**7. Classification of OSAS**

The severity of OSAS can be classified into three groups according to the apnea-hypopnea index (AHI). An AHI score smaller than 5 is considered normal. An AHI score between 10 and 20 represents mild obstructive sleep apnea, AHI score of 21–40 represents moderate obstructive sleep apnea, and AHI score greater than 40 represents severe obstructive sleep apnea [10–12, 22].
