Introduction: Conventional measures of treatment efficacy (reduction in AHI) are poorly correlated with patient reported symptoms, such as measured by Epworth sleepiness scale (ESS). 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. Aim: To determine the relationship between Mean Disease Alleviation and symptoms of somnolence as measured by the Epworth Sleepiness Scale. Methods: Ninety-three patients were retrospectively analysed from a cohort of eight hundred and seventy adult OSA patients seen over a 13-year period. Patients were treated with continuous positive airway pressure (CPAP, n=40) or multilevel airway surgery (n=70). Mean disease alleviation was calculated as the product of efficacy (reduction in AHI) and adherence (derived from CPAP adherence reports). Surgical adherence was one hundred percent. ESS were collected in both treatment groups prior to and after therapy (while on CPAP or after surgery). Linear regression analysis was utilised to examine relationship between reduction in AHI, MDA and ESS. Results: The cohort’s average mean disease alleviation was 66.5 +/- 27.8%, with reduction in ESS from 11.6 to 5.0 (p < 0.05). The Pearson correlation coefficient for MDA and ESS in all patients was 0.15 (p > 0.1), 0.24 (p < 0.05) for surgery alone, and 0.00 (p > 0.05) for CPAP alone. Conclusion: Reduction in Epworth Sleepiness Scale is weakly correlated with Mean Disease Alleviation in surgical patients.