Obstructive positional sleep apnea. Prevalence and characteristics.

Positional obstructive sleep apnea (POSA) is one of the most prevalent phenotypes within obstructive sleep apnea (OSA). The aim of the present study is to determine the prevalence of POSA according to the Amsterdam Positional OSA Classification (APOC), recently introduced, and to characterize it in our area. We included 409 patients consecutively referred to the sleep clinic of the Pulmonology Department at Hospital Universitario Río Hortega de Valladolid between July 2016 and April 2018. All patients underwent home polysomnography. The APOC classification was utilized to evaluate positional apnea, wherein patients should exhibit an AHI > 5 and more than 10% of events in both supine and non-supine positions. Valid polysomnographies were included in the study, as well as those patients who demonstrated an AHI > 5 and more than 10% of time spent in the supine position. Finally, 233 patients were included. A total of 48.1% exhibited severe obstructive sleep apnea. Among the patients, 55.4% were classified as POSA positive. Within this group, 28.6% were categorized as APOC I, 59.6% as APOC II, and 11.8% as APOC III. POSA patients, compared to non-POSA patients, had a lower BMI (27.7 vs. 29.8, p<0.05), a lower percentage of N1, lower AHI in REM and non-supine phases and lower CT90. There were differences regarding quality of life, particularly in the anxiety module. Time spent in the supine position increased with the severity of APOC. Significant differences in AHI were observed according to APOC classification, with lower values in APOC I patients. The prevalence of positional sleep apnea was high according to APOC criteria. One third of positional patients were strictly positional (APOC I).