Ceiling Fans During Bedrest As A Cooling Strategy For Older Adults During Indoor Overheating

Recent guidance has recommended the use of electric fans as a sustainable cooling alternative to air conditioning for heat vulnerable populations. While fans may increase sweat evaporation and heat loss in healthy, young adults, evidence supporting their use in older adults is scarce. In this context, many health-care facilities and long-term care homes do not have air-conditioning and rely on ceiling fans to provide relief during daylong bedrest. While recent biophysical modelling has suggested that fans may provide a clinically meaningful cooling effect in temperatures below ~34 °C in older adults, the efficacy of ceiling fans in mitigating heat strain in these conditions is unknown. PURPOSE: To assess the effect of ceiling fans on thermal, cardiovascular, and perceptual strain in older adults during bedrest in a simulated overheated indoor environment. METHODS: We assessed the change in core temperature, heat rate, rate-pressure product and thermal discomfort before and after daylong indoor overheating (8-h, 31 °C, 45% relative humidity) with or without the use of a commercially available ceiling fan providing a standard airflow in 20 older adults (12 female, median age 71 [IQR: 68, 73]) resting on a medical bed. Data were analyzed with linear mixed-effects models (baseline adjusted; 2-tailed α = 0.05). RESULTS: The increase in rectal temperature from pre- to end-exposure was 0.1 [95% CI: 0.0, 0.2]°C lower with fan use (0.7 °C (SD 0.3 °C)) compared to control (0.9 °C (0.3 °C); P = 0.023). The pre-end-exposure change in heart rate was reduced 2 [0, 4] beats/min with a fan (11 (4) vs. 9 (5) beats/min in control; P = 0.032) but there were no between-condition differences in rate-pressure product (fan use - control difference: -125 [-474, 223] mmHg·beats/min, 712 (912) vs. 867 (633); P = 0.480) mmHg·beats/min). Self-reported thermal discomfort was reduced 9 [4, 14] units with a fan (12 (8) units) compared to control (3 (8) units; P < 0.001). CONCLUSIONS: Ceiling fans may improve thermal comfort but only had small benefits on core temperature and heart rate and little influence on rate-pressure product during bed rest when exposed to daylong indoor overheating. Fans should be paired with additional cooling strategies (e.g., ambient cooling). Supported by: Canadian Institutes of Health Research and Health Canada