Cardiovascular Responses to Heat Waves in the Elderly

Heat Waves in the Elderly: Reducing Thermal and Cardiovascular Consequences

The purpose of this study is to assess the cardiovascular responses of the elderly to heat wave conditions

Study Overview

• Status: Active, not recruiting
• Conditions: Hyperthermia; Aging
• Intervention / Treatment: Other: Simulated heat wave

Detailed Description

Heat waves are lethal and cause a disproportionate number of deaths in the elderly relative to any other age group. It is important to note that such deaths are primarily cardiovascular, not hyperthermia itself, in origin. Nevertheless, we know relatively little about the effects of aging on cardiovascular function during actual heat wave-like conditions. The central hypothesis of this work is that the elderly exhibit greater cardiovascular stress during heat wave conditions. Aim 1 will test the hypothesis that recognized impairments in thermoregulatory capacity in the elderly will culminate in heightened cardiovascular stress during prolonged exposure to heat wave conditions. Comprehensive cardiovascular and thermal responses in the elderly, relative to younger adults, will be evaluated during exposure to two prolonged heat wave conditions: hot and humid (replicating the 1995 Chicago heat wave), very hot and dry (replicating the 2018 Los Angeles heat wave). The expected outcome from this body of work will re-shape our understanding of the consequences of aging on cardiovascular function during heat waves

• Study Type: Observational
• Enrollment (Actual): 50

Contacts and Locations

• Study Contact: Name: Bonnie Orth, MS; Phone Number: 214-345-4737; Email: BonnieOrth@texashealth.org
• Study Contact Backup: Name: Zachary McKenna, PhD; Phone Number: 214-345-4623; Email: zacharymckenna@texashealth.org

Study Locations

• United States
  • Texas
    • Dallas, Texas, United States, 75231
      • Texas Health Presbyterian Hospital Dallas

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

The study population will be healthy younger and older individuals identified from the general population.

Description

Inclusion Criteria:

• Healthy male and female individuals
• 18-35 years or 65+ years of age
• Free of any underlying moderate to serious medical conditions

Exclusion Criteria:

• Known heart disease; other chronic medical conditions requiring regular medical therapy including cancer, diabetes, neurological diseases, uncontrolled hypertension, and uncontrolled hypercholesterolemia.
• Taking of any medications (such as beta blockers and non-dihydropyridine calcium channel blockers) that have known influences on either cardiac function or sweating responses.
• Abnormalities detected on routine screening.
• Individuals who participate in a structured aerobic exercise training program at moderate to high intensities.
• Current smokers, as well as individuals who regularly smoked within the past 3 years.
• Body mass index of greater than 30 kg/m^2
• Pregnant individuals

Study Plan

How is the study designed?

Design Details

• Observational Models: Cohort
• Time Perspectives: Prospective

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Younger participants; Individuals aged 18-39 years	Other: Simulated heat wave; Individuals will be exposed to thermoneutral climate conditions and two simulated heat wave conditions.
Older participants; Individuals aged 65 years or older	Other: Simulated heat wave; Individuals will be exposed to thermoneutral climate conditions and two simulated heat wave conditions.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Core body temperature	Core body temperature will be measured from gastrointestinal temperature via an ingestible telemetric pill.	Prior to and throughout each simulated heat wave exposure; an average of 480 minutes.
Measures of left ventricular function	Measures of left ventricular function, such as ventricular wall motion and ventricular filling, will be obtained from echocardiography images.	Prior to, during, and after each simulated heat wave exposure; approximately 20 min each

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Skin temperature	Skin temperature will be measured from small temperature sensitive electrodes attached to the participant's skin	Prior to and throughout each simulated heat wave exposure; an average of 480 minutes.
Heart rate	Heart rate will be measured from ECG electrodes attached to the participant	Prior to and throughout each simulated heat wave exposure; an average of 480 minutes.
Arterial blood pressure	Arterial blood pressure will be measured using a standard arm blood pressure cuff	Prior to and throughout each simulated heat wave exposure; an average of 480 minutes.
Cardiac output	Cardiac output (how much blood is ejected from the heart) will be measured using echocardiography and nitrous oxide rebreathing approaches.	Prior to, during, and after each simulated heat wave exposure; approximately 20 min each
Cerebral perfusion	Cerebral perfusion will be measured by doppler ultrasound of the internal carotid and vertebral arteries	Prior to, during, and after each simulated heat wave exposure; approximately 20 min each

Collaborators and Investigators

• Sponsor: University of Texas Southwestern Medical Center
• Collaborators: National Institute on Aging (NIA); American Heart Association

Study record dates

Study Major Dates

• Study Start (Actual): January 19, 2021
• Primary Completion (Estimated): August 31, 2026
• Study Completion (Estimated): August 31, 2026

Study Registration Dates

• First Submitted: August 28, 2020
• First Submitted That Met QC Criteria: September 2, 2020
• First Posted (Actual): September 3, 2020

Study Record Updates

• Last Update Posted (Actual): January 31, 2024
• Last Update Submitted That Met QC Criteria: January 29, 2024
• Last Verified: January 1, 2024

More Information

Terms related to this study

• Keywords: aging; cardiovascular; heat wave
• Additional Relevant MeSH Terms: Wounds and Injuries; Body Temperature Changes; Heat Stress Disorders; Hyperthermia
• Other Study ID Numbers: STU_2019_1759; 1R01AG069005-01 (U.S. NIH Grant/Contract)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No