The Wagnerian leitmotif in this book on OSA is sleep position. OSA is a serious, highly prevalent disease with major health implications (chapters “Introduction” and “OSAS: The Magnitude of the Problem”). In the beginning of the book, the finding is highlighted that mild OSA in the majority of cases is positional (chapters “The Contribution of Head Position to the Apnea/Hypopnea Index in Patients with Position-Dependent Obstructive Sleep Apnea”, “Influence of Sleep Position on the Transition of Mild to Moderate and Severe OSA” and “Positional Therapy: Left Lateral Decubitus Position Versus Right Lateral Decubitus Position”). With progression of the disease from mild via moderate to eventually severe OSA, positional OSA progresses into non-positional severe OSA. In later chapters the observation is made that patients with insufficient response to therapy, such as can happen in palatal surgery, maxillomandibular advancement or bariatric surgery, severe non-positional OSA can reverse to less severe positional OSA (chapters “Positional OSA in the Morbidly Obese and the Effect of Weight Loss on OSA Severity”, “Positional Therapy and Tongue Base Surgery”, “Residual POSA After Maxillomandibular Advancement in Patients with Severe OSA”, “Impact of Upper Airway Surgery on Positional Change During Sleep” and “Comparison of Positional Therapy to CPAP in Patients with Positional Obstructive Sleep Apnea”). The circle is complete.

It has become clear that sleep position deserves a larger role in the management of sleep-disordered breathing, especially habitual snoring and OSA. In the first place, polysomnography positional sensing should routinely be included. Separate positional measurements for head and trunk during polysomnography should be seriously considered (chapter “The Contribution of Head Position to the Apnea/Hypopnea Index in Patients with Position-Dependent Obstructive Sleep Apnea”). Polysomnographic observations in various populations, sleep positions and sleep stages are discussed in chapters “Prevalence of Positional Obstructive Sleep Apnea in Patients Undergoing Polysomnography and the Effect of Sleep Stage”, “Clinical Characteristics of Positional Obstructive Sleep Apnea Among Asians” and “Positional Therapy: Left Lateral Decubitus Position Versus Right Lateral Decubitus Position”. Next in order, improvement of current drug induced sedated endoscopy methods by taking sleep position into account. For example, in cases with positional OSA undergoing DISE, observations in lateral sleeping position are mandatory (chapters “Drug-Induced Sleep Endoscopy and Sleep Position” and “Changes in Site of Obstruction in Obstructive Sleep Apnea Patients According to Sleep Position”). It is a clinical reality that, as yet, this is rarely done. Perhaps, tilting of the head during DISE is sufficient (chapter “Drug-Induced Sleep Endoscopy and Sleep Position”).