Study objectives: The Epworth Sleepiness Scale (ESS) is widely used as a subjective measure of sleepiness. To our knowledge, no study has evaluated its reproducibility in the clinical setting.
Methods: A retrospective chart review of patients referred to the sleep clinic at Mount Sinai Hospital for evaluation of sleep-disordered breathing from a local private snoring clinic between January 2000 and October 2001 was carried out. Patients were snorers and referred because of suspicion of sleep apnea. Clinical information including results of the ESS scores from the two institutions was analyzed to evaluate reproducibility.
Results: There were 142 patients evaluated: 76% men with a mean (SD) age of 44 (11) years, body mass index of 31 (6.1) kg/m(2), and apnea-hypopnea index of 41 (34) events per hour. The average time interval between ESS administrations was 71 (92) days. The average ESS score was 11.1 (5.2) at the Snoring Clinic and 11.2 (5.3) at Mount Sinai Hospital. The Bland-Altman plot of the difference against the mean of the ESS score demonstrated a wide scatter of data and variability where 2 SDs ranged 7.8 above and below the mean. A difference between the sequential ESS scores of 5 or more was seen in 23% of the subjects.
Conclusion: The ESS score is highly variable when administered sequentially to a clinical population being evaluated for a potential sleep-related breathing disorder.