Aging, Beta Blockers, and Thermoregulatory Responses

This study will test the hypothesis that the drugs propranolol and metoprolol will result in greater increases in core body temperature during 3 hours of extreme heat exposure in older adults.

Study Overview

• Status: Recruiting
• Conditions: Aging; Heat Stress
• Intervention / Treatment: Other: Ambient Heat

Detailed Description

Older individuals are more likely to die or become ill during heat waves. During the 1995 Chicago heat wave, there was 35% increase in hospital admissions for individuals older than 65 years of age. Moreover, adults over the age of 65 have a heat-related death rate that is more than double any other age group. Therefore, with an increasing elderly population that is expected to rise by 60% (to 78 million) by 2035, the causes of this excess mortality must be understood to better protect the ageing United States population. It is notable that selective and non-selective beta blocker drugs are commonly prescribed to older individuals with cardiovascular diseases. In younger individuals exposed to a heat stress, beta blocker administration reduced whole-body sweat rate and skin blood flow responses resulting in greater increases in core body temperature. Notably, nothing is known regarding the effects of beta blockers on thermoregulatory responses during heat exposure in older individuals.

This project will evaluate core body temperature responses to selective and non-selective beta blocker drugs during simulated heat wave exposure in older individuals.

• Study Type: Interventional
• Enrollment (Estimated): 22
• Phase: Phase 4

Contacts and Locations

• Study Contact: Name: Courtney Kirby, RN; Phone Number: 214-345-6502; Email: courtneykirby@texashealth.org
• Study Contact Backup: Name: Erin Harper, MS; Phone Number: 214-345-4737; Email: erinharper@texashealth.org

Study Locations

• United States
  • Texas
    • Dallas, Texas, United States, 75231
      • Recruiting
      • IEEM Texas Health Presbyterian Hospital Dallas
      • Principal Investigator: Craig Crandall, PhD
      • Contact: Taysom Wallace, MS; Phone Number: 214-345-5022; Email: taysomwallace@texashealth.org
      • Contact: Courtney Kirby, RN; Phone Number: 214-345-6502; Email: courtneykirby@texashealth.org

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Healthy and free of any significant medical problems
• Normal resting electrocardiogram
• 65+ years of age
• Controlled cholesterol of less than 200 mg/dl
• Controlled blood pressure of less than 140/90 mmHg

Exclusion Criteria:

• Known diseases or other chronic conditions requiring regular medical therapy including cancer, diabetes, neurological diseases, uncontrolled hypertension, and uncontrolled hypercholesterolemia
• Serious abnormalities detected on routine screening
• Taking prescribed medications or over-the-counter medications that have known influences on either cardiac function or sweating
• Current smokers, as well as individuals who regularly smoked within the past 3 years
• body mass index ≥31 kg/m2

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Double

Number of Arms

6

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Placebo, then Propranolol, then Metoprolol	Other: Ambient Heat; Subjects will spend 3-hours in a heat chamber at 41°C and 40% humidity.
Experimental: Placebo, then Metoprolol, then Propranolol	Other: Ambient Heat; Subjects will spend 3-hours in a heat chamber at 41°C and 40% humidity.
Experimental: Propranolol, then Placebo, then Metoprolol	Other: Ambient Heat; Subjects will spend 3-hours in a heat chamber at 41°C and 40% humidity.
Experimental: Propranolol, then Metoprolol, then Placebo	Other: Ambient Heat; Subjects will spend 3-hours in a heat chamber at 41°C and 40% humidity.
Experimental: Metoprolol, then Placebo, then Propranolol	Other: Ambient Heat; Subjects will spend 3-hours in a heat chamber at 41°C and 40% humidity.
Experimental: Metoprolol, then Propranolol, then Placebo	Other: Ambient Heat; Subjects will spend 3-hours in a heat chamber at 41°C and 40% humidity.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Internal temperature	The change in internal temperature to the 3-hour heat exposure will be measured.	Continuously throughout the 3-hour heat exposure.
Whole body sweat rate	Whole body sweat rate will be measured via changes in pre/post nude body mass.	Nude body mass will be measured before and after the 3-hour heat exposure.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Heart rate	Heart rate will be measured via electrocardiogram.	Continuously throughout the 3-hour heat exposure.
Arterial blood pressure	Systolic and diastolic arterial blood pressures will be measured via a brachial blood pressure cuff.	Continuously throughout the 3-hour heat exposure.

Collaborators and Investigators

• Sponsor: University of Texas Southwestern Medical Center
• Investigators: Principal Investigator: Craig Crandall, PhD, Univ of Texas Southwestern Med Ctr

Study record dates

Study Major Dates

• Study Start (Actual): October 4, 2024
• Primary Completion (Estimated): September 30, 2026
• Study Completion (Estimated): September 30, 2026

Study Registration Dates

• First Submitted: August 30, 2024
• First Submitted That Met QC Criteria: August 30, 2024
• First Posted (Actual): September 3, 2024

Study Record Updates

• Last Update Posted (Estimated): October 23, 2025
• Last Update Submitted That Met QC Criteria: October 21, 2025
• Last Verified: October 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Wounds and Injuries; Heat Stress Disorders
• Other Study ID Numbers: STU-2024-0644

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes