Stanford Sleepiness Scale


The Stanford Sleepiness Scale , developed by Dement and colleagues in 1972, is a one-item self-report questionnaire measuring levels of sleepiness throughout the day. The scale, which can be administered in 1–2 minutes, is generally used to track overall alertness at each hour of the day. The scale has been validated for adult populations aged 18 and older. The SSS is used in both research and clinical settings to assess the level of intervention or effectiveness of a specific treatment in order to compare a clients progress.

Reliability and validity

Reliability

refers to whether the scores are reproducible. Unless otherwise specified, the reliability scores and values come from studies done with a United States population sample.
CriterionRating Explanation with references
NormsNot applicableMean and standard deviation do not exist because the SSS is a single item questionnaire.
Internal consistency Not applicableSSS only has one question
Inter-rater reliabilityNot applicableDesigned originally as a self-report scale
Test-retest reliability Goodr =.88
RepeatabilityNot publishedNo published studies formally checking repeatability

Validity

describes the evidence that an assessment tool measures what it was supposed to measure. Unless otherwise specified, the reliability scores and values come from studies done with a United States population sample.
CriterionRating Explanation with references
Content validityAdequateFollows characteristics of alertness, but sleepiness is not unidimensional and difficult to quantify
Construct validity GoodShows convergent validity with other symptom scales such as ESS and Karolinska Sleepiness Scale, prediction of performance after sleep deprivation
Discriminative validityAdequateStudies do not report AUCs, some mention overlap between sleepiness, physical tiredness, and depression
Validity generalizationGoodEvidence supports use in a variety of research and clinical settings, but only in persons of 18 years and older
Treatment sensitivityNot applicableSSS is not intended for use as a measure of outcome
Clinical utilityAdequateFree, brief, easy administration

Development and history

The SSS was developed to measure subjective sleepiness in research and clinical settings. Other instruments measuring sleepiness tend to examine the general experience of sleepiness over the course of a day, but the SSS met a need for a scale measuring sleepiness in specific moments of time. Because it can be used to evaluate specific moments, the scale can be used repeatedly at different time intervals in a research study or for treatment intervention.

Use in other populations

Since the development of the SSS there have been other more specific and more recently developed sleepiness rating scales such as the Epworth Sleepiness Scale which are more commonly used in other populations. Due to the fact that it has only been translated into English, it is not significantly used in other populations.

Limitations

The primary limitations of the Stanford Sleepiness Scale is that it is a self-report measure, because of this, levels of sleepiness may be over or under reported based on personal biases. The SSS is free to the general public and can be found in many forms online.