A polysomnography AHI rating of <5 is considered normal, 5-15 is mild and 15-30 is moderate, while anything over 30 is severe.
Normal: AHI<5 Mild sleep apnea: 5AHI<15 Moderate sleep apnea: 15AHI<30 Severe sleep apnea: AHI30 The ApneaHypopnea Index or ApnoeaHypopnoea Index (AHI) is an index used to indicate the severity of sleep apnea. Polysomnography (PSG), a type of sleep study, is a multi-parametric test used in the study of sleep and as a diagnostic tool in sleep medicine. 
