Heat Exposure for Aging

Overseen By Glen P Kenny, PhD

Age: 65+

Sex: Female

Trial Phase: Academic

Sponsor: University of Ottawa

Disqualifiers: Severe hypoglycemia, Uncontrolled hypertension, Serious diabetes complications, Cardiac abnormalities, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: 5

12 Participants Needed

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial aims to study how older women respond to extreme heat and determine the limits at which their bodies can no longer effectively cool down. Researchers will use a humidity-ramp protocol, a method that gradually increases heat and humidity, to monitor changes in participants' core temperatures. The results will help identify specific conditions that become dangerous and assess the impact on heart health, mental well-being, and cognitive function. Participants should be women aged 65 or older, non-smokers, and either have or not have controlled high blood pressure or type 2 diabetes for at least five years. As an unphased study, this trial offers participants the opportunity to contribute to important research that could improve health guidelines for older adults.

Do I need to stop taking my current medications for the trial?

The trial protocol does not specify if you need to stop taking your current medications, but it mentions that changes in medication could make participation inadvisable. It's best to discuss your specific medications with the trial investigators.

What prior data suggests that the humidity-ramp protocol is safe for older females?

Research shows that heat poses risks, especially for older adults. Studies have found that extreme heat can accelerate aging and worsen health problems in seniors. For those over 65, heat can cause serious issues like increased heart rate and body temperature. This is even more noticeable in older women, who may struggle more to cool down.

Regarding the safety of the humidity-ramp protocol, research is examining its effectiveness. This method involves gradually increasing humidity levels while monitoring body temperature to find the point where the body can no longer cool itself properly. While this method is gaining popularity, researchers continue to study its accuracy in identifying this limit.

For fixed-condition heat exposures, studies support using these methods to assess how well older adults can handle heat. These studies help understand the body's limits and ensure safety by identifying manageable heat levels.

In summary, while heat exposure can be dangerous, these studies aim to find safe limits for older adults, especially women. The research is ongoing, but the methods are carefully designed to minimize risks. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Researchers are excited about the Heat Exposure for Aging trial because it explores how different heat exposure protocols might impact aging. Traditional methods for managing aging-related conditions often focus on medications and lifestyle changes, but this trial is investigating the potential benefits of controlled heat exposure. This approach is unique because it uses a humidity-ramp protocol and various fixed-condition heat exposures to see how they might affect the body's response to heat as we age. By focusing on how the body reacts to heat and humidity, researchers hope to uncover new ways to improve health and well-being in older adults without relying solely on pharmaceuticals.

What evidence suggests that this trial's treatments could be effective for older females facing heat-related risks?

Research shows that older adults are more vulnerable to heat, which can accelerate aging and affect health. Studies have found that extreme heat can cause the body to age faster, similar to the effects of smoking. Over time, this can lead to more age-related health problems. In this trial, all participants will first undergo the humidity-ramp protocol, which helps identify when heat becomes dangerous, especially for older individuals. This test assesses how well the body can handle rising heat and humidity, providing insight into the heat limits for older women. Understanding these limits is crucial to preventing health risks from extreme heat. ^{1 4 5 6 7}

Who Is on the Research Team?

Glen P Kenny, PhD

Principal Investigator

University of Ottawa

Are You a Good Fit for This Trial?

This trial is for older females aged 65 or above who are generally healthy. It's designed to understand how they cope with extreme heat, which is important because of climate change and the higher risk of heat-related illnesses in this group. Participants should not have conditions that affect their body's temperature regulation.

Inclusion Criteria

I can speak English or French.

Ability to provide informed consent

Non-smoking

Exclusion Criteria

My disease limits my physical activities.

I've had severe low blood sugar or can't tell when my sugar is low in the last year.

Cardiac abnormalities identified during screening

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Ramping Protocol

Participants rest at 42°C, 28% RH for 70 minutes, followed by incremental RH increases to 70% RH to identify core temperature inflection points.

