Aging, Hyperthermia
Conditions
Keywords
aging, heat wave, cardiovascular
Brief summary
The purpose of this study is to assess the cardiovascular responses of the elderly to heat wave conditions
Detailed description
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) and 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
Interventions
OTHERHot and Humid Trial
Individuals will be exposed to a simulated heat wave (hot and humid) condition.
OTHERHot and Dry Trial
Individuals will be exposed to a simulated heat wave (hot and dry) condition.
Sponsors
American Heart Association
National Institute on Aging (NIA)
University of Texas Southwestern Medical Center
Study design
Allocation
NON_RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in Core Body Temperature | Prior to and after the 3-hour simulated heat wave exposure. | Core body temperature will be measured via a telemetric pill or rectal temperature probe. |
| Change in Peak Mitral Annular Systolic Velocity (S') | Prior to, during, and after each simulated heat wave exposure; approximately 20 min each | Change in peak mitral annular systolic velocity was measured by tissue doppler imaging. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Ending Skin Temperature | At the end of the 3-hour simulated heat wave exposure. | Skin temperature will be measured from small temperature sensitive electrodes attached to the participant's skin. |
| Ending Heart Rate | At the end of the 3-hour simulated heat wave exposure. | Heart rate will be measured via ECG electrodes attached to the participant |
| Ending Mean Arterial Pressure | At the end of the 3-hour simulated heat wave exposure. | Arterial blood pressure will be measured using a standard arm blood pressure cuff. |
| Change in Cardiac Output | Prior to and after the 3-hour simulated heat wave exposure. | Cardiac output (how much blood is ejected from the heart per minute) was measured using echocardiography. |
Countries
United States
Participant flow
Pre-assignment details
18 participants were either screened out or withdrew before randomization.
Participants by arm
| Arm | Count |
|---|---|
| Younger Participants: Hot and Humid First, Then Hot and Dry Individuals aged 18-39 years that had the hot/humid trial first and the hot/dry trial second. | 9 |
| Younger Participants: Hot and Dry First, Then Hot and Humid Individuals aged 18-39 years that had the hot/dry trial first and the hot/humid trial second. | 11 |
| Older Participants: Hot and Humid First, Then Hot and Dry Individuals aged 65 years or older that had the hot/humid trial first and the hot/dry trial second. | 8 |
| Older Participants: Hot and Dry First, Then Hot and Humid Individuals aged 65 years or older that had the hot/dry trial first and the hot/humid trial second. | 12 |
| Total | 40 |
Withdrawals & dropouts
| Period | Reason | FG000 | FG001 | FG002 | FG003 |
|---|---|---|---|---|---|
| Washout (1 Week) | Withdrawal by Subject | 0 | 0 | 0 | 1 |
Baseline characteristics
| Characteristic | Younger Participants: Hot and Humid First, Then Hot and Dry | Total | Older Participants: Hot and Dry First, Then Hot and Humid | Older Participants: Hot and Humid First, Then Hot and Dry | Younger Participants: Hot and Dry First, Then Hot and Humid |
|---|---|---|---|---|---|
| Age, Continuous | 30 years STANDARD_DEVIATION 6 | 50 years STANDARD_DEVIATION 21 | 71 years STANDARD_DEVIATION 4 | 70 years STANDARD_DEVIATION 4 | 29 years STANDARD_DEVIATION 4 |
| Ethnicity (NIH/OMB) Hispanic or Latino | 1 Participants | 3 Participants | 0 Participants | 1 Participants | 1 Participants |
| Ethnicity (NIH/OMB) Not Hispanic or Latino | 8 Participants | 37 Participants | 12 Participants | 7 Participants | 10 Participants |
| Ethnicity (NIH/OMB) Unknown or Not Reported | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) American Indian or Alaska Native | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) Asian | 2 Participants | 4 Participants | 0 Participants | 0 Participants | 2 Participants |
| Race (NIH/OMB) Black or African American | 1 Participants | 6 Participants | 1 Participants | 1 Participants | 3 Participants |
| Race (NIH/OMB) More than one race | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) Native Hawaiian or Other Pacific Islander | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) Unknown or Not Reported | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) White | 6 Participants | 30 Participants | 11 Participants | 7 Participants | 6 Participants |
| Region of Enrollment United States | 9 participants | 40 participants | 12 participants | 8 participants | 11 participants |
| Sex: Female, Male Female | 4 Participants | 20 Participants | 4 Participants | 6 Participants | 6 Participants |
| Sex: Female, Male Male | 5 Participants | 20 Participants | 8 Participants | 2 Participants | 5 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk | EG002 affected / at risk | EG003 affected / at risk |
|---|---|---|---|---|
| deaths Total, all-cause mortality | 0 / 20 | 0 / 21 | 0 / 20 | 0 / 20 |
| other Total, other adverse events | 0 / 20 | 0 / 21 | 0 / 20 | 0 / 20 |
| serious Total, serious adverse events | 0 / 20 | 0 / 21 | 0 / 20 | 0 / 20 |
Outcome results
Primary
Change in Core Body Temperature
Core body temperature will be measured via a telemetric pill or rectal temperature probe.
