Preserved ratio impaired spirometry and severity of obstructive sleep apnea: An observational cross-sectional study

Background and objective: Lung function abnormality of obstructive sleep apnea (OSA) has not been explored well. Preserved ratio impaired spirometry (PRISm) is known for its association with obesity and cardiovascular morbidity, which are also characteristic features of OSA. This study aims to investigate whether the prevalence of PRISm increases according to apnea-hypopnea index levels among subjects with OSA. Methods: Conducted as an observational cross-sectional study, the study included 372 patients >= 40 years of age with definitive diagnoses of OSA and pulmonary function assessment from 2000 to 2004. Study subjects were classified based on OSA severity (mild/moderate versus severe). The prevalence of PRISm was estimated and compared between mild/moderate and severe OSA groups. Results: The prevalence of PRISm was 9.4 % in study subjects, with a higher prevalence in the severe OSA group than the mild/moderate group (12.9 % and 6.2 %, respectively, P = 0.04). The positive association between severe OSA and PRISm remained robust after multivariable adjustment for age, gender, and obesity (multivariable-adjusted odds ratio 2.29 (95 % confidence intervals 1.08-4.86), P = 0.03). Conclusion: Severe OSA is an independent risk factor for PRISm, highlighting the need for comprehensive management of OSA that addresses the potential risk of PRISm.