SYDNEY, July 31, 2025 – Electric fans may do more harm than good for older adults in extreme dry heat, according to new research that challenges long-standing heatwave advice.
A study published this week in JAMA Network Open reveals that while fans can modestly cool seniors in hot, humid weather, they may actually raise core body temperatures and increase cardiovascular strain in dry, arid heat – a growing concern in a warming world.
The clinical trial, led by scientists from the University of Sydney, Monash University, University of Adelaide and the Montreal Heart Institute, tested 58 healthy older adults with an average age of 68. Participants were exposed to two heatwave simulations in a controlled climate chamber: one mimicking a 38 °C (100.4 °F) environment with 60% relative humidity, and another mimicking a 45 °C (113 °F) environment with just 15% humidity – typical of dry inland heatwaves increasingly common in countries like Australia and the United States.
During the humid condition, fan use resulted in a modest cooling effect, lowering core body temperature by around 0.1 °C (0.18 °F). Participants also reported improved comfort and demonstrated increased sweating, a key mechanism the body uses to shed heat. But in the hotter, dry setting, fan use backfired. Participants’ core temperatures rose by about 0.3 °C (0.54 °F), and they reported increased heat discomfort – findings that suggest fans might exacerbate rather than ease heat stress in these conditions.
This rise in core temperature is particularly significant for older adults, whose ability to regulate body temperature diminishes with age. Many also live with cardiovascular conditions that can make them more vulnerable to overheating. The increased skin blood flow and cardiovascular strain observed in the study under dry-heat conditions with fan use could pose real health risks during prolonged heatwaves.
Notably, the study also evaluated the effectiveness of wetting the skin with a sponge, a simple cooling intervention. This approach consistently improved thermal comfort across both conditions, though it did not significantly reduce core body temperature.
The findings complicate heatwave advice issued by public health authorities like the U.S. Centers for Disease Control and Prevention (CDC), which currently advises against fan use when indoor temperatures exceed 32 °C (89.6 °F), citing concerns about ineffective cooling. However, the new study suggests that relative humidity should also be factored in when determining whether fan use is safe – particularly for older adults, who account for the majority of heat-related deaths.
As global temperatures rise and extreme heat events become more frequent and intense, experts say tailored cooling guidance for older people is essential. The research underscores the need for low-cost, accessible strategies – like skin wetting and access to air-conditioned spaces – to protect vulnerable populations during dangerous heat events.