Researchers Find Increased Sleep Apnea Risk in Study of People with Multiple Sclerosis

People with multiple sclerosis might assume the fatigue they often feel just comes with the territory of their chronic neurological condition.

But a new University of Michigan (U-M) study suggests that a large proportion of people with multiple sclerosis (MS) may have an undiagnosed sleep disorder that is also known to cause fatigue. And that disorder – obstructive sleep apnea – is a treatable condition.

In the latest issue of the Journal of Clinical Sleep Medicine, researchers from the U-M Health System’s Sleep Disorders Center report the results of a study involving 195 patients of the U-M Multiple Sclerosis Center.

In all, 56 percent of the MS patients were found to be at increased risk for obstructive sleep apnea, based on a method of screening for the condition known as the STOP-Bang questionnaire. But most had never received a formal diagnosis of sleep apnea, and less than half of those who had been told they had sleep apnea were using the standard treatment for it.

The authors also found that patients who were more fatigued were more likely to also be at elevated risk for sleep apnea – even after taking into account other factors that might have contributed to feelings of fatigue, such as age, gender, body mass index (BMI), sleep duration, depression and other nighttime symptoms.

“Fatigue is the most common symptom noted in people with MS, and for many it is the most bothersome issue they deal with,” said Ben Thrower, M.D., medical director of the Andrew C. Carlos MS Institute at Shepherd Center in Atlanta. “While many factors may contribute to fatigue in the person with MS, it appears that obstructive sleep apnea (OSA) may be under-recognized as a cause. At the Andrew C. Carlos MS Institute, we have diagnosed OSA with sleep studies in many of our patients.

“Typically, OSA is seen in men more than women, with obesity being a risk, as well,” Dr. Thrower added. “These trends may not hold true in people with MS, however. We have diagnosed OSA in thin young women with MS. Diagnosing and treating OSA is important not only for improving fatigue, but also for the prevention of future health problems that may result from OSA, such as congestive heart failure.”

The U-M research is based on patients’ answers from a sleep questionnaire designed by the study’s authors and four validated instruments designed to assess daytime sleepiness, fatigue severity, insomnia severity and obstructive sleep apnea risk. Medical records also were accessed, with patients’ permission, to examine clinical characteristics that may predict fatigue or obstructive sleep apnea risk.

“We were particularly surprised by the difference between the proportion of patients who carried an established diagnosis of obstructive sleep apnea – 21 percent – and the proportion at risk for obstructive sleep apnea based on their STOP-Bang scores, which was 56 percent,” said the study’s lead author, Tiffany Braley, M.D., M.S. “These findings suggest that OSA may be a highly prevalent and yet under-recognized contributor to fatigue in persons with MS.”

Braley, an assistant professor of neurology and a multiple sclerosis specialist at the U-M Medical School, conducted the study in collaboration with professors Ronald Chervin, M.D., M.S., and Benjamin Segal, M.D. Chervin is the director of the U-M Sleep Disorders Center, and Dr. Segal directs the U-M MS Center.

MS is an immune-mediated disease of the central nervous system that causes inflammation and damage of the brain and spinal cord. In addition to neurological disability, MS patients experience a number of chronic symptoms, the most common of which is fatigue. Fatigue is also one of the most disabling symptoms experienced by people with MS.

Dr. Braley cautioned that the design of this new study does not allow for demonstration of cause and effect – that is, the researchers can’t prove based on survey results that the patients felt more fatigued because they had a high score on a sleep apnea risk survey. But, she said, “The findings should prompt doctors who treat MS patients to consider sleep apnea as a possible contributor to their patients’ fatigue, and recommend appropriate testing and treatment.”

The standard treatment for obstructive sleep apnea, called continuous positive airway pressure, or CPAP, involves a machine and mask device that applies a stream of air to the upper airway to keep it open during sleep.

The patients in the study had an average age of 47 and had lived with MS for an average of 10 years. Two-thirds were female, consistent with the prevalence of MS in the United States, and two-thirds were taking a medication to treat their MS. Three-quarters had the relapsing-remitting form of the condition.

Dr. Braley’s work on this study was funded in part by an American Sleep Medicine Foundation Bridge-to-K grant.

For more information about MS treatment at Shepherd Center’s MS Institute, visit www.shepherd.org/patient-programs/multiple-sclerosis.