This review summarizes the recent literature on the epidemiology of adult obstructive sleep apnea (OSA) from various population-based studies. Despite methodologic differences, comparisons have yielded similar prevalence rates of the OSA syndrome in various geographic regions and across a number of ethnic groups. Risk factors for OSA including obesity, aging, gender, menopause and ethnicity, are analyzed. We also provide discussion on adverse medical conditions associated with OSA, including hypertension, stroke, coronary artery disease, congestive heart failure, cardiovascular mortality, insulin resistance and neurocognitive dysfunction. Finally, with the progression of the global obesity epidemic, we focus on the economic healthcare burden of OSA and the importance of recognizing the largely undiagnosed OSA population, with an emphasis on strategies to improve access to diagnostic resources.