Fatigue Measurement
Fatigue is generally measured by objective methods, such as performing tasks repeatedly and measuring the decline in responses, or by subjective measures, like self-reports where a participant describes or rates their fatigue (Onate-Figuérez et al. 2023). The studies included in this systematic review measure fatigue using self-reports, with the Fatigue Severity Scale (FSS) being the most common measure. The FSS is a 9-item self-report questionnaire that evaluates the severity of fatigue and its impact on lifestyle and activities in three domains: physical, social, and cognitive effects of fatigue (Curtis et al. 2015; Hewlett et al. 2011). It has high validity and reliability (Cronbach’s α=0.89, intraclass correlation coefficient, 0.84; 95% confidence interval [CI] 0.74-0.90) for evaluating fatigue in people with SCI (Anton et al. 2008). More information about the FSS is available on the SCIRE Professional webpage: Fatigue Severity Scale.
Other less commonly used measures included the Chalder Fatigue Scale (CFS), the Multi-Dimensional Fatigue Inventory (MFI-20), the Modified Fatigue Impact Scale (MFIS), the PROMIS Short Form v1.0 Fatigue 8a, and the Fatigue Assessment Scale (FAS). The CFS is a self-rated fatigue scale that provides an overall indicator of chronic fatigue, as well as domains of mental and physical fatigue (Chalder et al. 1993). The MFI-20 covers five dimensions: General Fatigue, Physical Fatigue, Mental Fatigue, Reduced Motivation, and Reduced Activity (Hagelin et al. 2007; Smets et al. 1995). The MFIS is a 21-item shortened version of the 40-item Fatigue Impact scale that examines the perceived impact of fatigue in cognitive functioning, physical functioning and psychosocial functioning (Fisk et al. 1994; Shem et al. 2016; Wong et al. 2023). The PROMIS Short Form v1.0 Fatigue 8a evaluates fatigue based on its frequency, duration, and intensity, as well as its impact on physical, mental, and social activities (Cella et al. 2010; Wong et al. 2023). Lastly, the FAS is a 10-item scale evaluating symptoms of chronic fatigue which treats fatigue as a unidimensional construct and does not separate its measurement into different factors (Shahid et al. 2012).
Although different outcome measures for fatigue have been used in SCI research, the FSS is the only (and most used) outcome measure that has been validated in people with SCI. In addition, the 7-item version of the FSS has been recently recommended as a primary outcome measure in stroke research (English et al. 2023).
