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MS, Fatigue & Sleep Disorders by Dr. Karen Lee

November 8, 2016

Fatigue is perhaps the most prevalent and disabling symptom experienced by persons affected by MS.  An overpowering feeling of fatigue can severely affect daily functioning and, particularly when compounded by other symptoms of MS, impairs performance at work or school and affects one’s interactions with friends and family. While the cause of fatigue in MS is still unknown, one hypothesis that is gaining ground among scientists and clinicians alike is that underlying sleep disorders may play a larger role than previously thought. Promising data out there suggests that identifying and treating sleep disorders can go a long way towards alleviating fatigue and improving quality of life in people with MS. This is good news, since fatigue is generally resistant to the frontline treatments that are the mainstay of MS symptom management.  In this post, I’ll talk about some of the most common sleep disorders identified in people living with MS, discuss the evidence linking sleep disorders with fatigue, and identify potential strategies that people with MS can pursue to manage fatigue.

Some common sleep disorders

Disorders affecting sleep and waking are numerous and complex; however, one feature they almost invariably share in common is a reduction in sleep quality at night along with an increase in sleepiness during the day. Here are some of the most common sleep disorders, found both in people with MS and among the general population.

Insomnia: Certainly the most widespread and well-known sleep disorder, insomnia is defined as difficulty in falling asleep or staying asleep, despite adequate opportunity. 30% of the MS population is said to experience this disorder.

Obstructive sleep apnea hypopnea (OSAH) syndrome: A sleep-related breathing disorder, OSAH syndrome is characterized by interruptions in breathing that occur during the night as a result of a collapse of the upper airway. Each interruption can persist for up to 30 seconds, until the brain detects reduced oxygen levels in the blood and triggers a brief awakening to restore normal breathing. Although someone with OSAH can experience hundreds of these breathing interruptions and arousals in a night, they often don’t realize their sleep has been fragmented, despite feeling sleepy and fatigued during the day. In addition to causing poor quality sleep, OSAH has been linked with other serious illnesses, such as heart disease and diabetes.

Narcolepsy: Narcolepsy is a disorder distinguished by instability in the sleep-wake cycle. The symptoms of narcolepsy are several-fold, the most common of which is excessive daytime sleepiness. However, one of the most striking features is a symptom called cataplexy, in which positive emotions, such as laughter, can bring about a sudden bout of muscle weakness and loss of voluntary muscle control. You may have heard the expression that laughter can make you feel “weak in the knees”; now imagine that weakness magnified to the point of physical collapse! Narcolepsy is believed to be caused by the loss of a certain molecule which promotes waking – called hypocretin – in the brain. 

There is an increasing awareness among the scientific community that sleep disorders may be a vital contributing factor to the debilitating fatigue experienced by individuals with MS. This is important because many tried-and-tested strategies for managing sleep disorders in the clinician’s toolkit can potentially allow people with MS to feel less tired and more refreshed and alert, leading to improved daily functioning. We’ll take a look at a few studies that have offered crucial insights into the links between MS, fatigue and sleep disorders.

What can you do?

One potential approach is participation in a sleep study, which involves spending the night in the clinic while your brain activity, heart rate, breathing, eye movements and muscle activity are monitored using a technique called polysomnography. This painless technique can uncover a range of sleep disorders that a person may otherwise be completely unaware of (after all, it’s difficult to notice symptoms when you’re asleep and, hence, unconscious!). In contrast, a variety of daytime tests are used to gauge levels of sleepiness and alertness during the day.  These and other tools will provide your sleep specialist(s) with important information for diagnosing and treating any underlying sleep disorders.

Researchers note that identifying the symptoms associated with sleep disorders as soon as possible will increase the likelihood of overcoming fatigue and improving quality of life, while decreasing the risk of developing other potentially serious illnesses that are linked to sleep disorders. As more evidence on this topic surfaces, the research and medical communities will be able to uncover the role sleep disorders play in the onset and severity of fatigue among people with MS, as well as determine if MS is directly linked to the development of sleep disorders. This insight can potentially lead to new treatments that reduce fatigue and enable people living with MS to undertake daily activities and participate fully within the community.