Association between mean disease alleviation and Epworth Sleepiness Scale in adult obstructive sleep apnoea (OSA)

Background: Conventional measures of treatment efficacy [reduction in Apnoea-Hypopnoea Index (AHI)] poorly correlate with patient reported symptoms, such as the Epworth Sleepiness Scale (ESS) in patients with obstructive sleep apnoea (OSA). Mean disease alleviation (MDA) takes into account treatment adherence and efficacy, and may offer a novel way to monitor sleep apnoea treatment and patient symptoms. This study aimed to determine the relationship between MDA and symptoms of daytime somnolence measured by the ESS.

Methods: This was a retrospective cohort study of adult patients treated for OSA, from a sleep clinic cohort, treated between 2008 and 2021. Patients with OSA were included in this study if they had been treated with continuous positive airway pressure (CPAP) or multilevel airway surgery, and also had pre- and post- treatment ESS and AHI data. MDA was calculated as the product of efficacy (reduction in AHI between pre-CPAP and CPAP sleep studies or pre- and post-surgery sleep studies) and adherence (derived from CPAP adherence reports or assumed as 100% for surgery patients). Pearson Correlation analysis was utilised to examine this relationship between reduction in AHI, MDA and ESS.

Results: One hundred and ten adult OSA patients met inclusion criteria for this study (CPAP, n=40; surgery, n=70). The cohort’s mean MDA was 66.5%±27.8%. The mean ESS decreased from 11.6±5.6 to 5.0±3.8, representing a mean reduction of 6.6 points [95% confidence interval (CI): 5.6–7.7; P<0.001]. There was a weak positive correlation between MDA and ESS in the surgical group (r=0.24, P=0.04), and no correlation in the CPAP group (r=0.00, P=0.99) or when all patients were pooled (r=0.15, P=0.12). The weak correlation seen in the MDA group was sensitive to removal of a single influential data point and should therefore be interpreted with caution.

Conclusions: Reduction in ESS is weakly correlated with MDA in surgical patients, but there is no correlation with MDA in CPAP patients. Given this correlation is limited, conventional means of measuring symptom improvement, such as the ESS, should still be routinely used in clinical practice to complement objective physiological data.