Abstract
BACKGROUND Air conditioning reduces indoor humidity, which can affect fluid balance and renal function. This study assessed the effect of short-term humidity reduction on estimated glomerular filtration rate (eGFR) in healthy adults. MATERIAL AND METHODS We conducted a cross-sectional and a self-controlled study in southern China enrolling. In the cross-sectional study, 12 671 healthy adults aged 18-75 years. There were 7120 participants in the air conditioning group (ACG) and 5551 in the electric fan group (FG), and. In the self-controlled study, 362 participants (mean age: 42.9±11.7 years) were exposed to both environments sequentially. Indoor humidity and temperature were recorded overnight using digital sensors. After 8 hours of sleep, fasting blood and urine samples were collected. eGFR was calculated using the Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. RESULTS In the cross-sectional study, indoor humidity was lower in the air conditioning group (ACG: 48% [44-52%]) compared to the fan group (FG: 80% [77-83%], P<0.001). Mean eGFRMDRD was significantly lower in the ACG (105.3±16.5 mL/min/1.73 m²) than in the FG (109.1±17.0 mL/min/1.73 m², P<0.001). In the self-controlled study, eGFRMDRD was also reduced after air conditioning exposure (104.6±15.8 vs 108.4±15.7 mL/min/1.73 m², P<0.001). CONCLUSIONS Low indoor humidity due to air conditioning is associated with a modest but significant decline in eGFR in healthy adults.