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a woman melting into a sofa due to fatigue

How Is MS Fatigue Assessed?

Fatigue is one of the most common symptoms of multiple sclerosis (MS). Almost 4 out of every 5 people with MS experience this extreme tiredness. Over half describe it as their worst symptom. A person with MS may feel very tired every day and have felt that way for years.1

MS fatigue affects your ability to work, socialize, and enjoy leisure time. It also affects cognitive function, which includes memory, perception, and judgment. People with MS who have fatigue also may need to see healthcare specialists more often.2

What is primary MS fatigue?

There are 2 types of MS fatigue: primary and secondary. Primary fatigue is specific to having an MS diagnosis. It is not clear what causes MS primary fatigue. It may be related to problems with the immune system or neuroendocrine system. The neuroendocrine system involves both the nervous system and endocrine system, which controls the hormones in your body.1

An imbalance of dopamine may also cause fatigue. Dopamine is a chemical that sends messages between nerve cells in your brain and your body. This type of chemical is called a neurotransmitter. Other changes in the brain caused by MS are another possible cause of primary fatigue.3-5

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Secondary MS fatigue

Secondary fatigue has to do with factors related to MS but not the condition itself. Secondary fatigue can have several causes, including:5

  • Drug side effects
  • Sleep disorders
  • Inactivity
  • Mental health issues

How is MS fatigue measured by a doctor?

There is no specific test for MS fatigue. When you visit your doctor, they will ask you to describe your symptoms. They may do some blood work to rule out other conditions. They may test for a urinary tract infection, liver or kidney disease, or an underactive thyroid (hypothyroidism).2

To determine whether your fatigue is primary or secondary, your doctor will look for signs that your MS is progressing. They will also review your medicines to see if any may be making you tired. And they may give you a questionnaire about your fatigue.2

The Modified Fatigue Impact Scale

One questionnaire doctors use is the Modified Fatigue Impact Scale (MFIS). The MFIS is a written questionnaire based on interviews with people who have MS and fatigue.6

The full-length version has 21 questions, and the shorter version has 5 questions. You will read statements about MS fatigue and circle the answer that best describes how it has affected your life in the past 4 weeks. If you need help marking your answers, you can give them verbally. The doctor will then mark your answers for you.6

The MFIS asks about how fatigue has affected your body, emotions, and thinking. Your answers place you on a scale from 0 to 4. The higher the number, the more troubling the fatigue. Some statements on the MFIS include:6

  • I have been less alert.
  • I have been clumsy and uncoordinated.
  • I have been less motivated to participate in social activities.
  • My muscles have felt weak.

The Fatigue Severity Scale

Another commonly used questionnaire is the Fatigue Severity Scale (FSS). The FSS has 9 questions that measure how fatigue affects different areas of your life. These areas include:7

  • Motivation
  • Exercise
  • Physical functioning
  • Duties and obligations
  • Work
  • Family
  • Social life

The FSS uses a 7-point scale, ranging from "strongly agree" to "strongly disagree."7

Dealing with MS fatigue

While there is no cure for MS fatigue, there are ways of managing it. Your doctor may suggest some medicines known to ease fatigue. They may also recommend:2,8

  • Lifestyle changes like doing light exercise
  • Cooling devices, which may help when fatigue is made worse by hot weather
  • Keeping a consistent sleep routine
  • Eating a diet high in fruits and vegetables and low in fat and processed foods

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