In a study appearing in the September 6 issue of JAMA, Craig G. Crandall, Ph.D., of the University of Texas Southwestern Medical Center, Dallas, and colleagues examined whether electric fan use would delay elevations in heart rate and core temperature of elderly adults exposed to extreme heat and humidity.
Research has indicated that electric fan use delays elevations in heart rate and core temperature of young adults exposed to 108°F. However, it remains unknown if fans are effective in vulnerable populations, such as the elderly who display altered cardiovascular and thermoregulatory responses during heat exposure. This study included 3 men and 6 women volunteers (average age, 68 years). Wearing shorts (men) or shorts and a sports bra (women), participants sat in a chamber maintained at 108°F. After 30 minutes at a relative humidity of 30 percent, relative humidity was increased 2 percent every 5 minutes to 70 percent (100 minutes total). On separate randomly assigned days, participants performed the protocol with or without a 16-in fan facing them from about 3 feet. No fluid intake was allowed during the protocol. Measurements taken included heart rate, core temperature and sweat loss.
The researchers found that fan use resulted in greater heart rate and core temperature. "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. Overall, this preliminary study indicates that electric fans may be detrimental for attenuating cardiovascular and thermal strain of elderly adults during heat waves."
(doi:10.1001/jama.2016.10550; the study is available pre-embargo to the media at the For the Media website)
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