The association between obstructive sleep apnea (OSA) and cardiovascular disease is well known. Data from most studies investigating the prevalence of OSA in atrial fibrillation (AF), and of AF in patients with OSA, have supported the relationship between these common diseases. In addition, several studies have shown a detrimental effect of OSA on AF treatment. These reports vary considerably in methodology, and are particularly diverse in their definitions and diagnosis of OSA and patient populations studied. Considering these studies individually while exploring their methodological variations and the range of results achieved can reinforce the necessity of establishing standards for performing this important research. Reviewing these studies should encourage practitioners to reflect on how the methodologies, patients, and outcomes are relevant to their practices.