Chronic Heat Therapy for Improving Vascular Health

Cardiovascular Diseases Clinical Trial

— CHT  

Official title:

Chronic Heat Therapy for Improving Biomarkers of Vascular Health in Young, Healthy, Humans

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT02518399
• Other study ID #: 09272013.025
• Secondary ID: 14PRE20380300
• Status: Completed
• Phase: N/A
• First received: July 23, 2015
• Last updated: October 24, 2017
• Start date: April 2013
• Est. completion date: April 30, 2016

Study information

• Verified date: October 2017
• Source: University of Oregon
• Contact: n/a
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial Summary

The purpose of the study is to investigate whether long-term heat therapy (i.e. 8 weeks of hot tub 4-5x per week) improves biomarkers of cardiovascular health in young, healthy, able-bodied individuals. Although exercise is a potent means of improving cardiovascular health, many patients are unable to exercise effectively, and thus there is high demand for novel therapies to better manage cardiovascular risk in these patients. If successful, this study will set the groundwork for heat therapy to be used as an alternative treatment in patients who have limited exercise capabilities for the prevention of cardiovascular disease.

Description:

Exercise training is a potent means of improving cardiovascular (CV) risk; however, exercise is challenging for many patient populations. Passive heat therapy may provide a simple and effective alternative to exercise for improving CV health, and no one has yet studied the physiological benefits of chronic heat exposure in humans. Heat exposure induces the expression of heat shock proteins, which can have a multitude of beneficial effects on the CV system, many of which are common to exercise training. In particular, these benefits include upregulation of many cellular pathways associated with improved vascular function, a predominant contributor to CV health. The goal of the study is to determine the effects of chronic passive heat therapy on vascular function in young, healthy, able-bodied individuals. The investigators will perform a randomized-controlled trial in which subjects participate in 8 weeks of either heat therapy or thermoneutral water immersion (sham). Heat therapy will entail 8 weeks of hot water immersion sufficient to raise core temperature >38.5°C for 1h, 4-5 times per week. Thermoneutral water immersion will entail 8 weeks of immersion in 36°C water for the same duration as heat therapy. In both subject groups, the investigators will measure various well-established biomarkers of vascular function before and after 8 weeks of heat therapy, including measures of arterial stiffness (arterial compliance, beta-stiffness, and pulse wave velocity), endothelium-dependent dilation (flow-mediated dilation), and intima media thickness. The investigators will investigate the effects of heat therapy on the microvasculature and on the mechanisms behind improvements in vascular function in the cutaneous microcirculation, an ideal site for pharmacodissecting the molecular pathways involved, using microdialysis paired with laser-Doppler flowmetry. If successful, these studies will serve as a basis for developing heat therapy as a novel means of improving CV risk, which has the potential to reshape the treatment of patient populations with limited exercise capabilities.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 20
• Est. completion date: April 30, 2016
• Est. primary completion date: September 2015
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: All
• Age group: 18 Years to 40 Years

Eligibility

Inclusion Criteria:

• Young, healthy, able-bodied

Exclusion Criteria:

• Diagnosis of any chronic diseases related to the cardiovascular system (e.g. hypertension, cardiovascular disease, diabetes, etc.),

• Currently taking prescription medications (except contraceptives)

• Body mass index over 27 kg/m2

• Current smoking

• Currently pregnant or breast-feeding

Related Conditions & MeSH terms

• Cardiovascular Diseases

Intervention

Other:
• Heat therapy
Subjects will report to the laboratory 4-5x per week for 8 weeks (36 sessions total) for heat therapy sessions. In each session, subjects will be immersed in a 40°C hot tub for up to 90min in order to increase body core temperature to 38.5°C and, once there, maintain it between 38.5-39.0°C for 60min.
• Thermoneutral water immersion
Subjects will report to the laboratory 4-5x per week for 8 weeks (36 sessions total) for thermoneutral water immersion sessions. In each session, subjects will be immersed in a 36°C tub for 90min in order to maintain body core temperature at a constant level.

Locations

Country	Name	City	State
United States	University of Oregon	Eugene	Oregon

Sponsors (1)

Lead Sponsor	Collaborator
University of Oregon

Country where clinical trial is conducted

United States, 

References & Publications (1)

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. — View Citation

Outcome

Type	Measure	Description	Time frame	Safety issue
Other	Carotid dynamic arterial compliance	Change in compliance of the common carotid artery relative to blood pressure, measured using ultrasonography-tonometry. This is a measure of arterial stiffness.	8 weeks
Primary	Change in flow-mediated dilation	The change in percent dilation of the brachial artery following release of a 5-min arterial occlusion, measured using ultrasonography. This test is highly prognostic of cardiovascular risk and mortality.	8 weeks
Primary	Femoral dynamic arterial compliance	The change in compliance of the superficial femoral artery relative to blood pressure, measured using ultrasonography-tonometry. This is a measure of arterial stiffness.	8 weeks
Primary	Intima media thickness	Change in wall thickness of the common carotid artery, measured using ultrasonography. This is predictive of future development of cardiovascular disease, in particular, atherosclerosis.	8 weeks
Primary	Mean arterial blood pressure	Change in blood pressure measured using brachial oscillation following >20 min supine rest.	8 weeks
Secondary	Cutaneous nitric oxide-dependent dilation	Change in the difference between cutaneous microdialysis sites receiving a nitric oxide inhibitor (L-NNA, IND # 124,303) and Lactated Ringer's (control). Measured using laser-Doppler flowmetry during a local heating protocol.	8 weeks