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AgingNCT05300971

Passive Heat Therapy for Lowering Systolic Blood Pressure and Improving Vascular Function in Mid-life and Older Adults

A study testing Heat therapy and Thermoneutral water immersion in people with Aging, run by University of Colorado, Boulder at 1 site in United States.

Recruiting

Looking for participants now. Contact the study team or a site below to ask about taking part.

Sites and contacts
Official record
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Trial summary

This study aims to determine the effects of ~12 weeks of repeated hot water immersion ("heat therapy") vs. thermoneutral water immersion on blood pressure and vascular function in late middle-life to older (≥40 years) adults. Read more about this study

Who is it for?
Ages 40 years and olderHealthy volunteers can take part
Conditions the study is for
Aging
What is being tested?
Heat therapy and Thermoneutral water immersion
Could I receive a placebo?
Yes, some participants may receive a placebo
How many people
120 participants
Where
1 siteUnited States
Study dates
1 Aug 2022to 1 Feb 2028
Phase
Interventional
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 40 years and older
  • All sexes
  • Healthy volunteers accepted
  • Adult, Older adult

Who may be able to join

  • Able to provide informed consent (no clinical diagnosis of dementia or related diseases AND mini mental state exam score >20).
  • Willing to accept random assignment to intervention.
  • Aged 40+ years.
  • Premenopausal women must not be pregnant (confirmed by urine pregnancy test).
  • Casual systolic blood pressure 115-159 mmHg.
  • Sufficiently healthy to undergo heat stress, as determined by the CTRC physician Dr. Wolfe and physician of record Dr. Chonchol based on medical history, physical exam, blood chemistries, and 12-lead ECG at rest and during the graded exercise test. Subjects with established clinical diseases may participate so long it is not determined that heat therapy could be detrimental to their health (determined case-by-case, but examples of subjects who may be excluded include those currently undergoing chemotherapy treatment or chronic kidney disease patients requiring dialysis).
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  • Ability to refrain from the use of dietary supplements, anti-inflammatory medications, and prescription medications prior to experimental testing and/or water immersion visits in some cases (occasionally used PDE5 inhibitors and nitrites) (for the durations described above), as determined by the CTRC physician and approved by the subject's primary care provider if deemed necessary (see Procedures below for more detail). (rationale: many of these agents can acutely modulate vascular function).
  • Weight stable in the prior 3 months (≤ 2 kg weight change) and willing to remain weight stable over the course of the study.
  • Willing to maintain physical activity, diet, and other lifestyle factors for the entire 6-month duration of the study.
  • Free from alcohol dependence or abuse, as defined by the American Psychiatry Association, Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

