Effects of Air Conditioning-Induced Humidity Reduction on Glomerular Filtration Rate in Healthy Adults

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.