Simulated Heat Exposure for Heat Stress

Overseen By Glen P Kenny, PhD

Age: 18 - 65

Sex: Any

Trial Phase: Academic

Sponsor: University of Ottawa

Disqualifiers: Chronic health conditions, Endurance trained, others

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

Approved in 2 Jurisdictions This treatment is already approved in other countries

Compensation: Varies

Number of Visits: Unknown

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial aims to understand the effects of staying indoors in very hot conditions on the body. Researchers seek to observe changes in heart health and body temperature when young adults face high indoor temperatures, similar to those during the 2021 Western Heat Dome. Participants will spend a few days in a controlled environment set to these hot temperatures, simulating indoor overheating exposure. The trial seeks non-smoking young adults who do not regularly experience high heat, such as from hot baths or saunas, and have no chronic health issues. As an unphased trial, this study offers participants a unique opportunity to contribute to important research on heat exposure and health.

Will I have to stop taking my current medications?

The trial protocol does not specify whether you need to stop taking your current medications. However, since the trial excludes people with chronic health conditions, it might imply that participants should not be on regular medication for such conditions.

What prior data suggests that this simulated indoor overheating exposure is safe for participants?

Research shows that hot indoor environments can cause health problems. Studies have found that prolonged exposure to heat can lead to heat stress, affecting the heart and lungs. For instance, individuals might experience breathing difficulties or increased heart strain.

One study examined older adults' reactions to hot indoor conditions and found potential health issues. Other reviews have noted that excessive heat can cause serious problems, such as heat stroke or even death if not managed properly.

In summary, while exact risks may vary, clear evidence indicates that very hot indoor environments can be harmful. Prospective study participants should be aware of these potential risks. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Researchers are excited about this trial because it explores how the human body responds to prolonged indoor heat exposure, simulating an extreme heat event. Unlike traditional studies that focus on quick, high-temperature exposure, this trial involves a more realistic, daylong exposure to moderate indoor heat levels. This approach could provide new insights into how extended heat stress affects young adults, potentially leading to improved guidelines for managing heat-related health risks in increasingly warmer climates.

What evidence suggests that simulated indoor overheating exposure is effective for studying heat stress?

Research shows that prolonged exposure to hot indoor environments can harm health. Studies have found that overheating increases heart rate and workload, potentially leading to heat-related issues like heat stress or heat stroke. Reviews also indicate that excessive heat can cause discomfort and worsen existing health conditions. This trial will involve participants in a treatment arm experiencing daylong exposure to extreme heat, simulating indoor overheating conditions. Evidence suggests that understanding indoor heat exposure is crucial for preventing health problems, especially as extreme heat events become more common. ^{1 2 4 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 young adults aged 18-35 who speak English or French, do not smoke, and can give informed consent. It's designed to study the effects of heat waves on people in indoor settings without air conditioning.

Inclusion Criteria

I do not smoke.

I can understand and agree to the study's procedures and risks.

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

1-2 weeks

Exposure

Participants are exposed to high indoor temperatures in an environmental chamber for three successive days and two nights, with specific daytime and nighttime temperature settings.

3 days

Continuous exposure in the chamber

Assessment

Participants undergo cardiovascular, cognitive, and postural assessments during the exposure period.

3 days

Assessments conducted twice daily

Follow-up

Participants are monitored for any delayed physiological effects after the exposure period.

1 week

What Are the Treatments Tested in This Trial?

Interventions

• Simulated indoor overheating exposure

Trial Overview Participants will be exposed to high temperatures inside an environmental chamber simulating a heat wave. They'll experience daytime temps of 36°C and nighttime temps of 31°C over three days while their physiological responses are monitored.

How Is the Trial Designed?

Group I: Daylong exposure to extreme heat Experimental Treatment 1 Intervention

Young adults exposed to daylong indoor overheating associated with an extreme heat event involving a 10-hour daytime exposure at 36°C (45% relative humidity) followed by a 14-hour nighttime exposure at 31°C (45% relative humidity) over three successive days with only a daytime exposure on the final day.

Simulated indoor overheating exposure is already approved in European Union, United States for the following indications:

Approved in European Union as Lynparza for:

• Breast cancer
• Ovarian cancer
• Fallopian tube cancer
• Peritoneal cancer
• Pancreatic cancer
• Prostate cancer

Approved in United States as Lynparza for:

• Ovarian, fallopian tube, and primary peritoneal cancer
• Breast cancer
• Prostate cancer
• Pancreatic cancer

Who Is Running the Clinical Trial?

