Sleep Related Questionnaires

Stanford Sleepiness Scale (SSS)

Name of questionnaire Stanford Sleepiness Scale (SSS)
Type of questionnaire-description Self-rating scale which evaluates sleepiness at a certain point in time. Respondents select one of seven statements best representing their perceived sleepiness
Number of items 1
Number of domains/categories 1
Name of categories/domains   Degree of sleepiness
Scaling of items Seven –point Likert-type scale has descriptors ranging from “feeling active, vital alert, or wide awake” (score = 1) to “no longer fighting sleep, sleep onset soon
and having dream-like thoughts” (score = 7)
Scoring available: with permission or free Free
Scoring test-retest reliability 0.88
Scoring Internal consistency Not available
Validity Validity of mean SSS using the Wilkinson addition and vigilance tests was reported at correlation of 0.68
Language English 
Patient populations in whom questionnaire has been validated Adults
Translations in other languages (if yes, then list the languages) Not applicable
Developer name E. Hoddes, V. Zarcone, H. Smythe, R. Phillips, W. C. Dement
Developer contact information William C. Dement, M.D., Ph.D.
Professor of Psychiatry and Sleep Medicine
Department of Psychiatry and Behavioral Sciences
Stanford University School of Medicine
1050A Arastradero Rd.
Palo Alto, CA 94304
Ph: 650-723-6320
Fax: 650-723-8134
Availability of questionnaire: Freely available
Limitations Questionable reliability in chronic sleep deprivation, cumulative  partial sleep deprivation and narcoleptics  
Link to the questionnaire (if available)

Other comments It can be administered many times per day which is useful over the course of a study (e.g., treatment intervention).
Correlates with standard measures of performance and reflects the effects of sleep loss.  

Original publication:

  1. Hoddes E, Zarcone V, Smythe H, Phillips R, Dement WC. Quantification of sleepiness: a new approach. Psychophysiology. 1973 Jul;10(4):431-6.

 Validity and reliability in different populations:

  1. Herscovitch J, Broughton R. Sensitivity of the stanford sleepiness scale to the effects of cumulative partial sleep deprivation and recovery oversleeping. Sleep. 1981;4(1):83-91.
  2. MacLean AW, Fekken GC, Saskin P, Knowles JB. Psychometric evaluation of the Stanford Sleepiness Scale. J Sleep Res. 1992 Mar;1(1):35-39.
  3. Miró E, Cano-Lozano MC, Buela-Casal G. Electrodermal activity during total sleep deprivation and its relationship with other activation and performance measures. J Sleep Res. 2002 Jun;11(2):105-12.
Updated by

Marie-Anne Melone

Last update September 2022