Two subtypes of positional obstructive sleep apnea: Supine-predominant and supine-isolated

•74% of obstructive sleep apnea (OSA) patients met the criteria for positional OSA (POSA).•Of those with POSA, 73% have supine-predominant OSA, and 27% supine-isolated OSA.•The supine-isolated OSA patients have less arousal but poorer sleep quality, and more depression.

ObjectivesThe body position has a strong influence on obstructive sleep apnea (OSA). The purpose of this study is to compare the clinical features of two subtypes of positional OSA (POSA), namely supine-predominant OSA (spOSA) and supine-isolated OSA (siOSA), so as to discuss whether the two groups can be classified separately.MethodsA total of 279 consecutive patients with OSA were enrolled. The POSA was defined as having an overall apnea-hypopnea index (AHI) ⩾5 with supine AHI >2 times the non-supine AHI. Only those with ⩾30 min spent in the supine and non-supine sleeping positions were included, and split night studies were excluded from the study. Patients were considered spOSA unless their non-supine AHI was negligible (<5) (siOSA). The clinical and polysomnographic characteristics of both groups were compared.ResultsTwo hundred and sixteen subjects (77.4%) met the criteria for POSA, with 158 (73.1%) of them classified as spOSA, and 58 (26.9%) as siOSA. The siOSA patients had lower arousal indices, but poorer quality of sleep, and were more depressed and anxious compared with the spOSA subjects.ConclusionsThose with siOSA and spOSA show different clinical features.SignificanceThese findings suggest that a more detailed sub-classification of POSA is needed.