Stanford Sleepiness Scale

The Stanford Sleepiness Scale was first presented in 1972 by Hoddes and associates. It is one of the oldest subjective sleepiness scales still in use today.

The Stanford Sleepiness Scale is a totally subjective rating subjects where give evaluating how they feel – from 1 to 7. 1 means totally alert (vigilant) and 7 means really struggling to stay awake and dream-like thoughts are occurring. The SSS can be of use in pinpointing the person’s circadian rhythms by tracking a person’s sleepiness and wakefulness throughout the day. Knowledge of personal circadian rhythms could allow shift workers to work during hours in which they are least sleepy/most alert. In addition, administering the test may prevent inappropriate dozing by placing raising awareness of sleepiness in the subject.

While it is still used in sleep studies, the scale’s general applicability suffers from its lack of detail and requires the patient to have some awareness of their fatigue. Criticism of the SSS is that sleepiness is not a unidimensional construct (which the scale implicitly assumes) and that there are equivalent ways of quantifying sleepiness.

The Stanford Sleepiness Scale is convenient, if imprecise and unreliable, and good for repeated queries over the course of a test period or day. It can’t differentiate between people with sleep disorders and healthy people who are just sleepy. However, many doctors use it because it is so easy to use in the office and doesn’t require equipment.

Even simpler is the Karolinska Sleepiness Scale which is just a one-point question of how sleepy a person feels. This is too simple to any statistical validity, but some clinicians employ it, if informally. The vagueness of “excessive daytime sleepiness” prompts some doctors to look for a hook to hang a diagnosis on, and the KSS and SSS fill that need.

Researchers in South Africa developed a scale based on pictorial representation of sleepy people in an effort to reach illiterate or inarticulate people (e.g. children, uneducated).


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