Effects of ceiling fan use on cardiovascular autonomic function during simulated indoor overheating in bed-resting...

Older adults are at heightened susceptibility to heat-related cardiovascular complications when exposed to indoor overheating. While ceiling fans are recommended as an accessible cooling intervention, their effects on cardiac autonomic regulation remain unclear. In this randomized crossover study, 20 healthy older adults (median age 71 years, 12 female) completed two 8-h exposures to simulated indoor overheating (31°C, 45% relative humidity) while bed-resting with either no fan (control) or ceiling fan use (∼1.5 m/s airflow). Core temperature and heart rate were monitored. Before exposure and between hours 6 and 7, participants underwent cardiac autonomic response testing including measures of heart rate variability (SDNN, RMSSD - indices of overall and parasympathetic/vagal cardiac autonomic modulation, respectively) and supine-to-standing tests (30:15 ratio, systolic blood pressure response) as well as self-reported symptoms of orthostatic intolerance. Ceiling fan use reduced peak core temperature (0.2°C [95% CI: 0.1-0.3]; P < 0.001), heart rate (-5 beats/min [-10 to 0]; P = 0.03), and attenuated heat-induced reductions in RMSSD (4.7 ms [0.2-9.2]; P = 0.04) compared to control. However, fan use did not influence SDNN, blood pressure during postural changes, cardiac response to standing, or symptoms of orthostatic intolerance. While ceiling fans provided modest reductions in core temperature and heart rate and partially preserved RMSSD, they offered limited overall cardiovascular and autonomic protection in older adults during prolonged heat exposure. These findings indicate that, despite some beneficial effects, ceiling fans provide limited cardiovascular autonomic protection, underscoring the need for comprehensive cooling strategies to safeguard older adults during indoor overheating.