The Epworth sleepiness scale: relationship to sleep and mental disorders in a sleep clinic

Background and purpose: Both sleep disorders and mental disorders are associated with excessive daytime sleepiness as measured by the Epworth sleepiness scale (ESS). We sought to assess the relationship between the ESS scores and mental disorders in a sleep clinic. Methods: One hundred sixty-five consecutive new referrals to a sleep clinic completed the ESS prior to their initial visit. Mental disorders (major depression, minor depression, anxiety not otherwise specified, and panic disorder) were diagnosed with the primary care evaluation of mental disorders (PRIME-MD) questionnaire, a reliable and valid instrument. Nearly all sleep diagnoses (95%) were made by polysomnography. Results: The mean ESS for the cohort was 12.3 (standard deviation (SD) 5.1). There was no difference in the mean ESS for those with and without mental disorders (12.8 vs. 12.2, P=0.48) or sleep-disordered breathing (SDB) (12.3 vs. 12.3, P=0.99). ESS scores were not different between patients with a comorbid mental disorder and SDB compared with the presence of a mental disorder or SDB alone (combination: 13.0 vs. mental disorder: 11.5 vs. SDB: 12.2, P=0.70). There was also no relationship between ESS scores and the respiratory disturbance index (RDI) (P=0.63). Conclusions: We found no relationship between ESS scores and mental disorders among referrals to a sleep clinic. ESS cannot be used to screen for mental disorders among sleep clinic patients.