ACE and sleep apnea syndrome: This discrepancy between our studies is intriguing but might be explained by the higher prevalence of heart failure in the sleep apnea (+) DM (+) group, which was indicated by the lower left ventricular ejection fraction on echocardiography and more frequent use of diuretic, β-blocker, and angiotensin converting enzyme inhibitor/angiotensin receptor blocker therapies in the sleep apnea (+) DM (+) group relative to the other three groups in this analysis.