How indoor humidity affects older adults' bodies during a heat wave

Is an Adjustment in the Recommended Indoor Temperature Upper Limit of 26°C Required During Higher Levels of Humidity?

This trial will test whether higher indoor humidity makes heat harder on older adults, including some with controlled high blood pressure or long-standing type 2 diabetes.

Quick facts

• Phase: NA
• Study type: Interventional
• Enrollment: 10 (estimated)
• Ages: 60 Years to 85 Years
• Sex: All
• Sponsor: University of Ottawa (other)
• Locations: 1 site (Ottawa, Ontario)
• Trial ID: NCT06842953 on ClinicalTrials.gov

What this trial studies

Participants will undergo controlled, laboratory-based simulated indoor overheating with varied humidity levels while researchers monitor physiological responses such as core temperature, heart rate, and cardiovascular strain. The protocol enrolls non-smoking older adults who can consent and speak English or French, and includes people with controlled hypertension or type 2 diabetes diagnosed at least five years prior. Individuals with uncontrolled hypertension, serious diabetes complications, recent severe hypoglycemia, or major activity-limiting conditions are excluded. Results aim to clarify how indoor humidity alters thermoregulation and cardiovascular burden in a vulnerable older population.

Who should consider this trial

Good fit: Ideal candidates are non-smoking older adults who can consent and speak English or French, including those with controlled chronic hypertension or type 2 diabetes diagnosed at least five years ago.

Not a fit: People with uncontrolled hypertension, serious diabetes complications, recent severe hypoglycemia, or significant physical impairments are excluded and therefore would not benefit directly from participation or have results applicable to them.

Why it matters

Potential benefit: If successful, the results could inform indoor humidity guidelines and help protect older adults during heat waves by identifying humidity conditions that increase physiological risk.

How similar studies have performed: Previous laboratory studies in younger and older adults have shown that high humidity worsens heat strain by reducing sweat evaporation, but the specific impact of indoor humidity on vulnerable older adults has not been directly tested.

Eligibility criteria

Inclusion Criteria:

* Non-smoking.
* English or French speaking.
* Ability to provide informed consent.
* with or without a) chronic hypertension (elevated resting blood pressure; as defined by Heart and Stroke Canada and Hypertension Canada), b) type 2 diabetes as defined by Diabetes Canada, with at least 5 years having elapsed since time of diagnosis

Exclusion Criteria:

* Episode(s) of severe hypoglycemia (requiring the assistance of another person) within the previous year, or inability to sense hypoglycemia (hypoglycemia unawareness).
* Serious complications related to diabetes (gastroparesis, renal disease, uncontrolled hypertension, severe autonomic neuropathy).
* Uncontrolled hypertension - BP \>150 mmHg systolic or \>95 mmHg diastolic in a sitting position.
* Restrictions in physical activity due to disease (e.g. intermittent claudication, renal impairment, active proliferative retinopathy, unstable cardiac or pulmonary disease, disabling stroke, severe arthritis, etc.).
* Use of or changes in medication judged by the patient or investigators to make participation in this study inadvisable.
* Cardiac abnormalities identified during screening

Where this trial is running

Ottawa, Ontario

• University of Ottawa — Ottawa, Ontario, Canada (RECRUITING)

Study contacts

• Study coordinator: Glen P Kenny, PhD

Conditions: Heat Stress, Physiological Stress, Heat wave, Indoor overheating, Thermoregulation, Heat strain, Elderly, Heat vulnerability