Positional obstructive sleep apnea and cardiovascular outcomes.

Background: A tendency to obstruct the upper airway is markedly increased in supine sleep. Positional obstructive sleep apnea (OSA) (POSA) occurs predominantly in the supine position. The implication of POSA in terms of future cardiovascular (CV) risk is unknown. We hypothesized that patients with POSA have decreased future CV risks compared to OSA patients without POSA (non-POSA).

Methods: This single-center study included patients who underwent clinically indicated polysomnography. POSA was defined as an apnea-hypopnea index (AHI) ≥ 5 events/hour and supine AHI at least twice as high as non-supine AHI (nsAHI). Exclusive POSA (ePOSA) includes the additional requirement that the nsAHI normalizes to an AHI of < 5/hour. A Cox proportional hazard model was used to assess the future risk of new CV events in patients with POSA compared to non-POSA (reference group).

Results: There were 3,779 patients (mean age 51, female 59.7%), consisting of 35.9% POSA, 38.4% non-POSA, and 25.7% no OSA. Using the ePOSA definition, 17.3% had ePOSA, 57.1% had non-ePOSA, and 25.7% had no OSA. Over a median 8.4 years, there were 1,297 composite events. Patients with POSA had a lower risk of CV events compared to non-POSA (HR 0.85, CI:0.74-0.96; p = 0.010). There was a non-significant trend towards lower risk of CV events in patients with ePOSA compared to non-ePOSA (HR 0.86, CI:0.73-1.01; p = 0.061).

Conclusions: POSA is associated with lower CV risk than non-POSA. Future studies should consider POSA as a distinct subtype when studying OSA and CV outcomes.