To our knowledge, no study has examined the persistence of sleep disordered breathing in acute coronary syndrome (ACS) patients. We examined the time course of SDB in ACS patients by assessing them within days of the acute event and again after 6 months. Consecutive patients with ACS were asked to voluntarily participate in the study. Patients underwent an overnight polysomnography (PSG) approximately 3 days after the acute event. Patients with an apnea hypopnea index (AHI) > 10/h then underwent another PSG after they were stable (approximately 6 months). Fifty patients were studied. First PSG showed an AHI was 23.1 +/- 3.6/h. A second PSG was performed 6.1 +/- 0.3 months later on 21 patients and showed an AHI > 10/h in the first assessment. The AHI and the obstructive apnea index did not change over the 6 months. However, the central apnea index all was lower at the second assessment.