Clinical trial NCT06142890: Efficacy of Ceiling Fans for Mitigating Thermal Strain During Bed Rest in Older Adults During Heat Waves
Official title: Evaluating the Efficacy of Ceiling Fans for Limiting Heat Strain in Elderly Adults During Bed Rest in an Extreme Heat Event
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Hyperthermia
Heat Stress
Cooling
Aging
Keywords: Heat wave
Cooling intervention
Elderly
Thermoregulation
Cardiovascular strain
Extreme heat event
Lead sponsor: University of Ottawa
Sponsor class: OTHER
First posted: 2023-11-22
Enrollment: 20
Sex: ALL
Minimum age (years): 65
Maximum age (years): 85
Standard ages: OLDER_ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Intervention model description: 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.
Primary purpose: BASIC_SCIENCE

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.


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).

Primary outcomes:
measure: Core temperature (peak)
timeFrame: End of heat exposure (hour 8)
Secondary outcomes:
measure: Core temperature (AUC)
timeFrame: End of heat exposure (hour 8)
measure: Core temperature (end-exposure)
timeFrame: End of heat exposure (hour 8)
measure: Heart rate (peak)
timeFrame: End of heat exposure (hour 8)
measure: Heart rate (end-exposure)
timeFrame: End of heat exposure (hour 8)
measure: Heart rate (AUC)
timeFrame: End of heat exposure (hour 8)
measure: Cardiac Response to Standing From Supine (30:15 Ratio)
timeFrame: During heat exposure (hour 7)
measure: Systolic Response to Standing From Supine
timeFrame: During heat exposure (hour 7)
measure: Systolic blood pressure
timeFrame: End of heat exposure (hour 8)
measure: Diastolic blood pressure
timeFrame: End of heat exposure (hour 8)
measure: Rate pressure product (end-exposure)
timeFrame: End of heat exposure (hour 8)
measure: Heart rate variability: SDNN (end-exposure)
timeFrame: During heat exposure (hour 7)
measure: Heart rate variability: RMSSD (end-exposure)
timeFrame: During heat exposure (hour 7)
measure: Fluid consumption
timeFrame: End of heat exposure (hour 8)
measure: Whole-body sweat rate
timeFrame: End of heat exposure (hour 8)
measure: Fluid loss
timeFrame: End of heat exposure (hour 8)
measure: Change in plasma volume
timeFrame: End of heat exposure (hour 8)
measure: Thermal comfort scale (end-exposure)
timeFrame: End of heat exposure (hour 8)
measure: Orthostatic intolerance symptoms assessment
timeFrame: During heat exposure (hour 7)
Other outcomes:
Locations:
city: Ottawa
country: Canada
facility: University of Ottawa
state: Ontario
Study officials:
affiliation: University of Ottawa
name: Glen P Kenny, PhD
role: PRINCIPAL_INVESTIGATOR
References: