['From 1984 to 2006, studies of sleep in patients with interstitial lung disease revealed disturbed sleep, frequent nocturnal desaturations, nocturnal cough, and obstructive sleep apnea (OSA). Our goal was to analyze OSA in an outpatient population of stable patients with idiopathic pulmonary fibrosis (IPF).', 'Patients with IPF who had been followed up in the Vanderbilt Pulmonary Clinic were asked to participate. All patients were given a diagnosis of IPF by the 2000 American Thoracic Society consensus statement criteria. Subjects completed an Epworth sleepiness scale (ESS) questionnaire and a sleep apnea scale of sleep disorders questionnaire (SA-SDQ) before undergoing nocturnal polysomnography (NPSG). OSA was defined as an apnea-hypopnea index (AHI) of > 5 events per hour.', 'Fifty subjects enrolled and completed a NPSG. The mean age was 64.9 years, and the mean BMI was 32.3. OSA was diagnosed in 88% of subjects. Ten subjects (20%) had mild OSA (AHI, 5 to 15 events per hour), and 34 subjects (68%) had moderate-to-severe OSA (AHI, > 15 events per hour). Only 6 subjects (12%) had a normal AHI. One patient was asymptomatic as determined by ESS and SA-SDQ, but had an AHI of 24 events per hour. The sensitivity of the ESS was 75% with a specificity of 15%, whereas the SA-SDQ had a sensitivity of 88% with a specificity of 50%. BMI did not correlate strongly with AHI (r = 0.30; p = 0.05).'] Is obstructive sleep apnea common in idiopathic pulmonary fibrosis?