Objectives: The 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.
Methods: A total of 279 consecutive patients with OSA were enrolled. The POSA was defined as having an
overall apnea-hypopnea index (AHI) P5 with supine AHI >2 times the non-supine AHI. Only those with
P30 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.
Results: Two 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.
Conclusions: Those with siOSA and spOSA show different clinical features.
Significance: These findings suggest that a more detailed sub-classification of POSA is needed.