Fatigue is a common, often debilitating symptom that affects nearly 80 percent of people with multiple sclerosis (MS). Whether it’s chronic or due to a flare-up, the National MS Society (NMSS) says fatigue “can significantly interfere with a person's ability to function at home and at work.” Extreme fatigue is also a common symptom of obstructive sleep apnea (OSA), a disorder that afflicts nearly 18 million Americans.

Dr. Tiffany J. Braley, an assistant professor of neurology at the University of Michigan Multiple Sclerosis and Sleep Centers, was curious about whether OSA plays a role in MS-related fatigue. In her team's latest study, 195 patients from the university’s MS clinic were given questionnaires designed to measure OSA risk, OSA diagnoses, and fatigue.

“The inspiration behind this stems from personal experiences with my patients,” Braley said in an interview with Healthline. “I have encountered many MS patients in my practice whose fatigue improved when their underlying sleep disorders, particularly OSA, were finally diagnosed and treated."

The study took into account other conditions often seen in people with MS, such as depression, which can also affect sleep and fatigue. The patients answered questions about their quality of sleep, the quality of their waking hours, and whether they took anything to help them either sleep or stay awake.

Braley and her team used a validated scale to determine the patients' risk of OSA (the STOP-Bang Questionnaire), which measures snoring, tiredness, apnea, blood pressure, body mass index, age, neck circumference, and gender.

They found that one fifth of the MS patients surveyed had definite OSA and more than half were at an increased risk of developing the sleep disorder. Most had never been formally diagnosed with the condition, and among those who had, less than half were receiving treatment for it.

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What Is Obstructive Sleep Apnea?

According to The National Sleep Foundation, OSA is a disorder in which patients stop breathing briefly but repeatedly throughout the night.

OSA is characterized by a pause in breathing while asleep—sometimes for as long as ten seconds—when the muscles of the throat relax and cause the airway to collapse. This can cause disrupted sleep and oxygen deprivation to the brain, which can lead to heart disease and high blood pressure.

Besides fatigue, other symptoms of OSA include chronic snoring, high blood pressure, sleeplessness, irritability, trouble concentrating, and falling asleep while at work or driving.

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Sick and Tired of Being Sick and Tired

If you suspect your MS fatigue may be compounded by OSA, your first step should be to create a sleep journal. Document how well you slept the night before, what your daytime symptoms were the next day, and if you took anything to either fall sleep or stay awake. Ask your sleep partner to tell you if you snore loudly or pause while breathing. 

Then speak to your neurologist or primary care doctor who can refer you to a sleep specialist. OSA is typically diagnosed with a sleep study and usually involves an overnight stay at a sleep center. You may also need to fill out questionnaires designed to draw out the details of your sleeping habits.

The treatment of choice for OSA is a continuous positive airway pressure (CPAP) machine. The CPAP machine has a mask that fits over your nose and mouth, and it gently blows air into your airway to keep it open while you sleep. According to the National Sleep Foundation, CPAP treatment is highly effective.

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Could MS Cause Sleep Apnea?

“That is a good question,” Braley said. Her study did not look at MS-specific causes for OSA, but her group published an earlier study that addressed this possibility. The results suggested that “patients who have more MS-related damage to their brainstem (which controls airway opening and breathing) may be at higher risk for OSA, but additional studies are necessary to confirm this.”

MS is a disease that affects the nervous system, which in turn controls muscle movements. Dysphagia, or trouble swallowing, is a symptom experienced by many with MS and involves the muscles of the throat, which are controlled by the brainstem. If these same muscles relax during sleep, it could cause apnea, but for now, that is just speculation.

Although there is evidence to suggest a link between sleep disturbances and MS fatigue, a cause-and-effect relationship has not been established. “Our study has some limitations,” the authors concede. It’s possible that the researchers saw such a high prevalence of OSA in their MS patients because the center specializes in sleep disorders as well as MS.

Whatever the connection, if you suffer from fatigue, it's a good idea to have your sleep quality checked by a doctor.