Pulmonary Function in Obese Snorers with or without Sleep Apnea Syndrome

Abstract

We evaluated pulmonary function abnormalities associated with the sleep apnea syndrome (SAS) in 170 habitual snorers without SAS (n = 62, apnea-hypopnea index [AHI] < 10 per hour of sleep), with moderately severe SAS (n = 56, 10 < or = AHI < 30) or with severe SAS (n = 52, AHI > or = 30). The three groups were similar regarding obesity (BMI approximately 30 kg.m-2) and smoking history (approximately 20 pack-years). Pulmonary function was assessed by spirometry, forced oscillation mechanics, and gas exchange studies. Forced expiratory flows decreased as the SAS severity increased (p < 0.001, p < 0.02, and p < 0.05 for FEF50, FEV1, and FEV1/VC, respectively). Multiple regression analysis showed that the correlation between FEV50 and the AHI persisted when smoking history was taken into account (p < 0.05), suggesting that SAS may be an independent risk factor for small airway disease. A highly significant correlation was found between specific respiratory conductance (sGrs) and the AHI (p < 0.0001). In a multiple regression analysis (p < 0.0001), variables that influenced sGrs were distal airway obstruction as assessed by FEV50 (p < 0.05), morphological upper airway abnormalities as assessed by cephalometric parameters (p < 0.02), and the AHI (p < 0.0005). SAS appears to be highly correlated to lower and upper airway obstruction, as demonstrated by a reduction in specific respiratory conductance, which adds to the increase in breathing load due to obesity.