Clinical trial NCT04284397: Identification of Critical Thermal Environments for Aged Adults
Official title: Identification of Critical Thermal Environments for Aged Adults
Study type: INTERVENTIONAL
Overall status: RECRUITING
Phase: EARLY_PHASE1
Conditions: Aging
Keywords: Aging
Thermoregulation
Heat stress
Lead sponsor: Penn State University
Sponsor class: OTHER
First posted: 2020-02-25
Enrollment: 190
Sex: ALL
Minimum age (years): 18
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: SINGLE_GROUP
Intervention model description: Two groups of subjects (young, older) participate in twelve experiments; experimental conditions consist of six different combinations of temperature and humidity and are performed at two different exercise intensities. The experiments are conducted in randomized order and are separated by a minimum of three days. A subgroup of older adults will be asked to complete all trials after taking daily low-dose aspirin for seven days, and aspirin will be continued until all trials are complete.
Primary purpose: BASIC_SCIENCE

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.

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)

Primary outcomes:
measure: Temperature and humidity limits for maintaining stable core temperature
timeFrame: Through study completion, an average of 1 year.
Secondary outcomes:
measure: Core temperature
timeFrame: Continuous throughout visit until completion of exercise; an average of 2 hours.
measure: Sweat rate
timeFrame: Immediately before and immediately after exercise.
measure: Skin temperature
timeFrame: Continuous throughout visit until completion of exercise; an average of 2 hours.
Other outcomes:
Locations:
city: University Park
country: United States
facility: Noll Laboratory
state: Pennsylvania
Study officials:
affiliation: The Pennsylvania State University
name: W. Larry Kenney, Ph.D.
role: PRINCIPAL_INVESTIGATOR
References: