Subjective apnoea symptoms are associated with daytime sleepiness in patients with moderate and severe obstructive sleep apnoea: a retrospective study.

OBJECTIVES: Most previous studies have failed to show a relation between daytime sleepiness and apnoea severity in patients with obstructive sleep apnoea (OSA). We determined the relation between daytime sleepiness and subjective and objective apnoea severity in newly diagnosed patients with moderate-to-severe OSA.

DESIGN: Retrospective cross-sectional study.

SETTING: Tertiary referral centre.

PARTICIPANTS: A total of 559 adults with newly diagnosed moderate and severe OSA.

MAIN OUTCOME MEASURES: Daytime sleepiness was evaluated using the Epworth Sleepiness Scale (ESS). Subjective and objective apnoea severities were assessed using the Sleep Breathing Scale (SBS) and polysomnography respectively. Sleep quality and depressive symptoms were evaluated using Medical Outcomes Study-Sleep Scale and Beck Depression Inventory (BDI) respectively.

RESULTS: The mean ESS score was 9.8 (SD 5.0). ESS score was correlated with SBS score (P < 0.001), apnoea-hypopnoea index (AHI) (P = 0.027), minimal oxygen saturation (MinSaO2 ) (P = 0.021), body mass index (BMI) (P = 0.007) and BDI score (P < 0.001). Linear regression analysis showed that higher SBS (P = 0.005) and BDI scores (P < 0.001) were associated with higher ESS score after controlling for gender, BMI and AHI. Apnoea-hypopnoea index, MinSaO2 and BMI were not independently related to ESS score.

CONCLUSIONS: Daytime sleepiness was related to subjective OSA symptoms but not objective apnoea severity measured by polysomnography in patients with moderate-to-severe OSA. These findings suggest the usefulness of the subjective apnoea severity as an indicator of OSA disease severity.