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What causes fatigue in people with multiple sclerosis?

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Updated July 10, 2007

Question: What causes fatigue in people with multiple sclerosis?
Fatigue is considered by many to be the worst part of multiple sclerosis, affecting 85 to 95% of those with MS. Indeed, on "bad days" it is unimaginably difficult to even meet one's basic needs, due to overwhelming tiredness that makes everything more difficult. As it turns out, MS-related fatigue is usually the product of several factors working together.
Answer: Fatigue in MS is caused by many factors, which can be grouped into those causing primary fatigue and secondary fatigue.

Primary Fatigue

Primary fatigue is the result of the disease process itself, and is caused by demyelination in the central nervous system.
  • “Lassitude” is an overwhelming tiredness that is not directly related to increased activity.
  • Heat sensitivity fatigue comes from the heat intolerance many of us with MS experience due to hot or humid weather or raising our body temperature through exercise or exertion.
  • There is also something called “short-circuiting” or “localized” fatigue, where affected nerves of individual muscle groups tire with use, such as your legs after walking or your hand after writing.

Secondary Fatigue

Secondary fatigue is not caused directly by the MS itself, but is usually a result of MS symptoms or trying to compensate for them.
  • Sleep disturbances are common in people with MS, due to spasms, depression or anxiety, pain, the frequent need to urinate at night (nocturia) or because of side effects of medications (corticosteroids like Solu-Medrol are notorious for causing sleep disturbances).
  • Exertion causes fatigue in people with MS when they constantly need to compensate for symptoms like spasticity or muscle-weakness, which may make it harder to walk, keep your balance or complete tasks around the house.
  • Some medications also cause fatigue as a side effect, including those taken specifically for MS, including the disease-modifying therapies which are made from beta-interferon (Avonex, Betaseron and Rebif), Tysabri and Novantrone. Fatigue is a side effect of some medications taken for MS symptoms such as spasticity (including baclofen, Valium and Zanaflex) or pain (including Klonopin and Neurontin). Others include medications for high-blood pressure, allergy medications and others containing antihistamines, and anti-anxiety drugs.
  • Depression often causes people to feel overwhelmingly tired. In some people, the fatigue itself causes depression. Some of the medications used to treat depression can also cause fatigue.
  • Lack of proper nutrition also causes swings in blood sugar leading to general tiredness.
  • Infections, such as colds, flu or urinary tract infections can cause fatigue.
  • Lack of physical fitness can greatly contribute to fatigue.

My Experience:

As a long-time sufferer of MS-related fatigue, I think my worst fatigue is usually a combination of many of these factors. On my most challenging days, I’ll experience the crushing, overwhelming fatigue of MS “lassitude” from the minute I get up. I’ll try to self-medicate this with caffeine, which usually means I end up taking a really long nap too close to bedtime. I try to fix that with a tiny sliver of a prescription sleep medication, which leaves me a little drowsy the next day. Of course, during a day like this, the last thing on my mind is exercising. Add to this equation the fact that I don’t feel like cooking, and end up surviving the day eating unhealthy snacks. The icing on the cake is my heat intolerance, which deflates me during any trips outside in hot months unless I take precautions. I have also learned that for me any alcohol greatly contributes to this cycle. This is okay, because by evening on days like this, I am usually too tired to lift a wine glass, anyway.

Sources:

MS in Focus: Fatigue. Volume I. 2003. Multiple Sclerosis International Foundation.

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