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

NCT ID: NCT05695079

Last Updated: 2023-06-18

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 19 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2022-12-01
• Study Completion Date: 2023-04-10

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

Study Design

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

Study Groups

No cooling intervention (control)

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

Group Type: ACTIVE_COMPARATOR

No cooling (control)

Intervention Type: 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.

Fan generating low airflow

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

Group Type: EXPERIMENTAL

Electric fan (low airflow)

Intervention Type: 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 high airflow

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

Group Type: EXPERIMENTAL

Electric fan (high airflow)

Intervention Type: 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.

Interventions

No cooling (control)

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.

Intervention Type: OTHER

Electric fan (low airflow)

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.

Intervention Type: OTHER

Electric fan (high airflow)

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.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

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

Exclusion Criteria

• 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).

• 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 P Kenny, PhD

Role: PRINCIPAL_INVESTIGATOR

University of Ottawa

Ronald J Sigal, MD, MPH

Role: PRINCIPAL_INVESTIGATOR

University of Calgary

Locations

University of Ottawa

Ottawa, Ontario, Canada

Countries

Canada

References

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.

Reference Type: DERIVED

PMID: 40542541 (View on PubMed)

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.

Reference Type: DERIVED

PMID: 40020224 (View on PubMed)

Other Identifiers

H-11-21-7572

Identifier Type: -

Identifier Source: org_study_id