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Influence of Indoor Humidity on Physiological Strain in Older Adults During a Simulated Heat Wave

NCT06842953 · Status: RECRUITING · Phase: NA · Type: INTERVENTIONAL · Enrollment: 10

Last updated 2025-06-15

No results posted yet for this study

Summary

Laboratory-based studies show that exposure to high humidity can worsen the effects of heat stress in young and older adults by impeding sweat evaporation - the main mechanism by which the human body cools itself. At high levels of humidity, the efficiency of sweating decreases causing a greater rise core temperature and burden on the cardiovascular system. In this context, increasing temperatures and humidity with climate change thus pose a potential compound risk for human health. While humidity's role in heat-health outcomes could substantially alter projections of health burdens from climate change, the impact of humidity on physiological strain in vulnerable people in relation to the indoor environment has yet to be evaluated. In a recent study delineating the physiological effects of the proposed 26°C indoor upper limit (PMID: 38329752), relative humidity was set to 45% in all conditions based on indoor humidity standards by the American Society of Heating and Air-Conditioning Engineers. However, it is unknown whether a refinement of the recommended indoor temperature limit of 26°C is required in situations where humidity cannot be maintained at this level.

On separate occasions, the investigators will assess the change in body temperature and cardiovascular strain in older adults (65-85 years) exposed for 10 hours at the recommended indoor temperature limit of 26°C and 45% relative humidity (equivalent humidex of 29 (considered comfortable)) (experimental condition A), to 26°C with a relative humidity of 15% (equivalent humidex of 23 (considered comfortable); humidex is used to measure the perceived temperature taking into account the humidity)) (experimental condition B), to 26°C with a relative humidity of 85% (equivalent humidex of 37 (considered somewhat uncomfortable)) (experimental condition C), and to 31°C and 45% relative humidity with an equivalent humidex of 37 (considered somewhat uncomfortable) that is similar to experimental condition C. With this experimental design, investigators will assess the effects of indoor humidity in driving human heat strain and identify whether refinements in the recommended 26°C indoor temperature limit may be required. Further, by evaluating changes in relation to ambient conditions with a similar humidex, the investigators can assess how individuals perceive and respond to both heat and humidity.

Conditions

  • Heat Stress
  • Physiological Stress

Interventions

OTHER

Simulated indoor overheating

Older adults are exposed to a 10-hour simulated exposure

Sponsors & Collaborators

  • University of Ottawa

    lead OTHER

Study Design

Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
Model
CROSSOVER

Eligibility

Min Age
60 Years
Max Age
85 Years
Sex
ALL
Healthy Volunteers
Yes

Timeline & Regulatory

Start
2025-03-14
Primary Completion
2026-03-31
Completion
2026-09-01

Countries

  • Canada

Study Locations

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Read the full study record

This page highlights key information. For complete eligibility criteria, study locations, investigator contacts, and the full protocol, visit the original record on ClinicalTrials.gov.

View NCT06842953 on ClinicalTrials.gov