiza, E., Tabuchi, M., et al.[2021]

Citations

1. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC5023696/

Passive heat therapy improves endothelial function, arterial ... Heat therapy improved endothelium‐dependent dilatation, arterial stiffness, intima media thickness and blood pressure, indicating improved cardiovascular health ...

2. tandfonline.com tandfonline.com/doi/full/10.1080/23328940.2025.2465025

Both hot- and thermoneutral-water immersion reduce 24-h ... Recent research in Western medicine has reported that it improves cardiovascular health and is associated with a 50% reduction in the risk of stroke and ...

3. sciencedirect.com sciencedirect.com/science/article/pii/S2666667725001576

Non-acute effects of passive heating interventions on ... Current evidence from RCTs indicates that passive heating interventions may not improve most of the cardiometabolic or vascular health markers.

4. journals.physiology.org journals.physiology.org/doi/10.1152/ajpregu.00012.2025

Comparison of thermoregulatory, cardiovascular, and ... We have demonstrated that hot water immersion leads to the greatest thermoregulatory, cardiovascular, and immune responses compared with both ...

5. clinicaltrials.gov clinicaltrials.gov/study/NCT05300971

Study Details | NCT05300971 | Passive Heat Therapy for ... In addition, 8-10 weeks of hot water immersion in young adults has been shown to improve endothelial function and reduces arterial stiffness and blood pressure.

6. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC8285605/

Heat therapy: mechanistic underpinnings and applications to ... In patients with peripheral artery disease, heat therapy via hot water immersion lowered systolic blood pressure and improved exercise tolerance, as assessed ...

7. journals.physiology.org journals.physiology.org/doi/10.1152/japplphysiol.00977.2024

Home-based heat therapy lowers blood pressure and ... This study determined that 8 wk of home-based lower body heat therapy reduced ambulatory daytime systolic blood pressure and increased flow-mediated dilation.