Efficacy of Electric Fans for Mitigating Thermal Strain in Older Adults During Heat Waves

NCT05695079 | Completed

• 1 other identifier: H-11-21-7572
• Study Type: interventional
• Target: 19
• 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 increasing green house gas emissions. For these reasons, recent guidance has advocated the use of electric fans as a simple and sustainable alternative to air-conditioning. To date, however, only one study has assessed the efficacy of fan use in older adults and demonstrated that fans accelerate increases in body temperature and heart rate in a short-duration (\~2 hours) resting exposure to 42°C with increasing ambient humidity from 30-70%. While subsequent modelling has suggested that fans can improve heat loss via sweat evaporation in healthy older adults at air temperatures up to 38°C, there is currently no empirical data to support these claims. Further, that work assumed older adults were seated in front of a pedestal fan generating an airflow of 3·5-4·5 m/s at the front of the body. This airflow cannot be attained by most marketed pedestal fans. Studies are therefore needed to evaluate the efficacy of fans for preventing hyperthermia and the associated physiological burden in older adults in air temperatures below 38°C and determine whether the cooling effect of fans, if any, is evident at lower rates of airflow. To address these knowledge gaps, this randomized crossover trial will evaluate body core temperature, cardiovascular strain, dehydration, and thermal comfort in adults aged 65-85 years exposed for 8 hours to conditions experienced during hot weather and heat waves in North America simulated using a climate chamber (36°C, 45% relative humidity). Each participant will complete three randomized exposures that will differ only in the airflow generated at the front of the body via an electric pedestal fan: no airflow (control), low airflow (\~2 m/s), and high airflow (\~4 m/s). While participants will spend most of the 8-hour exposure seated in front of the fan, they will also complete 4 x 10 min periods of 'activities of daily living' (\~2-2.5 METS, light stepping) at \~2 hour intervals to more accurately reflect activity patterns in the home.

Conditions

Hyperthermia; Weather; Heat; Heat Stress; Aging

Keywords

Heat wave; Cooling intervention; Electric fans; Cardiovascular strain; Extreme heat events

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 (15)

• 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 (AUC)

  End of heat exposure (hour 8)

• Heart rate (end-exposure)

  End of heat exposure (hour 8)

Study Arms (3)

No cooling intervention (control)

ACTIVE COMPARATOR

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

Other: No cooling (control)

Fan generating low airflow

EXPERIMENTAL

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

Other: Electric fan (low airflow)

Fan generating high airflow

EXPERIMENTAL

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

Other: Electric fan (high airflow)

Interventions

No cooling (control) OTHER

Participants are exposed to 36°C, 45% relative humidity for 8 hours without cooling intervention (control condition). Drinking water is available ad libitum. Participants are seated throughout exposure, except for during 10 min periods of simulated activities of daily living (light stepping at 2-2.5 METS) performed at hours 1, 3, 5, and 7.

No cooling intervention (control)

Electric fan (low airflow) OTHER

Participants are exposed to 36°C, 45% relative humidity for 8 hours without cooling interventions (control condition). Drinking water is available ad libitum. Participants are seated throughout exposure, except for during 10 min periods of simulated activities of daily living (light stepping at 2-2.5 METS) performed at hours 1, 3, 5, and 7. While participants are seated, an electric pedestal fan positioned 1 m away will deliver a continuous airflow of 2 m/s to the front of the body.

Fan generating low airflow

Electric fan (high airflow) OTHER

Participants are exposed to 36°C, 45% relative humidity for 8 hours without cooling interventions (control condition). Drinking water is available ad libitum. Participants are seated throughout exposure, except for during 10 min periods of simulated activities of daily living (light stepping at 2-2.5 METS) performed at hours 1, 3, 5, and 7. While participants are seated, an electric pedestal fan positioned 1 m away will deliver a continuous airflow of 4 m/s to the front of the body.

Fan generating high 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 (3)

• King K, McCormick J, O'Connor F, Meade R, Kenny G. The efficacy of fan use on autophagy and the cellular stress response during prolonged exposure to extreme heat in older adults: a randomized trial. Appl Physiol Nutr Metab. 2026 Jan 1;51:1-11. doi: 10.1139/apnm-2025-0250.

  PMID: 41297035 DERIVED

• Lee BJ, McCarthy T, O'Connor F, Davey SL, Thake CD, McCormick JJ, King KE, Boulay P, Meade RD, Kenny GP. Effect of pedestal fan use on serum stress biomarkers in older adults exposed to simulated daylong indoor overheating. Physiol Rep. 2025 Jun;13(12):e70390. doi: 10.14814/phy2.70390.

  PMID: 40542541 DERIVED

• O'Connor F, McGarr G, Harris-Mostert R, Boulay P, Sigal R, Meade R, Kenny GP. Effects of pedestal-mounted electric fans on self-reported symptoms and mood-state in older adults exposed to indoor overheating during a simulated heatwave: an exploratory analysis. Appl Physiol Nutr Metab. 2025 Jan 1;50:1-12. doi: 10.1139/apnm-2024-0461.

  PMID: 40020224 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

• Ronald J Sigal, MD, MPH

  University of Calgary

  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). Data will be blinded prior to analysis.
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Full Professor, University Research Chair

Model Details: Each participant will complete 3 simulated heat wave exposures in random order: i) no electric fan (control); ii) electric fan generating air flow of 2 m/s at the front of the body; and iii) electric fan generating air flow of 4 m/s at the front of the body.

Study Record Dates

• First Submitted: January 12, 2023
• First Posted: January 23, 2023
• Study Start: December 1, 2022
• Primary Completion: April 10, 2023
• Study Completion: April 10, 2023
• Last Updated: June 18, 2023

Record last verified: 2023-06

Data Sharing

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

Locations

CA (1)