Up to 2.5 hours

1 visit (in-person)

Fixed Condition Trials

Participants undergo randomized fixed-condition heat exposures at various levels relative to their inflection point.

9 hours per trial

4 visits (in-person)

Follow-up

Participants are monitored for safety and effectiveness after heat exposure trials.

4 weeks

What Are the Treatments Tested in This Trial?

Interventions

• Above-inflection fixed-condition exposure (5%)
• Below-inflection fixed-condition exposure (10%)
• Below-inflection fixed-condition exposure (5%)
• Control fixed-condition exposure
• Humidity-Ramp Protocol

Trial Overview The study tests how older women handle different levels of heat and humidity. They'll go through five trials: one where humidity increases gradually, and four others at fixed conditions around a critical temperature point identified from the first trial. The goal is to see if gradual exposure accurately shows when the body can't cool itself anymore.

How Is the Trial Designed?

Group I: Humidity-ramp protocol Experimental Treatment 1 Intervention

The humidity-ramp protocol will necessarily be performed first. The order of the fixed-condition exposures will be randomized.

Group II: Below-inflection fixed-condition heat exposure (5%) Experimental Treatment 1 Intervention

Participants will complete all exposures. The humidity-ramp protocol will necessarily be performed first. The order of the fixed-condition exposures will be randomized.

Group III: Below-inflection fixed-condition heat exposure (10%) Experimental Treatment 1 Intervention

Participants will complete all exposures. The humidity-ramp protocol will necessarily be performed first. The order of the fixed-condition exposures will be randomized.

Group IV: Above-inflection fixed-condition heat exposure (5%) Experimental Treatment 1 Intervention

Participants will complete all exposures. The humidity-ramp protocol will necessarily be performed first. The order of the fixed-condition exposures will be randomized.

Group V: Control fixed-condition heat exposure Active Control 1 Intervention

Participants will complete all exposures. The humidity-ramp protocol will necessarily be performed first. The order of the fixed-condition exposures will be randomized.

Who Is Running the Clinical Trial?

University of Ottawa

Lead Sponsor

Trials

231

Recruited

267,000+

Citations

1. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC10860513/

Population Aging and Heat Exposure in the 21st Century The co-occurring trends of population aging and climate change mean that rising numbers of U.S. older adults are at risk of intensifying heat exposure.

2. gero.usc.edu gero.usc.edu/2025/02/26/study-extreme-heat-may-speed-up-aging-in-older-adults/

Study: Extreme Heat May Speed Up Aging in Older Adults A new USC Leonard Davis School of Gerontology study suggests greater exposure to extreme heat may accelerate biological aging in older adults.

3. npr.org npr.org/2025/03/17/nx-s1-5325273/heat-accelerates-aging-new-study-finds

Heat can age you as much as smoking, a new study finds A new study published in Science Advances shows that prolonged heat exposure of that magnitude can even modify how people's genes behave, speeding up aging.

4. nytimes.com nytimes.com/2025/08/25/climate/heat-waves-aging.html

New Study Shows Heat Waves Make People Age Faster Exposure to heat waves over just two years could add up to 12 extra days of age-related health damage.

5. aarp.org aarp.org/health/conditions-treatments/extreme-heat-accelerates-aging/

How Extreme Heat Can Speed Up Aging A recent study has shown that ongoing exposure to heat over 80 degrees accelerates biological aging, even more than smoking.

6. academic.oup.com academic.oup.com/biomedgerontology/article/79/4/glae053/7636183

Population Aging and Heat Exposure in the 21st Century Extensive research has documented how extreme heat, in particular, exacerbates older adults' morbidity, mortality, and mental health problems (9 ...

7. pnas.org pnas.org/doi/10.1073/pnas.2421281122

Validating new limits for human thermoregulation While exposure to Twb above the core temperature inflection point was uncompensable, our data are less clear as to whether conditions were ...