Who cannot join

  • Individuals taking 3+ anti-hypertensive medications (rationale: these individuals typically have resistant or secondary hypertension. Individuals taking 1-2 anti-hypertensive medications will still be included, with the exception of beta-blockers.)
  • SBP 140-159 mmHg but not on anti-hypertensive medications. (rationale: ACC/AHA guidelines indicate that immediate pharmacotherapy is advised for these individuals. Potential subjects with SBP in this range will discuss options/receive recommendations from a CTRC physician and be referred to their primary care provider. If they begin anti-hypertensive medication, they will be eligible to participate in the study after they have been on them for at least 3 months, assuming they still qualify. If they decide not to begin anti-hypertensive medications, they must receive approval for their primary care provider that it is ok for them to participate in the study.)
  • Regular vigorous aerobic/endurance exercise: >4 bouts per week for >30 min per bout at a workload of >10 METS, determined based on screening surveys and workload confirmed by MAQ during Visit 1. (rationale: aerobic exercise training independently lowers blood pressure and improves arterial function33,74,75).
  • Body mass index (BMI) >40 kg/m2 (rationale: BP and vascular measurements can be inaccurate in severely obese subjects and these subjects may differ in many ways from normal weight, overweight, or less obese subjects).
  • Current use of anticholinergics (e.g. amitriptyline), alpha-blockers (e.g. Flomax), and beta-blockers (e.g., propranolol) (rationale: these medications can interfere with thermoregulation and/or control of blood pressure during heat stress). *Note: anti-hypertensive medications besides beta-blockers will be allowed-see "Additional considerations for subjects taking anti-hypertensive medications" below under the intervention procedures for Section XI.).
  • Current use of certain prescription medications taken at a dose or frequency high enough to potentially interfere with thermoregulation and/or blood pressure control during heat stress. These include nitrates and nitrites (e.g. nitroglycerin), PDE5 inhibitors (e.g. Viagra), amphetamines (e.g., ADD/ADHD drugs), insulin, and thyroid medications. Risk of each of these classes of medications depends on dose and other medications also being taken. Thus, Drs. Wolfe and Chonchol will make decisions whether subjects taking these medications should be excluded. (Note: occasional use of PDE5 inhibitors and nitrates ok so long as they are not taken for the following durations around water immersion sessions, PDE5 inhibitors: 24 hours before through the 8 hours after; nitrates: 8 hours before through 8 hours after, and (for both classes of medications) in the 48 hours before through the 48 hours after visits in which nitroglycerin is administered [visits 3, 10, \& 13] - Drs. Wolfe and Chonchol can extend these durations as they deem necessary and will have the opportunity to do so during the medication review process at screening).
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  • Orthostatic hypotension, as determined by medical history or during screening as a reduction of >20 mmHg on SBP and/or >10 mmHg in diastolic BP within 3 min of going from seated to standing (rationale: passive heat therapy is contraindicated for individuals with orthostatic hypotension).
  • Active, untreated atrial fibrillation or flutter (rationale: it is possible individuals with atrial fibrillation/flutter may have a higher risk of arrhythmias during hot water immersion).
  • Unstable cardiovascular diseases (e.g., unstable angina or recent myocardial infarction or stroke) (rationale: heat therapy is contraindicated for individuals with unstable CVDs).
  • Recent major change in health status within previous 3 months (e.g., surgery, significant infection or illness, including COVID-19). What is considered "major" or "significant" may be evaluated by the physician of record on a case-by-case basis. An example of a surgery that would likely not be considered "major" is out-patient removal of a basal cell carcinoma. "Significant" infections include those requiring hospitalization or long durations (i.e., months) of recovery. Additionally, subjects with acute fever/illness (Tre ≥ 38.0°C) will not be able to undergo screening or participate in water immersion sessions until fever/illness has resolved. Subjects with a confirmed positive case of COVID-19 will not be able to participate until COVID-19 symptoms have resolved and 2 weeks after diagnosis. Subjects will be asked to let us know if they are sick so that sessions/testing can be rescheduled.
  • Open wounds or skin lesions. History of skin-related conditions or sensitivities to prolonged water immersion or exposure to pool chemicals.
  • Blood donation within the past 2 months (if subjects have donated blood within the last 2 months, we will ask if they are willing to delay the start of the study until it has been 2 months since their last blood donation)
  • Inability to tolerate blood draws, intravenous catheters, including past fainting in response to blood sampling. (rationale: at the least, we must be able to obtain enough blood for clinical chemistries to ensure safety).

Trial locations and contacts

1 site in 1 country. Contact the study team or a site near you to ask about taking part.

Vienna E Brunt, PhD contact

303-724-4898

vienna.brunt@cuanschutz.edu

Edwin Rodriguez, PhD contact

303-735-6410

Eddie.Rodriguez-1@colorado.edu

United States1 site, 1 recruiting
  • University of Colorado Boulder

    Boulder, Colorado, 80309

    Vienna E Brunt, PhD, 303-735-4554, vienna.brunt@colorado.edu

    Recruiting

Other trials in United States

About this study

This study aims to determine the effects of ~12 weeks of repeated hot water immersion ("heat therapy") vs. thermoneutral water immersion on blood pressure and vascular function in late middle-life to older (≥40 years) adults. The study also aims to determine the effects of ~12 weeks of heat therapy on fluid cognitive and cerebrovascular function.

Read the detailed description

Advancing age is the primary risk factor for cardiovascular diseases (CVD), which remain the leading cause of death in the developed world. The key process that links aging to increased risk of CVD is increases in systolic blood pressure and the development of arterial dysfunction (i.e., impaired endothelial function and arterial stiffening).

Passive heat therapy, in the form of repeated use of hot baths and saunas, has been used by several cultures for centuries; however, the physiological benefits are only now being elucidated. For example, recent studies have found that lifelong habitual sauna use is associated with considerably reduced risk of all-cause mortality, sudden cardiac death, CVD-related death. 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. Therefore, the investigators expect heat therapy to similarly improve blood pressure and vascular function in middle-life and older adults who are at greater risk of CVD.

Aging is also the primary risk factor for Alzheimer's disease and related dementias, as well as mild cognitive impairment (MCI). Above-normal systolic blood pressure (SBP; ≥115 mmHg) further increases risk of dementias, due, in part, to SBP-associated cerebrovascular dysfunction, i.e., impaired cerebral blood flow regulation. Accordingly, midlife and older adults with above-normal SBP are at the highest risk for cognitive decline driven by vascular contributions to cognitive impairment and dementias in this age group. Excessive reactive oxygen species-induced oxidative stress and reductions in nitric oxide (NO) bioavailability within the cerebral vasculature likely mediate cerebrovascular dysfunction with aging and contribute to MCI and Alzheimer's disease and related dementias in those with above-normal SBP.

