Study objectives: To evaluate the psychometric properties and clinical significance of a new scale for measuring daytime fatigue associated with insomnia: The Flinders Fatigue Scale (FFS).
Methods: The 7-item FFS was used in two separate studies. Study 1 was an on-line validation study involving 1093 volunteers (mean [SD] age = 38.6 [14.7] y, 626 poor sleepers, 467 good sleepers) in a cross-sectional design; Study 2 investigated the clinical sensitivity of the FFS on 113 insomnia patients (mean [SD] age = 48.3 [15.0] y) in response to a 5-week cognitive-behavior therapy for insomnia (CBT-I) program.
Results: The FFS had an internal consistency of 0.91; it comprised a single factor, accounting for 67% of the total variance. Poor sleepers in Study 1 scored significantly higher than good sleepers on the FFS (p < 0.0001). In Study 2, significant reductions in FFS scores were found in response to CBT-I (p < 0.0001). These reductions in fatigue correlated with improvements on subjective sleep parameters (all p < 0.0001). The FFS showed good discriminant validity with the Epworth Sleepiness Scale.
Conclusions: The Flinders Fatigue Scale is a brief, clinically sensitive measure with strong psychometric properties.