Fans Can Make Older Adults Feel Hotter in Dry Heat

Research led by the Montreal Heart Institute discovered that elderly individuals who used an electric fan at 38 °C with 60% humidity had a slight decrease in body temperature and felt more comfortable. However, when temperatures reached 45 °C with only 15% humidity, using a fan caused an increase in core temperature and made people feel less comfortable.

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The CDC advises against using fans when temperatures exceed 32°C due to worries that extra air movement might increase heat absorption among sensitive populations. Computer simulations and limited lab experiments suggest that air circulation could be beneficial under humid conditions, yet the impact at extremely hot temperatures on elderly people remains unclear. Elderly individuals experience higher rates of health issues related to heat, highlighting a pressing demand for effective, inexpensive cooling solutions.

In the research titled "Thermal and Perceptual Reactions of Elderly Individuals Using Fans During Extreme Heat Conditions," published in JAMA Network Open Researchers conducted a follow-up analysis of a randomized crossover study to examine the effects of using fans and skin moisture on body temperature, sweat production, and heat sensation during exposure to extremely hot conditions.

A group of 58 older adults (average age 68, standard deviation 7), who lived independently in the community, participated in 320 controlled lab-based heat trials. Each individual spent three hours inside a climate-controlled room maintained at either 38 °C with 60% humidity or 45 °C with 15% humidity. Among them, 27 had been diagnosed with coronary artery disease.

During the humid trial, exposures involved four randomly assigned scenarios: control, fan only, skin moistening only, and the combination of fan with skin moistening, each spaced apart by a minimum of 72 hours.

In extremely hot and dry conditions at 45 °C and 15% humidity, individuals diagnosed with coronary artery disease could only participate in control and skin-moisture sessions. Researchers measured rectal temperature, body weight before and after to calculate sweat rate, subjective thermal perception using a seven-level scale, and overall comfort via a four-tier scale.

In the moist environment, fans reduced rectal temperature by −0.1 °C, increased sweating by 57 mL/h, and enhanced thermal feeling by −0.6 AU (using an arbitrary scale from ASHRAE with seven points) as well as comfort by −0.6 AU. Increasing skin moisture decreased sweat output by 67 mL/h and made sensations more manageable. When both methods were combined, they provided the greatest improvements in perception: thermal feeling dropped by −1.1 AU, comfort improved by −0.7 AU, yet did not affect core body temperature.

In the dry environment, fan usage increased core body temperature by 0.3 °C, enhanced sweat production by 270 mL per hour, and reduced both feeling and comfort by 0.5 arbitrary units each. Alone, skin moisture decreased sweat output by 121 mL per hour and improved feelings by -0.4 arbitrary units, while comfort remained constant.

Research experts suggest that electric fans provide a secure, affordable way to cool down elderly individuals during warm, moist weather reaching 38°C, yet they should not be used in extremely hot, arid environments. Applying water to the skin can offer further relief from heat strain without increasing the risk of dehydration. Health organizations could apply these insights to improve advice about staying safe in high temperatures for senior citizens.

Created specifically for you by our writer Justin Jackson ,edited by Sadie Harley and verified and examined by Robert Egan —This article was created through diligent human effort. We depend on readers such as you to maintain independent scientific journalism. If this coverage is important to you, please think about a donation (especially monthly).

More information: Georgia K. Chaseling et al., Thermal and Perceived Reactions of Elderly Individuals Using Fans During Extreme Heat Conditions, JAMA Network Open (2025). DOI: 10.1001/jamanetworkopen.2025.23810

This narrative first appeared on Medical Xpress .