Fans may not keep the elderly cool during heat waves

Air blown from an electric fan alone is not enough to cool older adults who are suffocating indoors in a heat wave, a new study shows. A study of 18 adults aged 65 to 72, monitored in a climate-controlled room simulating extreme heat wave conditions, found little change in peak core temperatures as a result of electric fan use, scientists report on October 17 in Journal of the American Medical Association.

Older adults, many of whom prefer to weather heat waves in their homes, are particularly at risk for heat-related health impacts (SN: 14.5.24). In the absence of access to air conditioning, the use of pedestal-style electric fans has been a recommended strategy for individuals at home to try to stay cool. Fans can accelerate heat loss, lowering core body temperature, increasing sweat evaporation.

But recent studies based on biophysical models have suggested that fans may not provide much cooling as the ambient temperature reaches 33° Celsius (91° Fahrenheit) – especially for older adults who may not sweat as efficiently.

So environmental physiologist Fergus O’Connor, now at Griffith University in Brisbane, Australia, and colleagues decided to directly test the cooling power of fans during heat wave conditions. Study participants spent three episodes of eight hours each sitting in a room at the University of Ottawa, with the temperature set at 36°C (96.8°F) and 45 percent relative humidity. These conditions are similar to the climate Vancouver citizens endured during the week-long heat dome that settled over British Columbia in 2021, which led to an estimated 619 deaths in the province (SN: 7/7/21).

The climate-controlled room also had an electric fan. Previous models simulating the fan’s effectiveness assumed a fairly powerful airflow of about 3.5 to 4.5 meters per second. But that’s more power than many standard home fans are capable of, the researchers note. So each exposure period included a different fan speed: no airflow, a slow airflow of 2 meters per second, and a fast airflow of 4 meters per second.

The team then assessed the subjects’ body temperature, cardiovascular strain, level of dehydration and thermal comfort – the perception of feeling too hot or cold. The findings suggested that, compared with the control of no ventilatory airflow at all, the slower airflow did not result in significant changes in core temperature, blood pressure, fluid consumption, or thermal comfort. Faster airflow improved perceptions of thermal comfort—but, biophysically speaking, there was no significant improvement.