Identification of Critical Thermal Environments for Aged Adults

This study evaluates critical environmental limits (temperature and humidity) above which older adults are unable to effectively thermoregulate. Participants will exercise in a series of different environmental conditions to identify combinations of temperature and humidity above which age-related physiological changes cause uncompensable heat stress, resulting in increased risk of heat illness.

Study Overview

• Status: Recruiting
• Conditions: Aging
• Intervention / Treatment: Other: Control; Drug: Low dose ASA

Detailed Description

The earth's climate is warming well above historical averages, and there is an increased frequency, duration, and severity of heat waves. At the same time, the world's population is rapidly aging. Aging is associated with reductions in thermoregulatory capacity due to reductions in sweating and skin blood flow. For this reason, people ≥65 years exhibit exponentially larger increases in morbidity and mortality during heat waves than younger individuals, with the large majority of excess deaths during heat waves occurring in the elderly.

Compounding the physiological effects of primary aging, co-morbidities and common classes of drugs taken by older adults can further compromise their thermoregulatory function. One such class of medications is cyclooxygenase inhibitors, including aspirin (ASA) and other platelet inhibitors. Provocative data published by our lab indicate that platelet inhibitors including ASA increase the rate of heat storage during passive heat stress by ~25%. Following current clinical guidelines, nearly 40% of US adults over the age of 50 engage in an aspirin therapy regiment for the primary or secondary prevention of cardiovascular disease.

Although there is compelling evidence that aging is associated with decreased heat dissipation and elevated risk of heat illness in hot ambient conditions, the significant question remains: In what specific environments does this age disparity begin to occur? The goal of the current study is to identify and model ambient conditions that are unsafe for older adults. A second aim of the study is to determine the effects of the commonly used platelet inhibitor, acetylsalicylic acid (ASA), on age-specific critical environmental limits.

• Study Type: Interventional
• Enrollment (Estimated): 190
• Phase: Early Phase 1

Contacts and Locations

• Study Contact: Name: Lacy M Alexander, Ph.D.; Phone Number: 8148671781; Email: lma191@psu.edu

Study Locations

• United States
  • Pennsylvania
    • University Park, Pennsylvania, United States, 16802
      • Recruiting
      • Noll Laboratory
      • Contact: W. Larry Kenney, Ph.D.; Phone Number: 814-863-1672; Email: w7k@psu.edu
      • Contact: S. Tony Wolf, Ph.D.; Phone Number: 814-863-8557; Email: saw85@psu.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 16 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Adults aged 18 and older (those 40+ years of age must be cleared by collaborating physician)
• All premenopausal women will be eumenorrheic (by survey)
• Asymptomatic and no signs/symptoms of disease according to the American College of Sports Medicine 10th edition Guidelines for Exercise Testing and Prescription

Exclusion Criteria:

• Medications that affect thermoregulatory or cardiovascular responses to exercise
• Any contraindications to low intensity physical activity on the Physical Activity Readiness Questionnaire
• Any mobility restrictions that interfere with low intensity physical activity
• Pregnant or planning to become pregnant in the next 12 months
• Prior diagnosis of cancer, cardiovascular disease, diabetes, or metabolic syndrome
• Illegal/recreational drug use
• History of Chron's disease, diverticulitis, or similar gastrointestinal disease
• Abnormal resting or exercise electrocardiogram (ECG)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Critical Environmental Limits; Subjects will perform exercise at ~200-300W with ambient temperature or humidity increasing every 5 min throughout the trial until core temperature begins to rise.	Other: Control; All participants will be tested with no treatment.
Experimental: Aspirin Supplementation; After a minimum of 7 days of daily, low-dose aspirin ingestion, older subjects will repeat critical environmental limits trials. As before, subjects will perform exercise at ~200-300W with ambient temperature or humidity increasing every 5 min throughout the trial until core temperature begins to rise.	Drug: Low dose ASA; A sub-group of older adults will be re-tested after 7 days of treatment with low-dose aspirin.; Other Names: Low-dose aspirin

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Temperature and humidity limits for maintaining stable core temperature	Core temperature will be measured throughout exercise. The point at which heat stress becomes uncompensable will be determined for each environmental and exercise condition by assessing the combination of temperature and humidity at which core temperature begins to rise.	Through study completion, an average of 1 year.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Core temperature	Core temperature will be monitored throughout each experimental visit	Continuous throughout visit until completion of exercise; an average of 2 hours.
Sweat rate	Sweat rate will be determined by measuring nude body mass before and after each experimental visit	Immediately before and immediately after exercise.
Skin temperature	Skin temperature will be monitored throughout each experimental visit	Continuous throughout visit until completion of exercise; an average of 2 hours.

Collaborators and Investigators

• Sponsor: Penn State University
• Investigators: Principal Investigator: W. Larry Kenney, Ph.D., The Pennsylvania State University

Study record dates

Study Major Dates

• Study Start (Actual): December 30, 2020
• Primary Completion (Estimated): February 28, 2025
• Study Completion (Estimated): February 28, 2025

Study Registration Dates

• First Submitted: February 20, 2020
• First Submitted That Met QC Criteria: February 24, 2020
• First Posted (Actual): February 25, 2020

Study Record Updates

• Last Update Posted (Estimated): February 6, 2024
• Last Update Submitted That Met QC Criteria: February 5, 2024
• Last Verified: February 1, 2024

More Information

Terms related to this study

• Keywords: Aging; Thermoregulation; Heat stress
• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Molecular Mechanisms of Pharmacological Action; Peripheral Nervous System Agents; Enzyme Inhibitors; Analgesics; Sensory System Agents; Anti-Inflammatory Agents, Non-Steroidal; Analgesics, Non-Narcotic; Anti-Inflammatory Agents; Antirheumatic Agents; Fibrinolytic Agents; Fibrin Modulating Agents; Platelet Aggregation Inhibitors; Cyclooxygenase Inhibitors; Antipyretics; Aspirin
• Other Study ID Numbers: Study14062

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