Predictive factors of obstructive sleep apnoea in patients with fibrotic lung diseases

Several studies reported a high prevalence of Obstructive Sleep Apnoea (OSA) in patients with Idiopathic Pulmonary Fibrosis (IPF) or restrictive end-stage lung disease (ESLD). Besides the known risk factors for OSA like high Body Mass Index (BMI), reduced static and dynamic volumes for IPF patients and reduced DLCO and low minimal O₂ saturation during sleep for ESLD patients were associated with higher Apnoea-Hypopnoea Index (AHI). The aim of our study was to determine potential predictive factors of OSA in patients with Fibrotic Lung Diseases (FLD).

In this study, 49 patients with FLD and BMI ≤30 kg/m² were included. All patients underwent portable cardiorespiratory polysomnography (PSG) and were asked to fill in Epworth Sleepiness Scale (ESS). Their epidemiological, medication and subsidiary exams data were retrieved from their hospital records. Univariate and multivariate correlation models were obtained.

Approximately 70% of patients had an AHI ≥5 events/h. In an univariate correlation model, AHI showed a statistically significant correlation with age, BMI, the duration of immunosuppressant treatment, and Forced Expiratory Volume in the first second (FEV1). Only BMI remained an independent predictor of OSA in a multivariate correlation model adjusted for the other statistically meaningful variables.

FLD patients, in general, show a prevalence of OSA superior to that of the general population. Excess of weight might predict a higher risk for OSA in FLD patients. Larger and more homogenous studies are warranted to clarify the associations between OSA severity and lung function impairment and the duration of immunosuppressant treatment.