The Epworth Sleepiness Scale: self-administration versus administration by the physician, and validation of a French version

Abstract

Background/objectives: The Epworth Sleepiness Scale (ESS) measures sleepiness and is used for, among others, patients with obstructive sleep apnea (OSA). The questionnaire is usually self-administered, but may be physician administered. The aim was to compare the two methods of administration and to validate a French version.

Methods: Consecutive patients presenting to the sleep clinic at a tertiary care centre completed a self-administered questionnaire containing the ESS. During the medical interview the same day, one of three pulmonologists who specialized in sleep medicine administered the ESS. Correlations with the apnea-hypopnea index and mean sleep latencies were used to assess construct validity, while results of previous self-administered ESS questionnnaires in untreated and recently treated OSA patients were used to test reproducibility and longitudinal construct validity, respectively.

Results: In OSA patients, the ESS weakly correlated with the apnea-hypopnea index (r=0.224; P=0.05; n=120) and negatively with mean sleep latency. For untreated patients (test-retest), the mean (+/- SD) average score was unchanged (10.3+/-6.0 to 10.8+/-6.5; P=0.35; n=56) after a median of seven months. With continuous positive airway pressure use, the mean score decreased from 12.4+/-6.8 to 7.6+/-5.0 after 40.2 months (P<0.0001; n=68). For all subjects, the ESS score obtained by the physician was less than that of the self-administered result (9.4+/-5.9 versus 8.5+/-5.8; P<0.0001 [paired t test]; n=188).

Conclusions: In a sleep clinic population, the French version of the ESS performed similarly to the English version. However, the systematic underscoring during physician administration may be important to consider in the research setting if questionnaire administration methods are not consistent.

Figure 1)

Correlation between the Epworth sleepiness scale (ESS), before any treatment initiation, and the apnea-hypopnea index (AHI) in 124 obstructive sleep apnea subjects

Figure 2)

Distribution of Epworth Sleepiness Scale (ESS) scores versus (A) mean electroencephalogram (EEG)-derived sleep latency (MSL_EEG) (sleep onset defined as the first epoch of any sleep stage), (B) mean sleep latency on the Oxford Sleep Resistance Test (MSL_Osler) and (C) number of errors per minute on the OSLER, in 27 treated obstructive sleep apnea subjects. A ceiling effect is observed at 40 min, the scheduled end of the test, in panels A and B

Figure 3)

Epworth Sleepiness Scale scores before and after treatment initiation (by continuous positive pressure airway) in a group of 68 obstructive sleep apnea subjects. A Individual subjects’ scores. Note that most subjects had a decrease in Epworth Sleepiness Scale score with treatment (points to the right of the line). B Group averages before and after treatment initiation, demonstrating a decrease in score with treatment (error bars represent standard error of the mean)

Figure 4)

The Epworth sleepiness scale (ESS) test-retest in a group of 56 untreated obstructive sleep apnea subjects. A Individual subjects’ scores. B Mean scores on the two iterations, with a median of 7.0 months in between (error bar represents standard error of the mean)

Figure 5)

Epworth Sleepiness Scale scores from the self-administered questionnaire (‘subject’) versus scores obtained by the physician during a medical interview (‘physician’). A Scores for the 188 individual subjects. B Average scores for the two modes of administration (error bars represent standard error of the mean). C Average Epworth Sleepiness Scale scores according to method of administration for three different physicians