In the waning days of summer, residents who turn to electric fans to find relief from high heat and humidity may be doing themselves more harm than good, according to the findings of a new study published in JAMA, the journal of the American Medical Association.

Heart specialists at University of Texas Southwestern Medical Center were surprised when their research found that the heart rate and internal temperature of older adults exposed to 107-degree F temperatures and increasing humidity levels climbed even higher — instead of falling as they expected — when they tried to cool off with fans.

“Although differences were small, the cumulative effect could become clinically important during prolonged heat exposure, such as during extreme heat waves,” said Craig Crandall, Ph.D., a professor of internal medicine at UT Southwestern.

Whereas electric fans keep younger adults cooler by helping to evaporate their sweat, older adults’ capacity to sweat may be impaired, so fans not only do not cool them on exceptionally hot days, but they may increase “thermal and cardiac strain,” Crandall added.

During severe heat waves, older adults who do not live in air-conditioned settings should stay hydrated and seek an air-conditioned environment such as the home of a family member or friend, a community center or a shopping mall, Crandall said.

The details

The small study included eight adults aged 60 to 90 years. Crandall and coauthors observed them for approximately two hours in a room where the temperature was set at 107 degrees F and the humidity level gradually was increased from 30% to 70%. The researchers were not surprised that the older adults’ heart rates and internal body temperature increased with the humidity level in the room.

The study participants were tested with and without an electric fan. Their heart rates were 10 beats per minute higher and their internal temperatures 0.5 degrees F higher when a fan was part of the experiment.

Although these findings suggest that fan use may be counterproductive for older adults during heat waves, the researchers propose that fan use still may be beneficial under less extreme environmental conditions, although they said that this idea needs to be confirmed.