Physiological Strain in Older Adults During a Simulated Heat Wave

NCT ID: NCT06633302

Last Updated: 2025-06-17

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 18 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2024-10-15
• Study Completion Date: 2025-05-21

Brief Summary

A recent report showed that maintaining indoor temperature at or below 26°C safeguards older, heat vulnerable adults against potentially dangerous increases in thermal and cardiovascular strain during an extreme heat event (PMID: 38329752). However, this proposed limit does not consider the potential cumulative effect of successive days of heat exposure, which could lead to a progressive deterioration in thermoregulatory and cardiovascular function and necessitate adjustments to upper indoor temperature limits. Further, thermal comfort and quality of sleep may be negatively impacted when bedroom temperatures exceed 24°C (PMID: 3090680). On this basis, some health agencies have recommended that bedroom temperatures at night should not exceed 26°C unless ceiling fans are available (PMID: 3090680). Currently, however, it is unknown whether indoor overheating impairs sleep quality and physiological strain on a subsequent day in older adults and, if so, whether maintaining indoor temperature at 26°C is sufficient to prevent these adverse health impacts.

With rising global temperatures and more extreme heat events, energy management strategies to limit the strain on the power grid during the daytime are now increasingly commonplace. Thus, understanding the benefits of maintaining indoor temperature at the recommend upper limits of 26°C during the nighttime only on surrogate physiological indicators of health is an important step in understanding how to optimize protection for heat-vulnerable older adults when power outages occur.

The investigators will assess the efficacy of proposed indoor temperature limits (i.e., 26°C) in mitigating increases in core temperature and cardiovascular strain over three consecutive days (3 days, 2 nights) in older adults (60-85 years) with (indoor temperatures maintained at the recommend 26°C at all times throughout the three days) and without (daytime temperature fixed at 34°C (temperature experienced in homes without air-conditioning during an extreme heat event) with nighttime temperature at 26°C) access to daytime cooling. By quantifying the effect of daylong indoor overheating on surrogate physiological outcomes linked with heat-related mortality and morbidity in older adults, the investigators can determine if refinements in the recommended upper temperature threshold is required, including best practices when power outages may occur during an extreme heat event.

Conditions

Heat Stress; Physiological Stress

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: SINGLE

Study Groups

Exposure to indoor temperature limits daylong

Participants exposed to three consecutive days (3 days, 2 nights) in an indoor environment maintained at either 26°C at all times (condition A, recommended upper indoor temperature limits during an extreme heat event).

Group Type: EXPERIMENTAL

Simulated multi-day heatwave exposure

Intervention Type: OTHER

Older adults exposed to a multi-day simulated heat wave exposure

Exposure to indoor temperature limits nighttime only

Participants exposed to three consecutive days (3 days, 2 nights) to indoor overheating during the daytime (34°C, temperatures experienced in homes without air-conditioning) (9:00 to 19:00) with nighttime (19:00 to 9:00) indoor temperatures reduced to the recommended limit of 26°C.

Group Type: EXPERIMENTAL

Simulated multi-day heatwave exposure

Intervention Type: OTHER

Older adults exposed to a multi-day simulated heat wave exposure

Interventions

Simulated multi-day heatwave exposure

Older adults exposed to a multi-day simulated heat wave exposure

Intervention Type: OTHER

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 your 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

• Minimum Eligible Age: 65 Years
• Maximum Eligible Age: 85 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

University of Ottawa

OTHER

Sponsor Role: lead

Responsible Party

Glen P. Kenny

Professor

Responsibility Role: PRINCIPAL_INVESTIGATOR

Locations

University of Ottawa

Ottawa, Ontario, Canada

Countries

Canada

Other Identifiers

HEPRU-2024-08-A

Identifier Type: -

Identifier Source: org_study_id