Validation of the fatigue severity scale in a Swiss cohort

Sleep. 2008 Nov;31(11):1601-7. doi: 10.1093/sleep/31.11.1601.


Background: Fatigue is highly prevalent and has a negative impact on quality of life and performance in a variety of disorders. The 9-item Fatigue Severity Scale (FSS) is one of the most commonly used self-report questionnaires to measure fatigue, but has only been validated in small sample-sized studies and in single disorders.

Objective: To validate the FSS in healthy subjects and different disorders known to be commonly associated with fatigue.

Material and methods: The FSS was administered to 454 healthy subjects, 188 patients with multiple sclerosis (MS), 235 patients with recent ischemic stroke, and 429 patients with sleep-wake disorders including narcolepsy with cataplexy (n=22), restless legs syndrome (RLS) (n=79), sleep apnea (n=108), insomnia (n=62), parasomnia (n=25), excessive daytime sleepiness/hypersomnia of other origin (n=84, and other sleep-wake disorders (n=49.

Results: FSS scores were 4.66 +/- 1.64 (mean +/- SD) in patients with MS, 3.90 +/- 1.85 in patients after ischemic stroke, and 4.34 +/- 1.64 in patients with sleep-wake disorders. Compared to patients, values were significantly lower in healthy subjects (3.00 +/- 1.08, P < 0.01). Scores did not correlate with gender, age, or education. Item analysis showed an excellent internal consistency and reliability (Cronbach alpha = 0.93). Test-retest variability was assessed in 104 healthy subjects, showing stable values over time (2.94 +/- 0.90 vs. 2.90 +/- 0.74; P = 0.27).

Conclusions: This first validation of a fatigue scale in a large sample size demonstrates that the FSS is a simple and reliable instrument to assess and quantify fatigue for clinical and research purposes.

Publication types

  • Validation Study

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Cohort Studies
  • Disorders of Excessive Somnolence / epidemiology
  • Fatigue / diagnosis*
  • Fatigue / epidemiology*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Multiple Sclerosis / epidemiology
  • Myocardial Ischemia / epidemiology
  • Prevalence
  • Quality of Life / psychology*
  • Severity of Illness Index
  • Sleep Disorders, Circadian Rhythm / epidemiology
  • Surveys and Questionnaires*
  • Switzerland / epidemiology
  • Young Adult