Efficacy of Electric Fans for Mitigating Thermal Strain in Older Adults During Heat Waves
Condition: Hyperthermia; Weather; Heat; Heat Stress; Aging
MeSH terms: Hyperthermia
Study type: Interventional

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.
    


Intervention name(s): No cooling (control); Electric fan (low airflow); Electric fan (high airflow)
Intervention type(s): Other; Other; Other
Intervention description(s): 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.; 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.; 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.
Allocation: Randomized
Intervention model: Crossover Assignment
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.
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Basic Science
Keywords: Heat wave; Cooling intervention; Electric fans; Cardiovascular strain; Extreme heat events