A newly published study from Australia has revealed that using fans incorrectly may increase the risk of heart attack.
According to The Sun, scientists from the University of Sydney recruited 20 participants to examine the effects of fan use on body temperature, heart rate, sweating, and comfort levels in hot and humid environments.
The research team also wanted to determine whether dehydration played a role. Participants underwent testing inside a climate-controlled chamber set at 39.2°C with 49% humidity.
In the first two trials, they were adequately hydrated, having consumed the recommended fluid intake in the 24 hours prior and being allowed to drink water throughout the test.
In the remaining two sessions, however, participants were dehydrated (having avoided water and high-water-content foods for 24 hours beforehand) and were not allowed to drink any fluids during the trials.
Each condition (hydrated and dehydrated) was tested under two scenarios: with a fan and without a fan. A series of indicators were measured, including heart rate, rectal temperature, whole-body sweat rate, heat discomfort, and thirst sensation.
The results showed that using a fan while dehydrated could increase strain on the heart—something that, over time, may raise the risk of heart attack. Experts concluded that fan use during dehydration increases sweat loss by about 60%. This means that if the body is already dehydrated, using a fan may do more harm than good.
Dr. Connor Graham, the lead researcher, explained: “Most people who die from extreme heat do not have air conditioning but often do own electric fans. Using a fan can help reduce heat stress and cardiovascular strain at temperatures up to 39–40°C. However, in hotter conditions, fans should be turned off as they may worsen heat stress.”
Dr. Graham noted that the reason lies in the high air temperature, which causes the body to heat up faster than it can cool itself through sweating. Previous studies also found that fan use could reduce heat and cardiovascular strain at temperatures up to about 39°C, but once the temperature exceeds 40°C, it is better to switch the fan off.
Earlier research also recommended that fans should only be used at temperatures below 39°C for healthy adults under 40, and below 38°C for older adults aged 65 and above. They also warned that fans should only be used at temperatures above 37°C for elderly individuals taking anticholinergic medications, such as oxybutynin, for bladder control.