Efficacy of Ceiling Fans for Mitigating Thermal Strain During Bed Rest in Older Adults During Heat Waves

NCT06142890 | Completed

• 1 other identifier: H-11-21-7575
• Study Type: interventional
• Target: 20
• Locations: 1 country
• Sites: 1

Brief Summary

With the increasing regularity and intensity of hot weather and heat waves, there is an urgent need to develop heat-alleviation strategies able to provide targeted protection for heat-vulnerable older adults. While air-conditioning provides the most effective protection from extreme heat, it is inaccessible for many individuals. Air-conditioning is also energy intensive, which can strain the electrical grid and, depending on the source of electricity generation, contribute to green house gas emissions. For these reasons, recent guidance has recommended the use of electric fans as a sustainable cooling alternative. While fans may increase sweat evaporation and heat loss in healthy, young adults, evidence supporting their use in older adults is scarce. Further, studies show that when environmental temperature exceeds skin temperature, fans are not effective and can even exacerbate hyperthermia in older adults. While older adults only account for \~13% of the population, they account for \~40% off all hospitalizations. In the context of sustainable cooling interventions, this is of particular importance given that many hospitals and long-term care homes do not have air-conditioning and rely on ceiling fans to enhance sweat evaporation while participants are bed-resting. While recent biophysical modelling has suggested that pedestal fans likely provide a clinically meaningful cooling effect (proposed to be ≥0.3°C) in temperatures below \~34°C in older adults, the efficacy of ceiling fans in mitigating heat strain in these conditions is currently unknown. To address these knowledge gaps, this randomized crossover trial will evaluate body core temperature, cardiovascular strain, orthostatic intolerance, dehydration, and thermal comfort in adults aged 65-85 years exposed for 8-hours to conditions experienced during indoor overheating occurring during a heat wave in a temperate continental climate (31°C, 45% relative humidity). Each participant will complete two randomized exposures that will differ only in the airflow generated by a ceiling fan: no airflow (control) or standard airflow. Participants will remain in a supine position for the duration of the 8-hour exposure period, except for during hour 7 when they will complete a series of cardiovascular autonomic response tests.

Conditions

Hyperthermia; Heat Stress; Cooling; Aging

Keywords

Heat wave; Cooling intervention; Elderly; Thermoregulation; Cardiovascular strain; Extreme heat event

Outcome Measures

Primary Outcomes (1)

• Core temperature (peak)

  Peak rectal temperature (15 min average) during exposure. Rectal temperature is measured continuously throughout each simulated heat wave.

  End of heat exposure (hour 8)

Secondary Outcomes (18)

• Core temperature (AUC)

  End of heat exposure (hour 8)

• Core temperature (end-exposure)

  End of heat exposure (hour 8)

• Heart rate (peak)

  End of heat exposure (hour 8)

• Heart rate (end-exposure)

  End of heat exposure (hour 8)

• Heart rate (AUC)

  End of heat exposure (hour 8)

Study Arms (2)

No cooling intervention (control)

ACTIVE COMPARATOR

Adults aged 65-85 years with or without type 2 diabetes and/or hypertension

Other: No cooling (control)

Ceiling fan generating airflow

EXPERIMENTAL

Adults aged 65-85 years with or without type 2 diabetes and/or hypertension

Other: Cooling with ceiling fan

Interventions

No cooling (control) OTHER

Participants are exposed to 31°C, 45% relative humidity for 8 hours without cooling intervention (control condition). Drinking water is available ad libitum. Participants remain in supine position with slight (\~20°) chest and head elevation (low-Fowlers position) throughout the duration of bed-rest exposure.

No cooling intervention (control)

Cooling with ceiling fan OTHER

Participants are exposed to 31°C, 45% relative humidity for 8 hours. Drinking water is available ad libitum. Participants remain in supine position with slight (\~20°) chest and head elevation (low-Fowlers position) throughout the duration of bed-rest exposure. Participants will remain under a commercially available ceiling fan generating a standard air flow throughout the duration of exposure.

Ceiling fan generating airflow

Eligibility Criteria

• Age: 65 Years - 85 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Older Adult (65+)

You may qualify if:

• Male or female adults.
• Aged 65-85 years.
• Non-smoking.
• English or French speaking.
• Ability to provide informed consent.

You may not qualify if:

• Physical restriction (e.g., due to disease: 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 (e.g., medications increasing risk of heat-related illness; beta blockers, anticholinergics, etc.)
• Cardiac abnormalities identified via 12-lead ECG during an incremental exercise test to volitional fatigue (performed for all participants).
• Peak aerobic capacity (VO2peak), as measured during an incremental exercise test to volitional fatigue, exceeding the 50th percentile of age- and sex-specific normative values published by the American College of Sports Medicine (ACSM).

Sponsors & Collaborators

• University of Ottawa: lead

Study Sites (1)

University of Ottawa

Ottawa, Ontario, K1N6N5, Canada

Location

Related Publications (1)

• O'Connor FK, Meade RD, Janetos KT, Li-Maloney C, Sigal RJ, Boulay P, Kenny GP. Effect of Ceiling Fans on Core Temperature in Bed-Resting Older Adults Exposed to Indoor Overheating. J Am Geriatr Soc. 2026 Jan;74(1):200-204. doi: 10.1111/jgs.70109. Epub 2025 Sep 27.

  PMID: 41014079 DERIVED

MeSH Terms

Conditions

Hyperthermia; Heat Stress Disorders

Condition Hierarchy (Ancestors)

Body Temperature Changes; Signs and Symptoms; Pathological Conditions, Signs and Symptoms; Wounds and Injuries

Study Officials

• Glen P Kenny, PhD

  University of Ottawa

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, OUTCOMES ASSESSOR
• Masking Details: Participants will be informed of the study interventions before providing informed consent but will be masked to the order of the arms until exposure (i.e., participants will not know the fan conditions before entering the environmental chamber). Data will be blinded prior to analysis (including during statistical analysis).
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Full Professor

Model Details: Each participant will complete 2 simulated heat wave exposures in random order: i) bed-rest; no fan cooling (control) and ii) bed-rest positioned beneath a ceiling fan providing standard air flow.

Study Record Dates

• First Submitted: November 13, 2023
• First Posted: November 22, 2023
• Study Start: December 5, 2023
• Primary Completion: February 10, 2024
• Study Completion: February 10, 2024
• Last Updated: February 20, 2025

Record last verified: 2025-02

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ANALYTIC CODE
• Time Frame: Following publication of the main report(s)
• Access Criteria: Approved analysis plan and signed access agreement

Locations

CA (1)