Validation of the Fatigue Severity Scale in a Swiss Cohort

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 α = 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.

Citation:

Valko PO; Bassetti CL; Bloch KE; Held U; Baumann CR. Validation of the fatigue severity scale in a swiss cohort. SLEEP 2008;31(11):1601–1607.