The Role of Lung Volume, Age, and Body Mass Index in Determining Obstructive Sleep Apnea Severity

Background and Objectives: It is well established that obstructive sleep apnea syndrome (OSAS) is associated with functional lung volumes. The aim of this study was to investigate the relationship between morphological lung volume and the severity of OSAS. Materials and Methods: Adult patients evaluated for sleep disorders between January 2020 and January 2024 were retrospectively reviewed. Patients with an AHI greater than 5, who underwent both spirometry and thoracic CT within a three-month interval, were included. Spirometric functional volume and morphological CT lung volume were assessed. Associations between OSAS severity and both functional and morphological lung volumes were analyzed. Results: A total of 195 patients were enrolled, of whom 166 had CT scans suitable for lung volume assessment. Among all patients, 20 (10.3%) were in the mild, 39 (20.0%) in the moderate, and 136 (69.7%) in the severe OSAS group. Ordinal regression analysis was performed to evaluate the factors influencing these categories. Age (p < 0.001) and BMI (p < 0.001) were positively correlated with disease severity, whereas female sex was associated with a lower risk of severe disease (p = 0.003). Conclusions: Functional and morphological lung volumes did not affect OSAS severity. Functional and morphological lung volumes were positively correlated with each other. Both morphological and functional lung volumes showed negative correlations with BMI.