1026 Validation of the Situational Sleepiness Scale

Introduction

The Epworth Sleepiness Scale (ESS) is the gold standard measure subjective daytime sleepiness. Since the inception of the ESS 25 years ago, modern life has evolved considerably and the situations posed by the ESS have become dated. This interim analysis introduces the Situational Sleepiness Scale (SSS) which focuses on common activities occurring in the modern world.

Methods

A group of sleep physicians and staff between Stanford and the UK Biobank developed the questionnaire. An initial set of questions were distributed to subjects, and through multiple iterations of subject feedback and subsequent revision, were refined into its current form of eleven situations. To explore further the scale as a replacement for the ESS, the SSS and the eight situation ESS were given in tandem to patients and visitors of the Stanford Sleep Clinic.

Results

A correlation coefficient between the ESS and SSS was run on 121 completed questionnaires. Our result to date indicates a strong correlation between both scales (R2=0.74, p<.0001). The mean score for the SSS was 7.74 and 7.36 for the ESS. The standard deviation for the SSS was 5.11 compared to 4.74 for the ESS. A test of variance produced a value of 25.9 for the SSS and 22.3 for the ESS. Thirty-four subjects scored ≥ 10 in this sample using the ESS and 26 of these subjects had a value ≥ 10 for the SSS. Most of the subjects who scored ≥ 10 on the ESS scored ≥ 10 on the SSS and vice versa suggesting that a similar cutoff could be used for defining daytime sleepiness on the SSS.

Conclusion

In this interim analysis, we found the Situational Sleepiness Scale to be easily administered and to correlate well with the ESS. In future studies we will examine consistency of scores across item, stability over time/ repeatability, and explore psychometric properties. Additional studies aiming at gathering several hundred subjects with various diagnoses are ongoing. As the SSS goes up to 33, but has a similar cutoff of ten on the correlation, we believe the SSS could be more discriminative than the ESS for very sleepy patients such as narcoleptics.

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