Sleep Apnea and CMT

Studies show CMT tends to come with Disturbed Sleep, Depression, and Reduced Quality of Life. Bummer! 😞

This post summarizes the scientific research I’ve absorbed on the subject of CMT and sleep apnea. It’s definitely accurate relative to my own experience in the past year or so.

It’s no surprise: nobody does well with regularly impaired or fragmented sleep β€” and it’s worse if it’s chronic or coupled with low oxygen and/or high carbon dioxide levels. Unfortunately many of these difficulties may apply to people with CMT as they age.

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 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 they 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, 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 QoL Charts)

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.

β€” Cordeiro, J. L., Marques, W., Hallak, J. E., & OsΓ³rio, 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 on the market for one with a mask that makes me look like Cthulhu or Immortan Joe. πŸ¦‘

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.” πŸ‘€

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 rare and extreme cases, CMT has been associated with phrenic nerve impairment and therefore diaphragm dysfunction. (The phrenic nerve connects your spinal cord to your diaphragm.) However, neuropathy-related diaphragm weakness is not a cause for sleep apnea; instead, the cause may be pharyngeal muscles and nerves affected by neuropathy β€” something that has been observed with CMT2C. However, this suggested cause has been questioned on the assumption that central sleep apnea, which commonly coincides with CMT, cannot have a cause in neuropathy as obstructive sleep apnea might. The researchers linking CMT and sleep apnea 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.)

My hunch is that sleep apnea has a lot of possible causes, and CMT can be a cause of those causes even if it’s not a direct cause. CMT definitely tends to put a damper on mobility and thus physical activity and exercise. That makes it even harder to keep your weight down as you age, and at the same time your CMT-related pain and mobility impairment is likely worsening as well. Driving up BMI alone highly increases your risk for sleep apnea.

A direct link between some types of CMT and sleep apnea may exist in other (or multiple) causes. For example, a 2007 review of the medical literature on CMT and pulmonary dysfunction notes:

Vocal cord dysfunction, possibly due to laryngeal nerve involvement, is found in association with several CMT types and can often mimic asthma. 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.

β€” Aboussouan LS, Lewis RA, Shy ME. Disorders of pulmonary function, sleep, and the upper airway in Charcot-Marie-Tooth disease. Lung. 2007 Jan-Feb;185(1):1-7. Epub 2007 Feb 9. Review. PubMed PMID: 17294338.

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 Non-Invasive Ventillation (NIV) machines as generally (or at least sometimes) preferable to CPAP machines.

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.

While it is quite rare with CMT, 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! πŸ™πŸ»

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