Identification of Critical Thermal Environments for Aged Adults

NCT ID: NCT04284397

Last Updated: 2026-01-27

Basic Information

• Recruitment Status: RECRUITING
• Clinical Phase: EARLY_PHASE1
• Total Enrollment: 190 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2020-12-30
• Study Completion Date: 2027-02-27

Brief Summary

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.

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.

Conditions

Aging

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: SINGLE_GROUP
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: NONE

Study Groups

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.

Group Type: EXPERIMENTAL

Control

Intervention Type: OTHER

All participants will be tested with no treatment.

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.

Group Type: EXPERIMENTAL

Low dose ASA

Intervention Type: DRUG

A sub-group of older adults will be re-tested after 7 days of treatment with low-dose aspirin.

Interventions

Low dose ASA

A sub-group of older adults will be re-tested after 7 days of treatment with low-dose aspirin.

Intervention Type: DRUG

Control

All participants will be tested with no treatment.

Intervention Type: OTHER

Other Intervention Names

Low-dose aspirin

Eligibility Criteria

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)

• Minimum Eligible Age: 18 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Penn State University

OTHER

Sponsor Role: lead

Responsible Party

W. Larry Kenney

Professor

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

W. Larry Kenney, Ph.D.

Role: PRINCIPAL_INVESTIGATOR

The Pennsylvania State University

Locations

Noll Laboratory

University Park, Pennsylvania, United States

Site Status: RECRUITING

Countries

United States

Central Contacts

Lacy M Alexander, Ph.D.

Role: CONTACT

lma191@psu.edu

8148671781

Facility Contacts

W. Larry Kenney, Ph.D.

Role: primary

w7k@psu.edu

814-863-1672

S. Tony Wolf, Ph.D.

Role: backup

saw85@psu.edu

814-863-8557

Other Identifiers

Study14062

Identifier Type: -

Identifier Source: org_study_id