BACKGROUND: Interstitial lung diseases (ILD) are chronic and restrictive lung diseases with poor survival and quality of life. The aim of this study was to investigate the frequency of sleep disorders in idiopathic pulmonary fibrosis (IPF) and sarcoidosis and to assess patients' quality of life in relation to these disorders.METHODS: Forty patients, 19 with IPF, and 21 with sarcoidosis stage II/III were included. They were compared with 15 healthy subjects. All patients performed all-night polysomnography (PSG) and completed the Epworth, Berlin, and Stop-Bang questionnaires. In order to evaluate the quality of life, all patients completed the Short-Form 36 (SF-36) questionnaire.RESULTS: Of the IPF patients, 68% were diagnosed with mild obstructive sleep apnea (OSA), 5.2% with moderate to severe, 5.2% with severe OSA, and 21% with no OSA. Of patients with sarcoidosis, 52.4% were diagnosed with mild OSA and 4.8% with moderate severity OSA. The remaining 42.8% did not have OSA. The health-related quality of life in both patients with IPF and patients with sarcoidosis was impaired especially in the domains concerning physical health and the level of independence, compared to the control group.CONCLUSIONS: In this sample of patients with IPF and sarcoidosis, obstructive sleep apnea is common at least in a mild degree of severity. The SF-36 questionnaire may be a useful tool for the evaluation of the quality of life in these patients.