Sleep & the Science of Pain

Assessing Fibromyalgia as a Co-Morbidity of Sleep Apnea

If asked, knowledgeable respiratory providers and clinicians can tick off the co-morbidities associated with sleep apnea: hypertension, congestive heart failure, diabetes, obesity. But chronic pain conditions, like fibromyalgia, probably won’t make the list. In recent studies, however, researchers have started to rethink the role of sleep in the management of fibromyalgia.

“Sleep is key to fibromyalgia,” says Dr. Patrick Wood, senior medical adviser with the National Fibromyalgia Association and chief medical officer at Angler Biomedical Technologies, Rockville, Md. “Almost universally, patients report problems with insomnia, whether it’s early or late insomnia, and non-refreshing sleep.”

The link between fibromyalgia and sleep dates back to a 1975 study by Dr. Harvey Moldofsky, who found a high incidence of alpha-delta sleep in fibromyalgia patients — or the intrusion of alpha waves (arousal pattern) into restorative sleep. Only recently have researchers begun to explore the role of sleep apnea in fibromyalgia.

Classifying Chronic Pain
Fibromyalgia is defined as chronic widespread pain of three months duration that is present above and below the waist, on the right and left side and in an axial distribution, i.e. the neck, chest wall, back and hips. In addition, patients experience tenderness or pain in at least 11 of 18 specified tender points when pressure is applied.

Rheumatologists first defined the condition because the pathology was believed to be muscle pain, Wood says. “In the last three decades, and increasingly in the last 10 years, we’ve pretty much determined that it’s not at all a muscle problem in the way we traditionally conceive of muscle problems,” he says. “It’s more a problem of the central nervous system.”

The condition is still one of the most common diagnoses in rheumatology clinics, though Wood says anyone who can perform a physical examination and is clinically qualified can diagnose fibromyalgia. “Certainly any primary care provider is going to see lots of fibromyalgia — whether or not they recognize it for being what it is, is another concern.”

In fact, calling fibromyalgia a controversial disease would be an understatement. For several years, physicians did not believe it was a real condition.

“The controversy around fibromyalgia stems, in a large part, from the lack of readily available objectives of abnormalities,” Wood explains. “There’s nothing in the blood work that determines if you have fibromyalgia. There’s nothing that’s readily detectable on standard medical imaging, like X-rays or even MRIs or CTs.”

Instead physicians must use other means, such as testing the cerebral spinal fluid (CSF), which will typically reveal an imbalance between chemicals that would show a high excitatory content and low inhibitory or painkilling content, Wood says. The CSF in fibromyalgia patients also has excessive endorphins.

So, what causes fibromyalgia?

Evidence points to an association to trauma by illness, injury or stress. Patients with chronic inflammatory disorders, like rheumatoid arthritis or lupus, can develop fibromyalgia, Wood says, and a predisposition has been identified among people with stressful life events, such as childhood abuse.

The National Fibromyalgia Association estimates prevalence at 3-6 percent of the population, with a higher incidence among women. Symptoms in addition to pain can include chronic fatigue, cognitive dysfunction, anxiety, depression, restless legs syndrome, irritable bowl syndrome, migraines and sleep disturbances.

While only one drug has earned FDA approval for the treatment of fibromyalgia — Lyrica or pregabalin — traditionally, antidepressants, specifically serotonin norepinephrine reuptake inhibitors, are prescribed. Also dopamine agonists, such as those used to treat Parkinson’s disease and restless legs syndrome, have been used.

“A good way to sort of encapsulate fibromyalgia, something I like to say, is to change the way the brain and spinal cord ‘listen to the body,’ ” Wood says.

Lifestyle management, such as continued aerobic fitness, good sleep hygiene and counseling or cognitive behavioral therapy, are recommended, and pain medications are often prescribed, though opioids may not be the best choice, Wood says.

The Sleep Profile
Studies suggest a connection between fibromyalgia and upper airway resistance syndrome (UARS), which is a variant of obstructive sleep apnea characterized by the partial collapse of the airway resulting in increased respiratory effort during inspiration. UARS is not associated with actual apneas or hypopneas or cessation of breathing. Rather, the condition shows brief, frequent arousals and a slightly abnormal breathing pattern, which improves with the use of CPAP.

Increasingly, studies also are showing a higher prevalence of obstructive sleep apnea, especially among males with fibromyalgia.
“If we go back to the proposition that fibromyalgia is somehow related to stress, you’d appreciate that upper airway resistance and oxygen desaturation at night represent physiological stressors,” Wood says. “As good as the body is at doing what it does, it’s a bit dumb. The body doesn’t know the difference between ‘somebody’s trying to choke me to death at night’ and ‘my palate’s simply flopped over my larynx.’ They both come across the same way to the autonomic nervous system.”

Wood says sleep apnea patients typically exhibit dysautonomia, characterized by sympathetic hyperactivity. What’s also interesting is that fibromyalgia patients also exhibit dysautonomia. “I think, in fact, a lot of the symptoms, maybe even the pain in some cases, is related to dysautonomia, what I would call a dysautonomia sick syndrome,” he says.

Fibromyalgia patients do not necessarily fit the typical OSA profile, however. “My clinical experience … is that a lot of the typical indicators for sleep apnea — obesity, neck girth, things like that — you’re not necessarily going to find in fibromyalgia patients,” Wood says. In fact, fibromyalgia patients with obstructive sleep apnea might be slim with a low BMI.

While there isn’t a lot of evidence to support the existence of central sleep apnea in fibromyalgia patients, some pain medications, such as opioids, can cause central sleep apnea, says Dr. R. Robert Auger, Mayo Center for Sleep Medicine, Rochester, Minn.

Stepping Up Sleep Studies
Though the study of sleep and fibromyalgia is in its infancy, Wood says that clinicians who work with fibromyalgia patients should have a low threshold for sleep screening.

“Certainly, when somebody in my clinic is talking about excessive daytime sleepiness, cognitive dysfunction, I start thinking polysomnography,” he says.

One of Wood’s colleagues screens every fibromyalgia patient for OSA. While that strategy may be aggressive for the majority of physicians, Wood says clinicians must “develop a greater index of suspicion for the existence of sleep problems.”

In fact, screening for sleep might have an impact on fibromyalgia symptoms. Auger says that research has shown that poor sleep quality or disrupted sleep can affect a person’s tolerance and response to pain. “Most of the people get referred here (Mayo Center for Sleep Medicine) in that context,” he says. “They have chronic pain, for example, fibromyalgia, and so they are trying to determine whether improving their sleep will not necessarily cure that complaint, but maybe make it more tolerable or maybe make their pain less frequent or intense. There is some research to support that if you can improve the quality of their (patients’) sleep that pain complaints will improve.”

Auger also says that treating sleep apnea should alleviate, at least in theory, symptoms of fatigue.

In fact, a study in the November 2007 Rheumatology International journal showed a clinical benefit to fibromyalgia patients undergoing CPAP treatment, though the findings did not indicate whether or not CPAP helped to reduce pain. More studies are needed to show if treating sleep can impact pain reduction.

Still, “fibromyalgia patients as a rule are such sick people that if you can alleviate any of their suffering, it’s a good thing,” Wood says.

This article originally appeared in the Respiratory Management May 2008 issue of HME Business.

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