An estimated 17,730 new cases of spinal cord injury (SCI) occur each year in the United States, not including those that result in death at the time of injury.1 Poor sleep quality – a consistent but underrecognized patient-reported outcome – is common among this population and may result in fatigue, excessive daytime sleepiness, impaired concentration, and reduced quality of life. Roughly 40% of more than 300,000 people living with SCI were found to have an elevated risk of developing psychological comorbidity such as depression or anxiety disorder. Researchers postulate that impaired sleep may be a factor in the pathogenesis of these conditions.2

Sleep-disordered breathing (SDB) has been observed in 62% of SCI patients at 4 weeks postinjury, and chronic SDB has been reported in 40%-91% of the same population.3,2 “Multiple mechanisms predispose to the development of SDB in SCI… [including] increased upper airway collapsibility, a reduced dilator muscle responsiveness/effectiveness, a reduced arousal threshold, and an unstable ventilatory control system,” wrote authors of a recent review published in Nature of Science and Sleep.2 It as been posited that the various medications used in the management of patients with SCI – muscle relaxants, sedatives, and narcotics – could be one of factors that may influence these mechanisms.2

Along with poor sleep quality and daytime sleepiness, studies have linked multiple adverse outcomes to SDB in SCI, including deficits in attention and information processing that were shown to represent the equivalent of 31 years of additional aging.4 Research published in Neurology highlights the cerebrovascular risks associated with disordered sleep in SCI. Results confirmed the high risk of chronic fatigue (odds ratio [OR] 7.9; 95% CI, 3.5-16.2) and SDB (OR 3.1; 95% CI, 1.3-7.5) in patients with SCI. As well, investigators provided evidence that SDB is closely associated with impaired cerebrovascular responsiveness to CO2 in those with SCI and may contribute to their increased risk for stroke.5 

“It is well-known that sleep-related breathing problems dramatically affect quality of life, daytime sleepiness, and the risk of chronic fatigue, stroke, coronary artery disease, workplace accidents, motor vehicle accidents, and potentially depression, anxiety, and more,” commented study coauthor Aaron A. Phillips, CSEP-CEP, PhD, assistant professor in the departments of physiology and pharmacology, cardiac sciences, and clinical neurosciences in the Cumming School of Medicine at the University of Calgary in Alberta, Canada. He added that “it may be that sleep-related breathing problems are a central player in the overall health and well-being of people with SCI” and thus should be managed aggressively when possible.


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A high prevalence of periodic leg movement disorder (PLMD) has also been observed among SCI patients, with a range of findings showing rates of 50%-100% in patients with a lesion above T10.2 In a 2018 investigation that examined 262 sleep study recordings from individuals with tetraplegia, PLMD was identified in 58.4% of patients.6

Other research demonstrates disrupted circadian rhythmicity of melatonin, a substantial phase advancement of temperature, and delayed rapid eye movement sleep onset in patients with tetraplegia, and these issues may contribute to impaired sleep quality.2 Additionally, in a 2019 web-based survey of 304 participants with SCI, more than one-half of patients reported insomnia symptoms.7

Further research is needed to elucidate the prevalence of various sleep disorders in SCI and identify optimal treatment strategies. “Given the high prevalence of sleep disorders in SCI, any substantial sleep-related complaints should be further evaluated so that appropriate treatment can be initiated,” the review authors wrote.2 “A comprehensive management approach should include behavioral and pharmaceutical therapies, and be aligned with ongoing management and rehabilitation goals,” they concluded.

For further insight on sleep disorders in SCI and implications for treatment, we spoke with lead author of the review published in Nature of Science and Sleep, Abdulghani Sankari, MD, PhD, who is an associate professor of medicine in the Division of Pulmonary/Critical Care and Sleep Medicine at Wayne State University School of Medicine in Detroit, Michigan.

What are some of the most common sleep disorders seen in patients with SCI, and what are their implications for a patient’s quality of life?

Primary sleep disorders such as SDB, sleep-related movement disorders, circadian rhythm sleep-wake disorders, and insomnia disorder are common conditions after SCI but remain underrecognized and underdiagnosed – and therefore untreated for most patients. The majority of individuals with SCI have poor sleep and SDB. SDB has major consequences for cardiovascular health, neurocognitive function, daytime sleepiness, and quality of life.

