Cardiovascular Responses to Heat Waves in the Elderly

Study Overview
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Brief Summary
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The purpose of this study is to assess the cardiovascular responses of the elderly to heat wave conditions

Detailed Description
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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

Official Title
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Heat Waves in the Elderly: Reducing Thermal and Cardiovascular Consequences

Conditions
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Aging, Hyperthermia

Intervention / Treatment
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* Other: Simulated heat wave


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Younger participants<br>Individuals aged 18-39 years | Other: Simulated heat wave<br>* Individuals will be exposed to thermoneutral climate conditions and two simulated heat wave conditions.<br>|
| Older participants<br>Individuals aged 65 years or older | Other: Simulated heat wave<br>* Individuals will be exposed to thermoneutral climate conditions and two simulated heat wave conditions.<br>|

What is the study measuring?
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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 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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aging, heat wave, cardiovascular