Background: In the outpatient setting, untreated obstructive sleep apnea (OSA) is associated with myriad adverse clinical outcomes including myocardial infarction, heart failure, arrhythmias, and cerebrovascular disease.  However, little is known about the impact of treated versus untreated OSA on short-term outcomes in patients hospitalized with acute illness. We propose that the recurrent hypopnea and apnea [...]