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Diagnosis

To define the severity of the condition, the Apnea-Hypopnea Index (AHI) or the Respiratory Disturbance Index (RDI) is used. While the AHI measures the mean number of apneas and hypopneas per hour of sleep, the RDI adds to this measure the respiratory effort-related arousals (RERAs). The OSA syndrome is thus diagnosed if the AHI is > 5 episodes per hour and results in daytime sleepiness and fatigue or when the RDI is ≥ 15 independently of the symptoms. Daytime sleepiness may be classified as mild, moderate, or severe depending on its impact on social life. Daytime sleepiness can be assessed with the Epworth Sleepiness Scale (ESS), a self-reported questionnaire on the propensity to fall asleep or doze off during daytime. Screening tools for OSA itself comprise the STOP questionnaire, the Berlin questionnaire and the STOP-BANG questionnaire which has been reported as being a powerful tool to detect OSA.