Sleep-disordered breathing (SDB) and cardiovascular disease (CVD) are closely related; however, the effect of SDB on the long-term prognosis of patients with CVD is unknown. Our aim in this study was to assess the association between SDB and fatal cardiovascular events in patients with CVD. We performed a long-term follow-up study of 135 patients with CVD. The average observation period was 610 +/- 268 days. The patients were classified into 2 groups based on their apnea index: patients with apnea index >or=5/h (Group H) were diagnosed with SDB (n = 43), and those with apnea index <5/h (Group L) were diagnosed without SDB (n = 92). In Group H, obstructive sleep apnea (OSA) was diagnosed if obstructive apnea index was >or=5/h, and central sleep apnea was diagnosed if central apnea index was >or=5/h. Group H had a significantly lower survival rate than Group L (p <0.005), particularly those with OSA in Group H (p <0.0005). In a Cox proportional hazards model with presence of OSA, age, brain natriuretic peptide, left ventricular ejection fraction, and cardiovascular risk factors, the odds ratio of fatal cardiovascular events was 2.45 (95% confidence interval 1.26 to 5.08) for OSA (p <0.01), which was associated with an increased risk of mortality. In conclusion, our results suggest that SDB is associated with a poorer long-term prognosis and that the presence of OSA is a strong predictor of fatal cardiovascular events in patients with CVD.