Obstructive Sleep Apnoea (OSA) is a common disorder linked to significant comorbidities. Emerging research highlights the crucial role of sleeping position in OSA severity and management.
Defining and Characterising Positional OSA (POSA)
POSA describes a subtype of OSA where respiratory events are significantly exacerbated in the supine position. A study, published in the Journal of Clinical Sleep Medicine and utilising data from the extensive Sleep Heart Health Study (SHHS) cohort, defined POSA based on a supine apnoea-hypopnea index (AHI) at least double the non-supine AHI, with an overall AHI ≥5 events/hour. A noteworthy finding was the high prevalence of POSA, identified in 62% of the 1,870 participants with OSA, indicating that positional dependency is a dominant feature for the majority of patients.
Subtypes of POSA: Clinical Implications
The research further delineates POSA into two distinct subtypes with differing clinical characteristics and therapeutic implications:
- Supine-Isolated OSA (siOSA): This stricter form of positional dependency is characterised by a normalisation of respiratory events (non-supine AHI <5 events/hour) when the patient avoids the supine position. SiOSA was observed in 44% of the POSA cohort and tends to present in younger, less obese individuals, with a higher prevalence in females.
- Supine-Predominant OSA (spOSA): In contrast, spOSA signifies that while respiratory events are worse in the supine position, the non-supine AHI remains elevated (≥5 events/hour). This subtype was more common, accounting for 56% of POSA cases. SpOSA is associated with a higher overall AHI, greater sleep fragmentation, and a higher proportion of moderate to severe OSA compared to siOSA.
Key Takeaways for General Practice
- Prevalence: Positional Obstructive Sleep Apnoea (POSA) is remarkably common, affecting over 60% of individuals with OSA.
- Subtyping: POSA is heterogeneous, comprising supine-isolated (siOSA) and supine-predominant (spOSA)
- Clinical Severity: The spOSA subtype is more prevalent and is associated with greater OSA severity and a higher burden of metabolic and cardiovascular comorbidities (diabetes, hypertension) compared to siOSA.
- Personalised Treatment: Identifying the specific POSA subtype is crucial for tailoring therapeutic approaches, with positional therapy being a viable and effective option for siOSA, while spOSA and non-positional OSA necessitate broader interventions such as CPAP.
Reference
Duce, B.L., Kulkas, A.E., Leppänen, T.T., Oksenberg, A., Töyräs, J., & Hukins, C.A. (2025). Community prevalence of positional obstructive sleep apnea. Journal of Clinical Sleep Medicine, 21(5), 875-882
