Using a Fan Can Make Older Adults Hotter in a Dry Heat
upstart writes:
Using a fan can make older adults hotter in a dry heat:
Montreal Heart Institute-led research has found that older adults using an electric fan at 38 C and 60% relative humidity experienced a modest fall in core temperature and greater comfort. Fan use at 45 C and 15% relative humidity raised core temperature and increased discomfort.
CDC guidance warns against fan use above 32 C because of concerns that added airflow could speed heat gain in vulnerable groups. Modeling studies and small laboratory trials have hinted that airflow may help when humidity is high, but effects at very high temperatures in older adults have remained uncertain. Older individuals face elevated heat-related morbidity, creating an urgent need for practical, low-cost cooling ideas.
In the study, "Thermal and Perceptual Responses of Older Adults With Fan Use in Heat Extremes," published in JAMA Network Open, researchers performed a secondary analysis of a randomized crossover clinical trial to test how fan use and skin wetting influence core temperature, sweating, and thermal perception during extreme-heat exposures.
[...] In the humid chamber, fan use lowered rectal temperature by -0.1 C, raised sweat rate by 57 mL/h, and improved thermal sensation by -0.6 AU (arbitrary units using an ASHRAE 7-point scale) and comfort by -0.6 AU. Skin wetting cut sweat loss by 67 mL/h and eased perceptions, and combining both strategies produced the largest perceptual gains: thermal sensation -1.1 AU, comfort -0.7 AU, without altering core temperature.
In the dry chamber, fan use raised core temperature by 0.3 C, boosted sweating by 270 mL/h, and worsened sensation and comfort by 0.5 AU each. Skin wetting alone lowered sweating by 121 mL/h and improved sensation by -0.4 AU, with comfort unchanged.
Study investigators conclude that electric fans can serve as a safe, low-cost cooling option for older adults during hot, humid weather at 38 C, but should be avoided in very hot, dry conditions. Simple skin wetting offers an additional means to manage heat stress while limiting dehydration. Public health agencies may use these findings to refine summer heat-safety messages for seniors.
Journal Reference: Georgia K. Chaseling et al, Thermal and Perceptual Responses of Older Adults With Fan Use in Heat Extremes, JAMA Network Open (2025). DOI: 10.1001/jamanetworkopen.2025.23810
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