(RxWiki News) An electric fan sounds good during the dog days of summer, but some public health organizations have advised against the use of fans in severe heat because they might increase body heating. New evidence suggests, however, that this advice may be misguided.
A new study may refute these past claims that fans can be harmful in high heat — at least in healthy young men. The authors of this new study recommended further study of other populations like the elderly and suggested that fan use guidelines be re-evaluated.
“Our preliminary study is the first, to our knowledge, to demonstrate that electric fans prevent heat-related elevations in [heart rate] and core temperature in healthy young men up to approximately 80% [humidity] at [97 degrees Fahrenheit] and 50% humidity at [108 F]," the authors of this study wrote. "Thus, contrary to existing guidance, fans may be effective cooling devices for those without air conditioning during hot and humid periods.”
The human body cools itself by sweating, varying the rate and depth of blood circulation and — in severe heat — by panting. If the external temperature continues to rise, the body can overheat to the point of heatstroke.
As outside heat increases, small blood vessels near the skin dilate so heat can be released into the air. High external temperatures decrease the body's ability to cool itself because the heat moves from high to low temperature. A fan can cool the skin, which may mean the heat from the outside air moves into the body through the skin.
Water is released through the skin as perspiration. Fans can help evaporate the sweat. When the air is humid, however, sweat cannot evaporate as well.
Although high heat is of particular concern to elderly people, Sara Doss, MD, an adult internal medicine physician and assistant professor in the Department of Medicine at Loyola University Stricht School of Medicine, cautions against extending the results of this study to the elderly because it included only younger males. "This is likely because the method of completing the study was sort of extreme (108 degrees Fahrenheit for hours with a fan on them or off them)," she said.
"Also, elderly people tend to sweat less than a younger population, so the whole argument of sweating to help with core temp regulation is trickier in the elderly population," Dr. Doss said. "I am not sure I would use the study to make recommendations to the elderly population in times of extreme heat and humidity. I think, in general, I would recommend a cool, dry environment with air conditioning."
Lead study author Ollie Jay, PhD, of the University of Sydney at New South Wales, Australia, and colleagues looked at what happened if fans were used in high-heat and high-humidity environments. These researchers placed healthy young men in chambers with controlled temperature and humidity.
Dr. Jay and team kept one chamber at 97 F and one at 108 F. Each chamber was tested both with and without an 18-inch fan facing the subject from about three feet away. After the first 20 minutes, the humidity in each chamber was increased in 15 equal steps.
In the 97-degree chamber, the humidity gradually increased from 25 to 95 percent. In the 108-degree chamber, the humidity increased from 20 to 70 percent.
These researchers found that fans helped in both chambers. Fans helped the subjects keep cooler up to 80 percent humidity in the 97-degree chamber and up to 50 percent in the 108-degree chamber.
Dr. Jay and team wrote that, although their study only looked at young men, "Advice to the public to stop using fans during heat waves may need to be reevaluated." These researchers called for further study on this topic in other groups, such as the elderly.
This study was published Feb. 17 in JAMA.
The Natural Sciences and Engineering Research Council of Canada funded this research. Dr. Jay and team disclosed no conflicts of interest.