Sleep-disordered breathing (SDB) is considered to be closely related to lifestyle diseases such as heart disease, hypertension, and diabetes. Its strong relationship with various cardiovascular (CV) disorders has recently become recognized in Japan. The diagnosis and treatment of SDB appears to affect the prognosis of CV disorders. Accordingly, doctors specializing in CV disorders need to be involved in the management of SDB. However, the level of involvement has not been sufficient to date. The author(s) conducted coronary bypass surgery on a patient, but the postoperative decline in heart function persisted. Upon in-depth examination, SDB was revealed. For this patient, continuous positive airway pressure drastically improved the ejection fraction from 40% to 65%. Since then, we have used a portable sleep Polygram instrument to screen heart surgery patients (1,005 patients) for the first time worldwide (NU-SLEEP study). SDB was observed in 77% of the patients. Among them, 16% of patients had severe SDB. These results indicate a strong association between CV disorders and SDB. In this featured article on SDB, the author(s) summarizes the involvement of SDB in various CV disorders.