Patients with multiple sclerosis might assume that the tiredness they often feel comes with the territory of their chronic neurological condition. But that fatigue could actually be a result of an undiagnosed sleep disorder that is easily treated.
A large portion of MS patients in a new study were 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.
Published in the Journal of Clinical Sleep Medicine, the study also shows that patients who are more fatigued are 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.
The research is based on patients’ answers from a sleep questionnaire and 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,” says Tiffany Braley, assistant professor of neurology at the University of Michigan. “These findings suggest that OSA may be a highly prevalent and yet under-recognized contributor to fatigue in persons with MS.”
Braley conducted the study in collaboration with Ronald Chervin, professor of sleep medicine, and Benjamin Segal, professor of neurology.
Fatigue and multiple sclerosis
Multiple sclerosis 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 suffer from a number of chronic symptoms, the most common of which is fatigue. Fatigue is also one of the most disabling symptoms experienced by MS patients.
The researchers caution that the design of the new study doesn’t 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, “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,” Braley says.
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 US, and two-thirds were taking a medication to treat their MS. Three-quarters had the relapsing-remitting form of the disease.
The work was funded in part by an American Sleep Medicine Foundation Bridge-to-K grant.
Source: University of Michigan