Heart rate, core body temperature rose more with electric fan use than without in 108 degree heat
WEDNESDAY, Sept. 7, 2016 (HealthDay News) — When the temperature rises to 108 degrees Fahrenheit or higher, older adults should not use an electric fan, according to a research letter published in the Sept. 6 issue of the Journal of the American Medical Association.
A total of three men and six women, average age 68, volunteered for the investigation. The participants sat in a room where the temperature was kept at nearly 108 degrees Fahrenheit for 100 minutes. The researchers kept the relative humidity at 30 percent for the first 30 minutes and then increased it by 2 percent every five minutes to a maximum humidity of 70 percent. On randomly assigned days, the volunteers sat in these heated rooms either with a 16-inch fan blowing on them from about three feet away or without the fan.
The study authors noted heart rates of up to nine beats per minute higher when using the fan. In addition, internal body temperatures were three-tenths to four-tenths of a degree higher during the fan sessions. For example, at 50 percent humidity, the average core temperature was 98.3 degrees Fahrenheit without the fan but 98.7 with the fan. Heart rate was 79 without the fan versus 88 with the fan.
“In contrast to young adults, fan use did not modify the critical relative humidity for rapid elevations in heart rate and core temperature of elderly adults exposed to extreme heat and humidity. Rather, fan use resulted in greater heart rate and core temperature,” the authors write. “Although differences were small, their cumulative effect may become clinically important with fan use during more prolonged heat exposure. Fan use elevates sweat loss in young adults. This was not observed in elderly adults, suggesting that age-related impairments in sweating capacity possibly limit the effectiveness of electric fans.”
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