Purpose: Sleep and sleep position have a significant impact on physical, cardiac and mental health, and have been evaluated in numerous studies particularly in terms of lateral sleeping positions and their association with diseases. We retrospectively examined the relationship between the sleeping position and position-specific apnea-hypopnea index (AHI) in obstructive sleep apnea-hypopnea (OSA) patients.

Methods: We assessed the sleeping body position and the body position-specific AHI score in patients who were referred for suspected OSA and underwent diagnostic nocturnal polysomnography. In order to eliminate inter-individual differences, only those who had a similar percentage of time spent in the LSSP and RSSP for each patient were enrolled. To provide this validity, only subjects that had a similar percentage of left and right lateral sleep time (±10%) were included in the analysis.

Results: A total of 864 patients had nocturnal diagnostic PSG. Of them, 131 patients met the inclusion criteria. The percent rate spent in the supine sleeping position (SSP) was 31.3 ± 18.7%, in the LSSP was 31.8 ± 10% and in the RSSP was 32.6 ± 10.8%. Whereas the SSP-specific AHI score was the highest with 60.4 ± 36.2/h among all the sleeping position-specific AHI scores (p < 0.001), the LSSP-specific AHI score was statistically higher than that for RSSP (30.2 ± 32.6/h vs. 23.6 ± 30.1/h; p < 0.001). When comparing individuals sub-grouped based on OSA severity, there was a statistically significant difference between the LSSP-specific AHI score and RSSP-specific AHI score in patients with severe (p = 0.002) and moderate (p = 0.026), but not mild (p = 0.130) OSA.

Conclusion: We found that the sleeping position had a significant influence on apneic events and RSSP decreased the frequency of obstructive respiratory events in patients with moderate and severe disease.