The Fatigue Severity Scale (FSS) was designed in 1989 by Doctors Lauren B. Krupp, Nicolas G. LaRocca, Alfred D. Steinberg, and nurse Joanne Muir-Nash. It is a 9-item scale that measures the severity of fatigue and its effect on the participant’s daily activities and lifestyles for people with various different disorders. It was originally created for people with multiple sclerosis or systemic lupus, but now is also used to assess many other patients, such as those with Circadian Rhythm Sleep Disorders (CRSD), cancer rehabilitation, Parkinson’s disease and other neurological rehabilitations, and stroke recovery.

The questionnaire contains nine questions about fatigue, its severity, and its effects on certain activities. The answers are scored on a seven point scale, with 1 being strongly disagree and 7 being strongly agree. Thus, scores can range from 9 – 63, with higher scores indicating higher severity of fatigue.



The assessment is simple to understand and relatively brief, taking about 5-8 minutes to answer. Additionally, there are multiple language translations available to account for language barriers, such as Brazilian-Portuguese, Finnish, German, Norweigen, and Turkish. The FSS is also easy to administer and has been used widely in research for Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), as it is able to measure fatigue as well as the effect of fatigue on certain functions.



Being that it is a self-reported assessment, the test is prone to the unavoidable response biases and other possible factors from such questionnaires. In addition, the FSS could be susceptible to ceiling effects since many ME/CFS patients will score close to or at the maximum score. Consequently, it is not suitable for severe and very severe ME patients.


Overall Reliability

The Fatigue Severity Scale has proved to be a useful tool in aiding diagnosis and treatment of various sleep and related neurological disorders, as long as it is used in conjunction with other diagnostic checks.  It is helpful and generally reliable for exploring the impact and results of a wide range of fatigue related issues and their risks.


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