Suitability of the 26 °C Indoor Temperature Upper Limit for Older Adults: Impacts of Clothing and Daily Activity

NCT ID: NCT07189507

Last Updated: 2025-11-28

Basic Information

• Recruitment Status: RECRUITING
• Clinical Phase: NA
• Total Enrollment: 10 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2025-09-23
• Study Completion Date: 2027-03-31

Brief Summary

While an upper limit of 26°C has been shown to be protective for heat-vulnerable older occupants (DOI: 10.1289/EHP11651), this recommendation did not consider the added heat burden associated with increases in internal heat production accompanying activities of daily living or the restriction to heat loss caused by clothing insulation. To safeguard the health of older adults, health agencies worldwide recommend the remain in cool space indoors, avoid strenuous activity, wear lightweight clothing, and drink cool water regularly throughout the day. However, older adults do not sense heat as well as their younger counterparts. Consequently, they may not take appropriate countermeasures to mitigate physiological strain from indoor overheating. This may include overdressing despite high indoor temperatures. In other cases, individuals may wear insulated clothing in hot weather to observe cultural or religious modesty requirements, which serve as expressions of faith and identity rather than a tool for thermoregulation. Further, individuals may be unaware of the consequences of increases in physical activity on heat gain and may therefore not adjust their normal day-to-day activity levels to prevent potentially dangerous rises in body temperature. Consequently, this may necessitate a lowering of recommended upper indoor temperature limit during hot weather.

To address these important considerations, on separate occasions the investigators will assess the change in body temperature and cardiovascular strain in older adults (65-85 years) exposed for 8 hours to the recommended indoor temperature upper limit of 26°C and 45% relative humidity equivalent humidex of 29 (considered comfortable) while they A) perform seated rest dressed in light clothing (t-shirt, shorts and socks), B) perform light exercise (stepping exercise to simulate activities of daily living, 4-4.5 METS) every hour (except during lunch hour period) dressed in light clothing, C) perform light exercise (4-4.5 METS) every hour (except during lunch hour period) dressed in light clothing (t-shirt, shorts and socks) and an added clothing layer (sweatshirt and sweatpants) and D) perform seated rest dressed in light clothing (t-shirt, shorts and socks) and an added clothing layer (sweatshirt and sweatpants). With this experimental design, investigators will assess the effects of added clothing insulation and light activity, representative in activities of daily living on physiological strain and identify whether refinements in the recommended 26°C indoor temperature limit may be required.

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 upper limit without physical activity and added clothing.

Participants, dressed in light clothing (t-shirt, shorts and socks), perform seated rest while exposed daylong (8 hours) to an indoor temperature maintained at 26°C and 45% relative humidity (humidex equivalent of 29).

Group Type: EXPERIMENTAL

Simulated indoor temperature upper limit

Intervention Type: OTHER

Older adults exposed to an 8-hour simulated exposure.

Exposure to indoor temperature upper limit with physical activity.

Participants, dressed in light clothing (t-shirt, shorts and socks), perform light exercise (i.e., stepping, representing activities of daily living, 4-4.5 METS) every hour (except during lunch hour period) while exposed daylong (8 hours) to an indoor temperature maintained at 26°C and 45% relative humidity (humidex equivalent of 29).

Group Type: EXPERIMENTAL

Simulated indoor temperature upper limit

Intervention Type: OTHER

Older adults exposed to an 8-hour simulated exposure.

Exposure to indoor temperature upper limit with added clothing.

Participants, dressed in light clothing (t-shirt, shorts and socks) and an added clothing layer (sweatshirt and sweatpants), perform seated rest while exposed daylong (8 hours) to an indoor temperature maintained at 26°C and 45% relative humidity (humidex equivalent of 29).

Group Type: EXPERIMENTAL

Simulated indoor temperature upper limit

Intervention Type: OTHER

Older adults exposed to an 8-hour simulated exposure.

Exposure to indoor temperature upper limit with physical activity and added clothing.

Participants, dressed in light clothing (t-shirt, shorts and socks) and an added clothing layer (sweat shirt and sweat pants), perform light exercise (i.e., stepping, representing activities of daily living, 4-4.5 METS) every hour (except during lunch hour period) while exposed daylong (8 hours) to an indoor temperature maintained at 26°C and 45% relative humidity (humidex equivalent of 29).

Group Type: EXPERIMENTAL

Simulated indoor temperature upper limit

Intervention Type: OTHER

Older adults exposed to an 8-hour simulated exposure.

Interventions

Simulated indoor temperature upper limit

Older adults exposed to an 8-hour simulated 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

Full Professor, University Research Chair

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Glen Kenny, PhD

Role: PRINCIPAL_INVESTIGATOR

University of Ottawa

Locations

University of Ottawa

Ottawa, Ontario, Canada

Site Status: RECRUITING

Countries

Canada

Central Contacts

Glen P Kenny, PhD

Role: CONTACT

gkenny@uottawa.ca

6135625800 ext. 4282

Facility Contacts

Glen P Kenny, PhD

Role: primary

gkenny@uottawa.ca

6135625800 ext. 4282

Other Identifiers

HEPRU-2025-09-A

Identifier Type: -

Identifier Source: org_study_id