Electric Fans Increase The Thermal Strain In Older Adults Exposed To Very Hot And Dry Heat With Accompanying Activities Of Daily Living

Extreme heat can cause mass morbidity and mortality, with the elderly being amongst those most vulnerable to heat-related health complications. Indoor cooling with an air conditioner can prevent the adverse health effects of heat. However, air conditioning may not be available to many due to limited access, rising energy costs, power outages, and/or rolling blackouts. Electric fans provide a low-cost and accessible cooling intervention, yet their effectiveness is debatable due to potential risks of accelerated heat gain and dehydration in very hot conditions. PURPOSE: We tested the hypothesis that electric fans attenuate elevations in core temperature and the accompanying physiological strain in older adults exposed to very hot and dry heat with accompanying activities of daily living. METHODS: In a randomized order, 11 older adults (5 Females; 74 ± 5 years) were exposed to 3 hours of ambient heating, replicating peak environmental conditions during the 2018 Los Angeles heat wave (47 °C, 15% relative humidity), with (fan) or without (control) continuous electric fan exposure (~2 m/sec). To simulate heat generation associated with activities of daily living, participants performed six 5-minute periods of light exercise (~3 METS; metabolic heat production: 2.93 ± 0.40 W/kg in control and 2.96 ± 0.53 W/kg in fan) dispersed throughout the heat exposure. Participants consumed 3 mL/kg/hr of tap-temperature water. We assessed core and skin temperatures, heart rate, blood pressure, whole-body sweat rate, and forearm blood flow. We compared data between control and fan trials using one-tailed paired t-tests. RESULTS: When compared to control, fan use augmented the increase in core temperature by 0.61 ± 0.36 °C (p < 0.001), ending skin temperature by 1.45 ± 1.10 °C (p = 0.001), ending heart rate by 11 ± 12 bpm (p = 0.006), and ending rate pressure product by 1626 ± 2045 mmHg*bpm (p = 0.01). Whole-body sweat rate was 145 ± 64 g/hr (p < 0.001) greater and the change in forearm blood flow was 64 ± 78 mL/min (p = 0.01) higher with fan compared to control. CONCLUSION: These data show that electric fans appreciably increase the thermal and physiological strain in older adults exposed to extreme dry heat with accompanying activities of daily living. Thus, electric fans, as a cooling intervention, are not advised in the elderly under these conditions. NIH R01AG069005 (CGC) and AHA 23POST1023065 (ZJM)