Obstructive sleep apnea (OSA) is a mechanical breathing problem which occurs when the tissues of the upper airway collapse during sleep.
This leads to pauses in breathing that can, at the very least, disrupt one’s sleep. At the very worst, OSA can lead to other problems. These include oxidative stress on the heart, glucose intolerance, and drug-resistant hypertension.
Someone with multiple sclerosis (MS) who also has untreated OSA can expect fatigue to become insurmountable. They will likely experience higher sensitivity to pain, greater cognitive difficulty, and a higher chance for having accidents or falling.
OSA is more prevalent than most people know. It can happen to anyone, no matter their gender, size, age, or physical status.
However, there’s another kind of sleep apnea that isn’t as common. Yet, it can be just as dangerous to leave untreated, and is especially problematic for people with MS.
What is Central Sleep Apnea?
Central sleep apnea (CSA) is similar to OSA in that it leads to long pauses in breathing as one sleeps. The dangerous consequences of these pauses in breathing, and the lack of oxygen they culminate in, are the same.
However, CSA refers to a condition of the central nervous system in which the brain doesn’t send proper signals to the muscles that control breathing as you sleep (most critically, the diaphragm).
These signals are part of the structure of the autonomic nervous system, the one that keeps your organs working even as you sleep. Autonomic means “independent of the conscious mind.” That is to say, your brain should still be in charge of breathing even if you’re not aware of it.
Apnea means “no breath”
This is the case during the day. If you “feel” out of breath, you don’t instinctively “hold” your breath, you “take” a breath. This is because your body, when out of biochemical balance, will respond, often consciously, to correct itself.
People can experience apnea throughout the day without even knowing it. Maybe they are holding their breath while watching a scary movie, or exercising. Daytime apnea inspires “feelings,” such as dizziness, to remind us to breathe.
This is part of the reason why we sigh or yawn, as well. It’s the body’s way of correcting oxygen imbalances.
But when you’re asleep, it’s a different matter. Unconscious, you’re in no position to make decisions about anything. You rely on your brain to know you are asleep and trust it will regulate your breathing in the meantime.
Who’s minding the controls at night?
When CSA strikes, it’s as if the little elf running the control panel in the brain has gone out for a coffee break. (In all seriousness, this is how I have explained it to patients in the sleep lab.)
While they are out, the brain may fail to signal the diaphragm to do its job. This leaves you simply in repose, not breathing, not unlike a corpse.
Eventually, alarms kick in, because our bodies are designed with backup systems galore (thank goodness!). The balance of oxygen to carbon dioxide in the bloodstream inspires these critical alarms.
While inhaling is important for oxygen intake—our red blood cells distribute healthy oxygen to every organ in the body—those same cells also collect carbon dioxide, a waste product, for delivery to the respiratory system, which expels it with every outgoing breath.
With CSA, not only is there no incoming breath, there is no outgoing breath.
This creates a condition of too much carbon dioxide in the bloodstream as well as not enough oxygen. Both situations generate chemical alarms in the nervous system which eventually provoke a return to breathing.
In other words, the elf returns from his coffee break and sends emergency orders to the diaphragm to go to work.
The problem is that, when that alarm has sounded, stress hormones enter the bloodstream and wake us up. This causes fragmented sleep and repeated awakenings, often accompanied by shortness of breath.
The curse of sleep fragmentation
A person with CSA may wake up all night, never knowing why they have done so. They may also suffer from bouts of insomnia.
Not surprisingly, this leads to feeling extremely sleepy during the day. Even if they never fully awaken at night, their sleep stages were probably spent in shallow sleep, so they never get a full night’s rest.
Shallow sleep does not supply the body and brain with the healing opportunities that deep sleep does.
And one cannot hope to achieve the restorative rapid eye movement (REM) sleep without first entering deeper stages of sleep.
REM typically doesn’t happen until after the other stages of sleep have occurred. It’s also an active period of sleep. It allows the brain to clean up its circuitry and compartmentalize memory and learning (among other things).
If we are prevented from sleeping more deeply on a regular basis, the result is nonrestorative sleep. This is not optional for good health and well being, but critical to it.
CSA and Multiple Sclerosis
For someone with MS, CSA is a major problem if left untreated. The brain of a person with MS needs as much of the healing and restoration of deep and REM sleep as they can get. CSA, if left undiagnosed and untreated, provides an ongoing roadblock to healthy sleep.
It also accelerates other unhealthy developments, such as Type 2 diabetes, cardiovascular diseases, mood disorders, dementia-like problems, strokes, and other chronic autoimmune conditions such as rheumatoid arthritis and irritable bowel syndrome.
Although MS doesn’t necessarily lead to the development of CSA, it can’t be ruled out as a potential outcome, either.
Links between CSA and MS
A 2012 study published in Neurology suggests that “the robust differences between subjects with MS and controls indicate that MS and, in particular, MS-related brainstem pathology, could increase vulnerability to OSA and central sleep apnea.”
Think about it: If the parts of your brain that work together to regulate breathing are damaged (either directly or indirectly), this can explain hiccups in message processing between the brain and the diaphragm.
We already know that the presence of MS can lead to scrambled communications circuits between the brain and other parts of the body, such as the bladder or muscles.
MS can also confuse our circadian rhythms, making it hard for the brain to regulate breathing during sleep; it may not be completely “aware” that we are, in fact, asleep.
Researchers in the study also pointed to “strong evidence that regional brainstem dysfunction due to MS plaque formation might contribute to both obstructive and central sleep apnea severity.”
This means that if you have sleep apnea, having MS is likely to worsen your condition.
The researchers for this study also point out that “although in the general population the prevalence of CSA is lower than that of OSA, patients with disorders such as MS that affect the brainstem may be at increased risk for CSA or apnea-related sudden death.”
In other words, these miscommunications between the brain and the respiratory system can be far more dangerous if we leave them undiagnosed and untreated.
What’s a person with MS to do?
If you have extreme fatigue and daytime sleepiness, or other symptoms that suggest sleep apnea (a loved one has witnessed you gasping in your sleep, for instance), it is never a bad idea to pursue a sleep study to rule out either form of apnea. You could have OSA, CSA, or a combination of the two, referred to as complex sleep apnea syndrome.
If your sleep specialist uncovers a case of CSA, they may refer you to a cardiologist for an evaluation. Your MS neurologist may also want to perform other tests. CSA can lead to systemic damage to the cardiovascular and nervous systems. Both specialists may want to look for signs of damage caused by previously untreated CSA.
Treatment for OSA typically includes positive airway pressure (PAP) therapy (usually continuous, or CPAP), whereas someone with CSA can get good results from using customized bi-level applications of PAP (BiPAP or BPAP). In more severe cases, a smart technology known as adaptive servo ventilation (ASV) can be effective.
THE GOOD NEWS
Treating either/both forms of sleep apnea can greatly improve many of the symptoms you endure as a person with MS, such as cognitive dysfunction, mood swings, or pain due to inflammation.