The Sleep Position ‘Aid and Toll’ in Obstructive Sleep Apnea: A Lung-Brain Axis Perspective

Background: Supine sleep position has been shown to induce or aggravate sleep-breathing disorders, namely obstructive sleep apnea. In patients suffering from moderate-to-severe Obstructive Sleep Apnea-Hypopnea Syndrome (OSAHS), sleeping supine may significantly rise the Apnea-Hypopnea Index (AHI) scores, often causing profound oxygen desaturation. As such, OSAHSrelated complications would emerge secondary to chronic hypoxemia. In a fraction of cases where the condition is even more-strongly dependent to sleeping position, the term positional-OSAHS would apply. In this study, we examined the sleep position and other polysomnographic bioparameters in sleep apnea patients, in relation to their AHI and the incidence of concurrent medical conditions. This report also discussed the emerging evidence regarding the potential effects of sleep position and OSAHS on the brain. Materials and Methods: A retrospective analysis was done on 78 patients (mean age of 43.6 years), demonstrating increased AHI in supine compared to other positions, which referred to our sleep disorders unit and underwent polysomnography during 2013-2015. They were divided into mild (n=31) and moderate-to-severe (n=47) groups depending on their AHI scores (5=AHI=15 and AHI>15, respectively). Results: There found to be a significantly higher prevalence of hypertension, coronary artery disease and cerebrovascular disease in moderate-to-severe OSAHS patients. Likewise, Epworth Sleepiness Score (ESS) was notably higher and the mean oxygen saturation was lower in moderate-to-severe compared to mild OSAHS patients. Moderate-to-severe OSAHS cases were spending more time in supine rather than non-supine positions during sleep. AHIs and arousal index were found to be higher in supine position. Conclusion: Sleeping supine seems to worsen OSAHS and increase AHI, subsequently contributing to medical comorbidities. In case of positional- OSAHS, treatments should be individualized to prevent position-dependent airway collapse during sleep. Patients' awareness on the significance of sleep position in preventing OSAHS-related complications needs to be improved, and medically-proven interventions to maintain non-supine position during sleep should be advised in such patients.