Epidemiological investigation of a disease or a health condition basically aims to describe the occurrence of disease in the population [1]. Here the frequency, characteristics of the diseased individuals with the consideration of age, gender, place, and time are central. When we try to describe these features of sleep apnea, we have to take into account the specifics of sleep medicine which has gained tremendous advances after the revolutionary invention of EEG and standard recording of sleep and physiological changes during sleep. By this token, the definition of sleep apnea dates back to 1965 [2]. Description of a typical patient with obesity hypoventilation syndrome was coined with the Pickwick syndrome, due to the somnolent obese servant boy Jo.