University of Ottawa

Lead Sponsor

Trials

231

Recruited

267,000+

Published Research Related to This Trial

A study of 31,642 heat stress illness cases among active duty servicemembers from 1998 to 2019 found that higher daily heat indices, particularly maximum wet bulb globe temperature (WBGT) and heat index, significantly increase the risk of heat-related illnesses, with risks nearly doubling at higher temperatures.

The research suggests that prevention strategies should consider previous day's heat levels and monitor various heat indices, not just WBGT, to better assess risks and implement effective control measures for heat stress illnesses.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Heat stress morbidity among US military personnel: Daily exposure and lagged response (1998-2019). Lewandowski, SA., Shaman, JL.[2022]

In a study involving 252 laboratory rats, it was found that running to exhaustion at various temperatures led to a higher risk of mortality from hyperthermia compared to being restrained and heated, with LD25 values of 16.8 and 30.1 degree-minutes, respectively.

The research indicates that both the severity of core heating and the physical effort involved can predict mortality rates, suggesting that exercise increases the risk of heatstroke even at lower temperatures.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Rat model of acute heatstroke mortality. Hubbard, RW., Bowers, WD., Matthew, WT., et al.[2017]

The study found that heat stress occupational exposure limits (OELs) based on wet bulb globe temperature (WBGT) are highly sensitive, with 88% to 97% of reported heat-related incidents exceeding these limits, indicating their effectiveness in preventing heat-related illnesses.

A Heat Index threshold of 80°F (26.7°C) was associated with 100% of fatalities and 99% of non-fatal heat-related incidents, suggesting it could serve as a useful alert for hazardous heat conditions when WBGT data is not available.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Actual and simulated weather data to evaluate wet bulb globe temperature and heat index as alerts for occupational heat-related illness. Morris, CE., Gonzales, RG., Hodgson, MJ., et al.[2020]

The PSU HEAT protocol shows excellent reliability and validity for determining critical environmental limits, with a high intraclass correlation coefficient (ICC) of 0.98 for between-visit reliability among 12 subjects.

The protocol effectively identifies critical temperature and humidity thresholds for heat stress, with strong agreement in results across different trials, indicating it can be reliably used to assess human heat balance.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Validity and reliability of a protocol to establish human critical environmental limits (PSU HEAT Project). Cottle, RM., Wolf, ST., Lichter, ZS., et al.[2023]

A study involving 64 residents in Phoenix, Arizona, developed five metrics to measure personal heat exposure, revealing that time spent outside and income were the strongest social risk factors associated with heat exposure.

The analysis indicated that the Mean Individually Experienced Temperature (IET) is a useful measure for assessing heat exposure differences, but it may not be optimal, as individual IETs often poorly correlated with regional weather data, highlighting the need for more personalized assessments.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Novel metrics for relating personal heat exposure to social risk factors and outdoor ambient temperature. Hondula, DM., Kuras, ER., Betzel, S., et al.[2021]

Citations

1. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC11346563/

Indoor overheating: A review of vulnerabilities, causes, and ... Data represents physiological responses measured in older adults (n = 39; 61–78 years; 11 females) during a daylong (9-hour) exposure to indoor overheating (40° ...

2. sciencedirect.com sciencedirect.com/science/article/pii/S2405844024018322

Review article Surviving indoor heat stress in United States ... The review illuminates the effects of overheating on thermal comfort, health, and socio-economic aspects within the built environment.

3. withpower.com withpower.com/trial/phase-sprains-and-strains-8-2024-b334d

Simulated Heat Exposure for Heat Stress ... Simulated indoor overheating exposure will have tolerable side effects & efficacy for patients with COVID-19 Stress Syndrome, Hamstring Strain, Heat Stress ...

4. ehp.niehs.nih.gov ehp.niehs.nih.gov/doi/full/10.1289/EHP13159

Effects of Daylong Exposure to Indoor Overheating on ... We evaluated surrogate physiological outcomes linked with heat-related mortality and morbidity in older adults during simulated indoor overheating.

5. nature.com nature.com/articles/s41467-025-57868-6

Meta-analysis of heat-induced changes in cardiac function ... Multilevel mixed-effects meta-analyses revealed exacerbated elevations in heart rate, cardiac output, and rate pressure product (estimate of cardiac workload)

6. thelancet.com thelancet.com/journals/lancet/article/PIIS0140-6736(21)01208-3/fulltext

Hot weather and heat extremes: health risks Hot ambient conditions and associated heat stress can increase mortality and morbidity, as well as increase adverse pregnancy outcomes and ...

7. federalregister.gov federalregister.gov/documents/2024/08/30/2024-14824/heat-injury-and-illness-prevention-in-outdoor-and-indoor-work-settings

Heat Injury and Illness Prevention in Outdoor and Indoor ... Excessive heat in the workplace can cause a number of adverse health effects, including heat stroke and even death, if not treated properly. Yet ...