MS, fatigue and sleep disorders: putting the matter to bed

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. According to the Canadian Community Health Survey from 2002, more than 3 million Canadians, or 10-15% of the population, experience insomnia. Among people with MS, that proportion is believed to be higher, with some estimates of prevalence exceeding 30%. Whether MS is part of the cause of insomnia, or if it exists as a separate condition in people with MS, remains unclear. Treatment strategies for insomnia can include a combination of discussing lifestyle changes to improve sleep hygiene and, if necessary, pharmacological intervention.

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. OSAH affects an estimated 3% of Canadians, and recent data reveals that an estimated 58% of people with MS are affected with this condition. Dr. Daria Trojan and colleagues at the Montreal Neurological Institute demonstrated in an MS Society-funded study that OSAH is the most frequent sleep disorder found in people with MS, and went on to show that treating OSAH in those people may lead to improved fatigue. I talk about this in more detail further along in the post.

Restless legs syndrome (RLS): People with RLS report uncomfortable and unpleasant sensations in the legs that occur primarily at night, resulting in an uncontrollable urge to move their legs in order to relieve the discomfort. RLS is often accompanied by a condition called periodic limb movements of sleep (PLMS), in which people experience severe and involuntarily jerking of the limbs during sleep, causing sleep fragmentation and daytime sleepiness. Like many other sleep disorders, RLS appears to be significantly more common in people living with MS compared to the general population, and the associated sensory and motor impairments  – including involuntary limb movements during sleep and feelings of “insects crawling up the legs” during waking – can seriously aggravate other MS symptoms.

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. Considerable evidence suggests that an autoimmune response may be the culprit for this loss of hypocretin (although this issue is still a matter of debate). Thus since MS, and to a lesser extent narcolepsy, are considered autoimmune disorders, understanding the disease mechanisms that underlie narcolepsy may shed light on potential therapies for MS.

Sleep disorders: at the root of fatigue in MS?

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.

A landmark study by a team at McGill University, published in Multiple Sclerosis Journal in 2012 and funded in part by the MS Society, demonstrated for the first time that measures of fatigue were significantly improved in people with MS whose sleep disorders were successfully treated, compared to those whose sleep disorders went untreated or who did not present with any sleep disorders. The most remarkable improvement was seen in patients with OSAH, presumably because OSAH was the most common sleep disorder among the participants and had one of the strongest associations with severe fatigue. These findings were confirmed by a German research group, whose article published last year in Clinical Neurology and Neurosurgery also showed that clinical treatment of such sleep disturbances as insomnia, OSAH and RLS may improve fatigue in MS.

A more recent study that came out of University of California Davis and was published in the Journal of Clinical Sleep Medicine last month was perhaps the largest single investigation of sleep disorders in people with MS. This survey-based population study of 2,375 individuals diagnosed with MS revealed that a high proportion of respondents screened positive for one or more sleep disorder – including insomnia, OSAH or RLS – yet a vast majority were undiagnosed by their clinicians. This discovery points to an important gap in our recognition of the presence and impact of sleep disorders in people living with MS. It is encouraging to see that important studies such as these have unlocked promising avenues for understanding what factors cause fatigue alongside other MS symptoms, and offer hope to people with MS that there are ways to finally put their fatigue to bed.

What can you do?

I have heard from many people living with MS that fatigue is a common part of their daily lives, which imposes on them serious challenges such as those I mentioned at the beginning of the post. Fortunately, there is hope for managing fatigue in people with MS by tackling potential underlying sleep disorders. If you have MS and feel tired and poorly rested throughout the day, your family doctor can help to find the right treatment plan for you. He or she may refer you to a sleep clinic, where you can participate in a sleep consult and have the opportunity to talk to a specialist about issues you’ve encountered with sleep.

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. Do you or someone you know with MS have problems falling asleep or experience any of the other sleep problems listed above? Let me know in the comments section below!

Categories Research

National vice-president, research, past MS researcher, and PhD in Cellular and Molecular Medicine from University of Ottawa. Leads the MS Society's research program to find the cure for MS and improve the quality of life for people affected by the disease.

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