Nocturnal hypoxaemia is associated with adverse outcomes in interstitial lung disease

Background and objective Sleep-disordered breathing (SDB) has been reported as highly prevalent in idiopathic pulmonary fibrosis (IPF) and other interstitial lung disease (ILD) populations. Nocturnal oxygen desaturation (NOD), or the total sleep time spent with SpoO(2) < 90% (TST < 90), can occur both with and without associated apnoeas, and is common in ILD. This study aimed to characterize abnormal SDB and extent of TST < 90 in ILD patients and evaluate relationships between TST < 90 and markers of disease severity, development of pulmonary hypertension (PH) and mortality. Methods Consecutive, newly referred ILD patients attending a specialist clinic underwent polysomnography (PSG). Serial lung function tests, echocardiography and other clinical variables were recorded. Predictors of PH and mortality were evaluated using logistic regression and Cox proportional hazards regression analyses. Results A total of 92 ILD patients (including 44 with IPF) underwent PSG. At least mild obstructive sleep apnoea (OSA) was observed in 65.2%, with rapid eye movement (REM)-related events occurring frequently. At least 10% TST < 90 (designated 'significant NOD') was present in 35.9% of patients, and was associated with PH at baseline echocardiography. Multiple indices of hypoxaemia during sleep, including significant NOD, predicted the development of new or worsening PH. TST < 90 predicted overall and progression-free survival. Conclusion Nocturnal oxygen saturation is associated with poorer prognosis in ILD patients and may contribute towards the pathogenesis of pulmonary vascular disease.