The Montreal Heart Institute has conducted a significant study exploring the effects of electric fan use on older adults exposed to extreme heat. With growing concerns around heat-related health issues, particularly in vulnerable populations such as the elderly, this research provides insight into practical and safe cooling methods.

Research Overview

Published in JAMA Network Open, the study titled "Thermal and Perceptual Responses of Older Adults With Fan Use in Heat Extremes," aims to analyze the impacts of fan usage and skin wetting on core body temperature, sweating rates, and overall thermal comfort in older adults under extreme heat conditions. The research involved a cohort of 58 elderly participants, averaging 68 years old, including individuals with coronary artery disease.

Study Design

The researchers conducted a secondary analysis of a randomized crossover clinical trial, where subjects were exposed to two different temperature and humidity environments:

  • 38 °C and 60% relative humidity
  • 45 °C and 15% relative humidity

Each participant underwent a total of 320 laboratory heat exposures. In the humid trial, subjects experienced four randomized conditions:

  1. Control
  2. Fan alone
  3. Skin wetting alone
  4. Combined fan plus skin wetting

In the dry heat condition, participants limited to control and skin-wetting sessions were particularly monitored due to their health status.

Key Findings

The results revealed critical differences in the effectiveness of fan use based on humidity levels:

Condition Effect of Fan Use Effect of Skin Wetting
38 °C and 60% RH
  • Lowered rectal temperature by −0.1 °C
  • Increased sweat rate by 57 mL/h
  • Improved thermal sensation by −0.6 AU
  • Enhanced comfort by −0.6 AU
  • Reduced sweat loss by 67 mL/h
  • Improved sensations significantly
45 °C and 15% RH
  • Increased core temperature by 0.3 °C
  • Boosted sweating by 270 mL/h
  • Worsened sensation and comfort by 0.5 AU each
  • Lowered sweating by 121 mL/h
  • Enhanced sensation by −0.4 AU

Implications for the Elderly

These findings suggest that while fans can be beneficial in humid conditions, they should be avoided during extremely hot and dry conditions. The combination of fans and skin wetting showed the most substantial improvement in thermal sensations, indicating that moisture can aid in cooling during severe heat exposure.

“Our study illustrates the complexities of heat exposure for older adults and emphasizes the need for targeted public health messages to ensure their safety in extreme temperatures.” – Dr. Georgia K. Chaseling, Lead Researcher

Public Health Recommendations

The study's findings may prompt public health agencies to refine their summer heat safety guidelines for seniors. Recommendations may include:

  • Encouraging fan use when humidity is high and temperatures are moderate.
  • Promoting skin wetting techniques as a reliable way to mitigate heat stress.
  • Advising against using fans in very hot and dry environments.

Conclusion

As heat-related health risks continue to escalate, particularly for older adults, the implementation of effective cooling strategies becomes increasingly essential. This research provides valuable insights that can help shape effective interventions aimed at enhancing the safety and comfort of vulnerable populations during extreme temperature events.

References

Chaseling, G. K., et al. (2025). Thermal and Perceptual Responses of Older Adults With Fan Use in Heat Extremes. JAMA Network Open. Retrieved from https://medicalxpress.com/news/2025-07-fan-older-adults-hotter-dry.html.