Time frame: Prior to and after the 3-hour simulated heat wave exposure.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Younger Participants- Hot and Dry | Change in Core Body Temperature | .68 degrees Celsius (°C) | Standard Deviation 0.27 |
| Older Participants- Hot and Dry | Change in Core Body Temperature | 1.37 degrees Celsius (°C) | Standard Deviation 0.42 |
| Younger Participants: Hot and Humid | Change in Core Body Temperature | .58 degrees Celsius (°C) | Standard Deviation 0.25 |
| Older Participants: Hot and Humid | Change in Core Body Temperature | 1.02 degrees Celsius (°C) | Standard Deviation 0.32 |
Primary
Change in Peak Mitral Annular Systolic Velocity (S')
Change in peak mitral annular systolic velocity was measured by tissue doppler imaging.
Time frame: Prior to, during, and after each simulated heat wave exposure; approximately 20 min each
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Younger Participants- Hot and Dry | Change in Peak Mitral Annular Systolic Velocity (S') | 1.46 cm/s | Standard Deviation 1.54 |
| Older Participants- Hot and Dry | Change in Peak Mitral Annular Systolic Velocity (S') | 3.33 cm/s | Standard Deviation 2.05 |
| Younger Participants: Hot and Humid | Change in Peak Mitral Annular Systolic Velocity (S') | 1.39 cm/s | Standard Deviation 1.31 |
| Older Participants: Hot and Humid | Change in Peak Mitral Annular Systolic Velocity (S') | 2.09 cm/s | Standard Deviation 1.29 |
Secondary
Change in Cardiac Output
Cardiac output (how much blood is ejected from the heart per minute) was measured using echocardiography.
Time frame: Prior to and after the 3-hour simulated heat wave exposure.
Population: It should be known that only 16 participants in the hot/dry trials (younger and older) and the hot/humid trial (younger) and only 14 participants in the hot/humid trial (older) were analyzed due to missing data/equipment malfunction.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Younger Participants- Hot and Dry | Change in Cardiac Output | .88 L/min | Standard Deviation 0.77 |
| Older Participants- Hot and Dry | Change in Cardiac Output | .75 L/min | Standard Deviation 0.82 |
| Younger Participants: Hot and Humid | Change in Cardiac Output | .38 L/min | Standard Deviation 0.52 |
| Older Participants: Hot and Humid | Change in Cardiac Output | .76 L/min | Standard Deviation 0.96 |
Secondary
Ending Heart Rate
Heart rate will be measured via ECG electrodes attached to the participant
Time frame: At the end of the 3-hour simulated heat wave exposure.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Younger Participants- Hot and Dry | Ending Heart Rate | 82 beats per minute (bpm) | Standard Deviation 9 |
| Older Participants- Hot and Dry | Ending Heart Rate | 87 beats per minute (bpm) | Standard Deviation 15 |
| Younger Participants: Hot and Humid | Ending Heart Rate | 80 beats per minute (bpm) | Standard Deviation 10 |
| Older Participants: Hot and Humid | Ending Heart Rate | 81 beats per minute (bpm) | Standard Deviation 14 |
Secondary
Ending Mean Arterial Pressure
Arterial blood pressure will be measured using a standard arm blood pressure cuff.
Time frame: At the end of the 3-hour simulated heat wave exposure.
Population: It should be noted that only 19 participants were analyzed in the Hot/Humid arm because of missing data/equipment issues.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Younger Participants- Hot and Dry | Ending Mean Arterial Pressure | 77 mmHg | Standard Deviation 7 |
| Older Participants- Hot and Dry | Ending Mean Arterial Pressure | 76 mmHg | Standard Deviation 10 |
| Younger Participants: Hot and Humid | Ending Mean Arterial Pressure | 78 mmHg | Standard Deviation 5 |
| Older Participants: Hot and Humid | Ending Mean Arterial Pressure | 76 mmHg | Standard Deviation 8 |
Secondary
Ending Skin Temperature
Skin temperature will be measured from small temperature sensitive electrodes attached to the participant's skin.
Time frame: At the end of the 3-hour simulated heat wave exposure.
Population: It should be noted that only 17 older participants for the hot/dry trial and 19 participants for the hot/humid trial were analyzed due to missing data/equipment issues.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Younger Participants- Hot and Dry | Ending Skin Temperature | 37.57 degrees Celsius (°C) | Standard Deviation 0.73 |
| Older Participants- Hot and Dry | Ending Skin Temperature | 37.37 degrees Celsius (°C) | Standard Deviation 0.85 |
| Younger Participants: Hot and Humid | Ending Skin Temperature | 36.65 degrees Celsius (°C) | Standard Deviation 0.83 |
| Older Participants: Hot and Humid | Ending Skin Temperature | 36.05 degrees Celsius (°C) | Standard Deviation 0.58 |