Clinical trial NCT05695079: Efficacy of Electric Fans for Mitigating Thermal Strain in Older Adults During Heat Waves
Official title: Evaluating the Efficacy of Pedestal Fans for Limiting Heat Strain in Elderly Adults During Extreme Heat Events
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Hyperthermia
Weather; Heat
Heat Stress
Aging
Keywords: Heat wave
Cooling intervention
Electric fans
Cardiovascular strain
Extreme heat events
Lead sponsor: University of Ottawa
Sponsor class: OTHER
First posted: 2023-01-23
Enrollment: 19
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 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.
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 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.


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 (AUC)
timeFrame: End of heat exposure (hour 8)
measure: Heart rate (end-exposure)
timeFrame: End of heat exposure (hour 8)
measure: Systolic blood pressure (end-exposure)
timeFrame: End of heat exposure (hour 8)
measure: Diastolic blood pressure (end-exposure)
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: End of heat exposure (hour 8)
measure: Heart rate variability: RMSSD (end-exposure)
timeFrame: End of heat exposure (hour 8)
measure: Fluid consumption
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: Air movement scale (end-exposure)
timeFrame: End of heat exposure (hour 8)
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
affiliation: University of Calgary
name: Ronald J Sigal, MD, MPH
role: PRINCIPAL_INVESTIGATOR
References: