CMT Blog

This post summarizes the scientific research I’ve absorbed on the subject of CMT and sleep apnea while also reflecting on my own experience with both.

A 2014 study published in the Journal of Neurology, Neurosurgery & Psychiatry on sleep disorders and CMT concluded “CMT may predispose” people to obstructive sleep apnea and restless leg syndrome. Then, a 2015 study of an extended family with CMT2 found “that patients with CMT, in spite of not showing clinical signs of advanced respiratory impairment, may present subclinical respiratory changes. The respiratory comprise in the CMT disease can be silent and insidious without presenting characteristic clinical signals.”

While nobody does well with regularly impaired or fragmented sleep, it can be worse with CMT and more difficult to assess and treat for all its underlying causes which may emerge slowly and mysteriously over time.

Studies show CMT tends to come with disturbed sleep, depression, and reduced quality of life. 😞

A 2010 survey of 227 people with different types of CMT found they reported a lower overall health-related quality of life (HRQoL) than people without CMT. CMT was also correlated in this study’s result with Restless Legs Syndrome (RLS), especially in women. The survey focused on polling people with CMT about their experience of any fatigue, daytime sleepiness, reduced sleep quality, and restless legs using the Epworth Sleepiness Scale (which is often used to diagnose sleep apnea), the Pittsburgh Sleep Quality Index, the Multidimensional Fatigue Inventory, and the International RLS Severity Scale.

These diagnostic tools can be found online (see the links above) and self-administered if you are trying to get a sense of your sleep quality and whether you may have sleep apnea, RLS, and/or other conditions that make it hard to get good rest. Keep in mind these diagnostic surveys are just educated guesswork. I scored in the moderate risk range on most of the apnea-related self-diagnostic surveys, but actual, week-long analysis with a home sleep apnea test machine showed I am often getting a lot more interrupted sleep and low blood oxygen than I ever anticipated.

Body Mass Index (BMI) is a significant factor in most of the sleep apnea diagnostics, which makes sense. With some luck and good habits around exercise/sleep/eating (and their timing), I find I can reduce my apnea symptoms, but even at my best they can be pretty bad. Once in a while I get great sleep and feel refreshed after a late night of drinking too, so go figure! 🍻

Sleep your way to the top (of the Quality of Life charts).

A recent study shows CMT is more likely to come with bad sleep and depression:

Patients with CMT exhibited an increased trend toward depressive symptoms compared with the general population. In addition, CMT patients were exposed to a higher risk of reduced quality of life and significant sleep impairment.

— Cordeiro, J. L., Marques, W., Hallak, J. E., & Osório, F. L. (2014). Charcot-Marie-Tooth disease, psychiatric indicators and quality of life: a systematic review. ASN neuro, 6(3), 185–192. doi:10.1042/AN20130048

It also works in reverse: if you have disordered sleep and breathing, alleviating those problems can help improve your neuropathy symptoms, as this 2018 case study shows. In this case study that involves a woman in her 50s, a continuous positive airway pressure (CPAP) machine improved her life a lot. Having tested one myself recently with the full face mask, I am impressed they’re almost comfortable. I’m looking for one with a mask that makes me look like Cthulhu or Immortan Joe. 🦑

Sleep Apnea often coincides with CMT1, less with CMT2.

A 2001 study published in The Lancet found than in an extended family with CMT1A, there was a very strong correlation between the CMT and sleep apnea. Subsequent studies have added more support for the conclusion that CMT and sleep apnea are somehow related. (At least this may be true for the demyelinating types of CMT, i.e., CMT1.) Additionally this study found “[t]he severity of neuropathy and sleep apnoea were higher in male CMT individuals and were correlated with age and body mass index.” 👀

Disturbed sleep is common with CMT2, but Apnea is less often the cause.

People with CMT2, in contrast with CMT1, have shown a lower incidence of sleep apnea while still experiencing disturbed sleep. For this group, daytime sleepiness is commonly reported, and “a reduction in REM sleep, in addition to a high arousal index” has been observed. Also, more severe cases of CMT2 are more likely to be coupled with sleep apnea. (My guess is this is where I’ve landed myself.)

Why and how CMT may cause respiratory and cardio-pulmonary problems

In some Japanese case studies (1992, 2000), and a (2014) Belgian study, CMT was associated with phrenic nerve impairment and diaphragm dysfunction. (The phrenic nerve travels from the spinal cord to the diaphragm.) In the past, these were considered “rare” cases. However, a 2005 study argued diaphragm weakness “may be more common than generally acknowledged” with CMT.

👉 There’s a Facebook Group for people dealing with phrenic nerve impairment, and the CMTA has some useful information about it in relation to breathing problems and CMT.

Diaphragm dysfunction and phrenic nerve involvement may complicate the effects of apnea but do not cause it.

Notably, neuropathy-related diaphragm weakness is not a cause for sleep apnea. It might complicate apnea by keeping too much carbon dioxide and too little oxygen in one’s bloodstream, but the apnea likely has a cause higher up the respiratory system: pharyngeal muscles and nerves affected by neuropathy. This has been observed with CMT2C, but there was a countering opinion to the extended family study in 2001 that questioned how central sleep apnea, which commonly coincides with CMT, could have a cause in neuropathy as obstructive sleep apnea might. In response to this objection, which assumes most CMT and sleep apnea cases involve central sleep apnea, the original researchers linking CMT, the pharyngeal nerve, and sleep apnea said they believe there is significant overlap between central and obstructive sleep apneas, so “pharyngeal neuropathy, combined with hypocapnia, accounts for [both] obstructive and central sleep apnoeas.” (My emphasis.)

A 2007 meta-review (synthesis of research to date) of “Disorders of Pulmonary Function, Sleep, and the Upper Airway in Charcot-Marie-Tooth Disease” constellates “restrictive pulmonary impairment, sleep apnea, restless legs, and vocal cord dysfunction.”

Key findings:

• The pulmonary impairment may be caused by “phrenic nerve dysfunction, diaphragm dysfunction, or thoracic cage abnormalities.”
• The central sleep apnea “may be associated with diaphragm dysfunction and hypercapnia, whereas obstructive sleep apnea has been reported as possibly due to a pharyngeal neuropathy.”
• “Restless legs and periodic limb movement during sleep are found in a large proportion of patients with CMT2, a type of CMT associated with prominent axonal atrophy.”
• “Vocal cord dysfunction, possibly due to laryngeal nerve involvement, is found in association with several CMT types and can often mimic asthma.”

My takeaways:

After reading through this literature and thinking about my own experience, it seems pretty clear that sleep apnea has a lot of possible causes, and CMT can cause some of those causes, making CMT only indirectly related but still related. CMT definitely tends to put a damper on mobility and therefore your physical activity and exercise. Lack of exercise makes it even harder to keep your weight down as you age. Lack of exercise, weight gain, and aging with a progressive disability do nothing to prevent anxiety and depression, which many people respond to by over-eating and sedentary living. Even if you weather this all pretty well, your CMT-related pain and mobility impairment is still a grind that only gets worse. Driving up BMI alone highly increases your risk for sleep apnea, so if there is one thing you can do to help yourself, it’s to keep your weight down — a key to health and longevity for everyone.

BiPAP, CPAP, or NIV?

If you are diagnosed with sleep apnea, you’re likely to be told you need a nighttime assistive breathing device like a CPAP machine. However, CMT and any other breathing-related abnormalities you have may complicate the question of what device is best for you and which might actually be harmful. The 2007 meta-review I summarized above states:

There may be special therapeutic considerations for the treatment of those conditions in individuals with CMT. For instance, bi-level positive airway pressure [BiPAP] may be more appropriate than continuous positive airway pressure (CPAP) for the treatment of sleep apnea in the individual with concomitant restrictive pulmonary impairment.

— “Disorders of Pulmonary Function, Sleep, and the Upper Airway in Charcot-Marie-Tooth Disease“

This possibility of BiPAP machines being better than CPAP for some CMT cases is echoed and asserted even more strongly in this article on the CMTA website by Dr. Ashraf Elsayegh, which also recommends other types of Non-Invasive Ventillation (NIV) machines as generally (or at least sometimes) preferable to CPAP machines, although some CPAP devices now include some responsive, variable pressure features.

Dr. Elsayegh’s article and this talk he gave in 2018 explains the conditions under which he recommends different devices:

If you have been diagnosed with sleep apnea and have CMT, Dr. Elsayegh says an overnight sleep study should be done. This will help identify whether you have central or obstructive sleep apnea and whether any muscle weakness is impacting your night time breathing. Lung/breathing tests can also be done at a lab or hospital. Normally these tests are done while sitting or standing, but diaphragm weakness may show itself in results if the tests are done in different postures, including lying down.

While it is quite rare with CMT in otherwise healthy people, if you are not able to take in enough oxygen and/or exhale enough carbon dioxide while you are sleeping, getting the right supportive device is critical. Both hypoxemia and hypercarbia can be caused by sleep apnea. (Hypoxemia is when you have very low blood oxygen levels. Hypercapnia or hypercarbia refers to elevated carbon dioxide levels in the bloodstream.)

I am still working through CMT and sleep apnea diagnoses myself, so please let me know if I missed something or got it wrong. All tips, resources, and related questions are very appreciated too! 🙏🏻 How have you dealt with CMT and sleep apnea?