Conditions
Aging
Being tested
Heat therapy, Thermoneutral water immersion
Keywords
Endothelial function, Arterial stiffness, Heat, Hot water immersion, Systolic blood pressure

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • Heat therapyOther

    36 sessions (~3x per week for 12 weeks) of hot water immersion in 40°C water, sufficient to raise body core temperature to 38.5°C, and 12 weeks of follow-up.

  • Thermoneutral water immersionOther

    36 sessions (~3x per week for 12 weeks) of thermoneutral water immersion in 36°C water to prevent changes in body core temperature >0.2°C, and 12 weeks of follow-up.

Study groups in NCT05300971
Study groupRoleWhat they receive
Heat therapyExperimentalHot water immersion ~3x per week for 12 weeks
Receives: Other: Heat therapy
Thermoneutral water immersionSham comparatorThermoneutral water immersion ~3x per week for 12 weeks
Receives: Other: Thermoneutral water immersion

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Change in casual systolic blood pressure from baseline to 2, 4, 6, 8, 10, and 12 weeks of heat therapy, and 4 and 12 weeks of follow-up.

    Casual brachial artery systolic blood pressure, measured in triplicate (and averaged)

    Measured: 0 weeks, 2 weeks, 4 weeks, 6 weeks, 8 weeks, 10 weeks, 12 weeks, 16 weeks, 24 weeks

Secondary outcomes (2)
  1. Change in 24-hour ambulatory systolic blood pressure from from baseline to 2, 4, 6, 8, 10, and 12 weeks of heat therapy, and 4 and 12 weeks of follow-up.

    Brachial artery systolic blood pressure measured over 24 hours with an ambulatory monitor

    Measured: 0 weeks, 2 weeks, 4 weeks, 6 weeks, 8 weeks, 10 weeks, 12 weeks, 16 weeks, 24 weeks

  2. Change in brachial artery flow-mediated dilation from baseline to 2, 4, 6, 8, 10, and 12 weeks of heat therapy, and 4 and 12 weeks of follow-up.

    Measure of endothelial function

    Measured: 0 weeks, 2 weeks, 4 weeks, 6 weeks, 8 weeks, 10 weeks, 12 weeks, 16 weeks, 24 weeks

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted29 Mar 2022
  2. Study start1 Aug 2022
  3. Primary completion1 Nov 2027 (estimated)
  4. Study completion1 Feb 2028 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase N/A
Primary purpose
Treatment
Allocation
Randomised
Intervention model
Parallel groups
Model description
Randomized, sham controlled (parallel design), single-blind
Masking
Single blind
Who is masked
Investigator
Enrolment
120 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT05300971
Sponsor's protocol ID
21-0433
Status last verified
Oct 2026
First submitted
27 Oct 2021
Last updated
2 Nov 2026
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
No

Publications

  • Brunt VE, Howard MJ, Francisco MA, Ely BR, Minson CT. Passive heat therapy improves endothelial function, arterial stiffness and blood pressure in sedentary humans. J Physiol. 2016 Sep 15;594(18):5329-42. doi: 10.1113/JP272453. Epub 2016 Jun 30.

    PubMed 27270841
  • Oh ES, Opoku G, Darvish S, Craighead DH, Ostrow A, Rossman MJ, Steele CN, Struemph T, You Z, Seals DR, Chonchol M, Nowak KL. Sex Differences in Dementia and Mild Cognitive Impairment in Nondialysis CKD. Clin J Am Soc Nephrol. 2026 Mar 1;21(3):389-400. doi: 10.2215/CJN.0000000922. Epub 2025 Nov 20.

    PubMed 41264372

Questions about this trial

What is this clinical trial studying?

A study testing Heat therapy and Thermoneutral water immersion in people with Aging, run by University of Colorado, Boulder at 1 site in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 10 inclusion and 13 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: looking for participants now, as of the sponsor's last update on 2 Nov 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

Contact Vienna E Brunt, PhD (303-724-4898, vienna.brunt@cuanschutz.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Change in casual systolic blood pressure from baseline to 2, 4, 6, 8, 10, and 12 weeks of heat therapy, and 4 and 12 weeks of follow-up. (time frame: 0 weeks, 2 weeks, 4 weeks, 6 weeks, 8 weeks, 10 weeks, 12 weeks, 16 weeks, 24 weeks). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT05300971, which also lists 2 linked publications.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 2 Nov 2026.

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