Fan Vs. Heatwave

Benefits of fans in heatwaves cannot be determined based on the available evidence

(RxWiki News) It's been in the triple digits for days and your A/C goes out. So rush out and buy a half dozen box fans, right? Well….maybe. The experts just don't know.

A recent review of studies across the world found that there simply isn't enough evidence to know whether fans can help in a heatwave where the temperature reaches into the upper 90s and above.

With a temperature below 95 degrees Fahrenheit (35 degrees Celsius), a fan should help cool off a room. But once the temperature climbs above 95, the fan might actually be counterproductive and increase the heat in the room.

"Drink lots of water and lower activity level during a heatwave."

In a study led by Dr. Saurabh Gupta, a public health consultant at Hertfordshire Community NHS Trust in the United Kingdom, researchers reviewed the evidence on whether electric fans help or hurt during a heatwave.

They hoped to find out if, when temperatures are very high, fans tend to speed up heat loss or slow it down, so that recommendations could be made for heatwaves.

“It is important to know about the potential benefits and harms of electric fans when choosing whether to use one," Dr. Gupta said. "This is true if you are simply making a decision about your own use of a fan, but it also applies to broader public health decisions, such as whether to give electric fans to groups of people during a heatwave."

The researchers looked for both published and unpublished studies in any language in six different large databases of research, including MEDLINE and databases in India and China. Anything published up until April 2012 was considered.

They only looked for studies that were randomized trials or otherwise involved an experiment with electric fans, which could be ceiling fans, hand-held fans, portable fans or window fans.

However, they were unable to find any studies that were trials or experimental and which provided data about mortality rates, hospital admissions or other contacts with health care.

Even after consulting various experts who specialized in this kind of research, the only kinds of studies they were able to find were observational, retrospective studies, which means no experiment was conducted and there was no control group.

These kinds of studies can find links and associations between things, such as using a fan and hospital admissions, but they cannot establish that one thing caused another, so they are limited.

The observational studies the researchers did look at had mixed results. Some of the studies found a positive link between better health outcomes and use of an electric fan, but others found the opposite.

"Some suggested that fans might reduce health problems, while others suggested that the fans might make things worse," Dr. Gupta said.

Ultimately, the researchers had to conclude that the data did not provide enough information to know one way or the other whether electric fans are a good idea at very high temperatures.

"The evidence we identified does not resolve uncertainties about the health effects of electric fans during heatwaves," the authors wrote. "Therefore, this review does not support or refute the use of electric fans during a heatwave."

They suggested that people wanting to know whether they should use a fan or not may want to see what local policies recommend.

"The main implication of this review is that high quality research is needed to resolve the long standing and ongoing uncertainty about the benefits and harms of using electric fans during a heatwave," they concluded.

People making decisions about electric fans should consider the current state of the evidence base, and they might also wish to make themselves aware of local policy or guidelines when making a choice about whether or not to use or supply electric fans.

The study was published July 11 in The Cochrane Library. Information regarding funding and disclosures was unavailable.

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Review Date: 
July 12, 2012