Correlation of the Epworth somnolence scale with the diagnosis andseverity of the obstructive sleep apnea-hypopnea syndrome (OSAHS)

Correlación de la escala de somnolencia de Epworth con el diagnóstico y severidad del síndrome de apnea hipopnea obstructiva del sueño (sahos)

Introduction: several publications have questioned the usefulness of the Epworth somnolence scale and suggest a lack of correlation with the severity of OSAHS given by the apnea-hypopnea index and with clinical outcomes.

Objectives: to determine the correlation index of the Epworth scale score and the sleep apnea-hypopnea index (AHI). To identify the cut point through the ROC Curve for the scale’s score and the AHI of the polysomnogram. To identify which variables of the scale correlate better with the diagnosis of OSAHS.

Design: descriptive cross-sectional study, correlation study. Determination of cut points by ROC curves.

Materials and methods: the database of patients who underwent baseline polysomnograms at the Clínica de Marly over the period from March 2005 to July 2009 and at the Hospital Universitario San Ignacio from March 2005 to February 2013 was used. Before the procedure, each patient was interviewed by a pulmonologist specializing in sleep, and a standardized survey was filled out. The demographic data of the population were established with the STATA 12.0 statistical program, and the correlation between the AHI and the Epworth score was studied. Different cut points were likewise studied by the ROC curve. Partial analyses were done by withdrawing, in a sequential process, variables of the Epworth scale in order to repeat the analyses, and the different degrees of severity were analyzed, separately in the AHI, in search of correlation.

Results: the data of 3093 patients (46,57% women) were analyzed. Their mean age was 56,52 years. The mean weight was 81,9±17.6 Kg with a mean BMI of 31,91 (±6,54) kg/m2. 87,78% of the patients had a BMI ≥ 25. OSAHS was diagnosed in 2667 patients (86,23%), with an AHI of 5 or more. The mean AHI was 32,76 (±29,05). On analysis, the correlation between the Epworth scale score and the AHI (Spearman’s rho) was 0,075 (p=0,0001), which shows there is no correlation. The ROC curve did not allow to choose any adequate cut point for the Epworth scale in regard to the diagnosis of OSAHS (area under the curve 0,52).

Conclusions: the result of the study shows us that the Epworth scale has no correlation with the AHI measured by polysomnography. No cut point with better sensitivity or specificity was found. Multidisciplinary evaluation and high diagnostic suspicion continue to be the best method for selecting patients who should undergo polysomnographic study.