People with chronic SCI and SDB have reduced cognitive function that can be observed early after injury – specifically, poorer attention, information processing, and recall compared to controls with mild SDB. Nearly all patients with SCI have poor sleep quality, excessive daytime sleepiness, and/or fatigue. One in 5 persons with SCI have hypertension or cardiac disease.8 Furthermore, cardiac medication use has been found to be higher in tetraplegic patients who have SDB, which may implicate a link between SDB and cardiovascular morbidities in patients with SCI.2

How should comorbid sleep disorders be addressed in this patient population, and what are some of the associated challenges?

Given the well-recognized increased prevalence of SDB in individuals with SCI and its impact on their quality of life and poor outcomes in the general population (heart disease, stroke, hypertension, and poor cognition), there is a critical need to increase awareness of this disorder and develop effective treatment interventions. Patients living with SCI face enormous difficulties in accessing high-quality care for sleep disorders, including inadequate recognition, limited access to sleep disorders centers, and difficulties using mechanical devices or positive airway pressure (PAP) therapy. 

Patients with SCI who need sleep studies such polysomnography should be referred to sleep centers that have the necessary expertise and resources to care for these patients, such as wheelchair access, availability of a lift, special wound care beds, and adequate training of staff.  

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What are additional considerations should clinicians take into account when managing patients with SCI?

Clinicians should assess individuals with SCI (T6 and above) for sleep disorders and refer them to specialized sleep disorder centers. Home sleep apnea testing (HSAT) is a convenient option but lacks empiric evidence of validity and reliability of event detection in SCI patients. Hypoventilation and high rates of central sleep apnea may limit the utility of HSAT for diagnostic purposes.

There is an increased risk of pulmonary complications, including delayed apnea, in patients with high cervical SCI and more complete injuries. Therefore, it may be prudent to consider early tracheostomy and ventilation in acute high cervical SCI (complete SCI above the level of C5), and noninvasive ventilation and assisted coughing techniques in lower cervical and thoracic level injuries.

PAP therapy is the treatment of choice for SCI patients with SDB; however, adherence to PAP therapy in this population remains a challenge despite education, follow-up, and support.

What should be the focus of further investigation in this area?

Large studies to determine the epidemiology and clinical manifestations of sleep disorders specific to individuals with SCI are needed. Given that the majority of individuals with SCI do not tolerate current traditional mechanical therapies such as PAP therapy, there is a critical need to identify mechanistic pathways using human and animal models. Such knowledge will inform the development and testing of novel pharmacological and nonpharmacological treatments that are both effective and tolerable. The effect of nonpharmacological treatments such as respiratory muscle training, dental appliances, and nerve stimulation in treating SDB in SCI also remains unstudied.

References

  1. National Spinal Cord Injury Statistical Center. Spinal Cord Injury Facts and Figures at a Glance. Birmingham, AL: University of Alabama at Birmingham, 2019.
  2. Sankari A, Badr MS, Martin JL, et al. Impact of spinal cord injury on sleep: current perspectives. Nat Sci Sleep. 2019;11:219-229.
  3. Berlowitz DJ, Brown DJ, Campbell DA, et al. A longitudinal evaluation of sleep and breathing in the first year after cervical spinal cord injury. Arch Phys Med Rehabil. 2005;86(6):1193-1199.
  4. Schembri R, Spong J, Graco M, et al; COSAQ study team. Neuropsychological function in patients with acute tetraplegia and sleep disordered breathing. Sleep. 2017;40(2).
  5. Squair JW, Lee AHX, Sarafis ZK, et al. Sleep-disordered breathing is associated with brain vascular reactivity in spinal cord injury. Neurology. 2019;93(24):e2181-e2191.
  6. Peters AEJ, van Silfhout L, Graco M, et al. Periodic limb movements in tetraplegia. J Spinal Cord Med. 2018;41(3):318-325.
  7. Shafazand S, Anderson KD, Nash MS. Sleep complaints and sleep quality in spinal cord injury: a web-based survey. J Clin Sleep Med. 2019;15(5):719-724.
  8. Sankari A, Martin J, Badr M. A retrospective review of sleep-disordered breathing, hypertenstion and cardiovascular diseases in spinal cord injury patientsSpinal Cord. 2015;53(6):496-497.