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

NCT ID: NCT06142890

Last Updated: 2025-02-20

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 20 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2023-12-05
• Study Completion Date: 2024-02-10

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 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

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 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.

Ceiling fan generating airflow

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

Group Type: EXPERIMENTAL

Cooling with ceiling fan

Intervention Type: 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.

Interventions

No cooling (control)

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.

Intervention Type: OTHER

Cooling with ceiling fan

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.

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

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Glen P Kenny, PhD

Role: PRINCIPAL_INVESTIGATOR

University of Ottawa

Locations

University of Ottawa

Ottawa, Ontario, Canada

Countries

Canada

References

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. 2025 Sep 27. doi: 10.1111/jgs.70109. Online ahead of print.

Reference Type: DERIVED

PMID: 41014079 (View on PubMed)

Other Identifiers

H-11-21-7575

Identifier Type: -

Identifier Source: org_study_id