Sleep disturbances, including obstructive sleep apnea, may be contributing to daytime fatigue in a large proportion of people with multiple sclerosis, based on the results of an observational study of 195 MS patients without additional neurologic disorders, such as Parkinson’s disease or stroke, which could independently increase OSA risk.
Obstructive sleep apnea – a common and treatable disorder – is likely underrecognized in this patient group as aggravating or causing fatigue, according to the investigators, led by Dr. Tiffany J. Braley of the multiple sclerosis center at the University of Michigan, Ann Arbor.
More than half of all subjects, they found, had evidence of an elevated risk for OSA, and a fifth had a prior diagnosis of OSA. OSA risk emerged as a significant predictor of fatigue severity after adjusting for confounding factors.
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Obstructive sleep apnea is an oft overlooked contributor to daytime fatigue in people with multiple sclerosis, says Dr. Tiffany J. Braley.
In the study, Dr. Braley and her colleagues administered a validated OSA scoring tool called STOP-Bang to all participants to collect information related to snoring, observed apnea, fatigue, blood pressure, body mass index, age, neck circumference, and gender. They also conducted an extensive sleep questionnaire and administrated validated fatigue, insomnia, and sleepiness scoring tools. The researchers consulted patient medical records to assess information on disease severity, depression, and disability (J. Clin. Sleep Med. 2014;10:155-62).
The patients had a mean age of 47 years, and 66% were female. Overall, 41 (21%) had a prior OSA diagnosis, and 110 (56%) had a STOP-Bang score of 3 or greater, which is indicative of elevated OSA risk. A STOP-Bang score of 3 or more functioned as a significant predictor of higher fatigue scores (P = .01). More nocturnal symptoms and higher disability levels also predicted fatigue.
The proportion of subjects at risk of OSA in the study was at the high end of previous estimates in MS patients, Dr. Braley and her colleagues wrote, but they were surprised to find relatively few OSA diagnoses while more than half the cohort had elevated risk, suggesting that the findings may reflect "suboptimal OSA diagnosis patterns."
"Underrecognition of other symptoms that may signal OSA – such as fatigue – may also explain the discrepancy we found, particularly in patients who suffer disproportionately from fatigue because of a comorbid condition (MS)," they wrote.
The investigators noted that the cross-sectional, observational design of their study meant that they could not establish OSA as causing fatigue in the cohort, and acknowledged that sleep disturbance related to other causes could be contributing. In addition, they cautioned, this was a single-site study, and the findings could reflect characteristics of patients referred to the investigators’ clinic.
Nonetheless, they wrote, clinicians caring for patients with MS "should maintain a low threshold" to screen for OSA, and make efforts to identify any nocturnal symptoms that could affect patients’ sleep quality and contribute to daytime fatigue.
The investigators estimated that as much as 40% of fatigue in MS could be eliminated through better diagnosis and successful treatment of patients with OSA.
The study had no outside funding. Dr. Braley and her two coauthors have received research support from companies marketing multiple sclerosis drugs or OSA therapies and in some instances received compensation for activities with such companies. Dr. Braley and coauthors have been named in patents or provisional patents for sleep apnea treatments held by the University of Michigan.