Those with spinal muscular atrophy (SMA) often suffer from sleep disorders, but the specific reasons for sleep disturbances vary. For instance, some studies on SMA report sleep disturbances resulting from breathing disorders like sleep apneas, whereas others report problems with the architecture of sleep, which can be identified through polysomnography.1–9 Though research that groups patients with the different types of SMA has found that, compared to those without SMA, those with SMA are more likely to spend more time in stage 1 of sleep and less or no time in rapid eye-movement, the nature and quality of sleep may differ depending on the type of SMA a particular patient has.9
Those with SMA type 1 or SMA type 2 may be more prone than those with other forms of the disease to abnormalities in the microstructure of sleep and experience more difficulty waking.6–9 Reduced arousability has been reported during non-rapid eye movement in patients with SMA type 1 who display abnormal sleep architecture.6 However, noninvasive ventilation employed at night has been shown to improve abnormalities in sleep architecture in both SMA type 1 and SMA type 2 patients.8
The Sleep Disturbance Scale for Children (SDSC) questionnaire is a research tool that has been used to evaluate disordered sleep across several diseases.10 According to this tool, more than 16% of those with SMA display abnormal sleep patterns, compared to just 5% of the general population.11 Nonetheless, this tool may not capture the full extent of sleep disturbances that may be experienced in SMA, and it may also fail to identify patients whose sleep disturbances are limited to a specific type of disturbance but who do not display a broad range of sleep problems.10
An analysis of SDSC data from SMA patients revealed that in addition to the roughly 16% identified through the SDSC as having disordered sleep, an additional 16.7% demonstrate abnormalities in at least one category of sleep.10 Breathing disorders experienced during sleep, as well as difficulty falling asleep and staying asleep were the most commonly found sleep issues in those with SMA. Excessive sleepiness and night sweats were other frequently experienced factors disturbing sleep. Some data suggest that night sweats in SMA occur most frequently amongst younger patients with SMA type 2.
While some of the sleep disturbances associated with SMA may be directly impacted by SMA pathogenesis, some researchers have also suggested that difficulty in moving out of uncomfortable positions could account for some of the sleep disturbances that SMA patients suffer and could also offer potential for interventions to improve sleep.10 Data have shown that those who can roll halfway over score better in sleep disturbance tests than those unable to roll halfway over. Those wearing night splints for orthopedic purposes have also been shown to score normally on the SDSC, suggesting that orthotic devices do not themselves disturb sleep.
As research on sleep disturbances occurring in SMA evolves, there will likely be growing opportunities to improve the quality of sleep in SMA patients. To improve sleep in all SMA patients, it will be important to continue to elucidate the different types of sleep disturbances that these patients experience and the underlying causes for these disturbances. As a one-size-fits-all approach is unlikely to improve sleep for all of those who with SMA who suffer sleep disturbances, clarifying the distinct ways in which sleep becomes disordered in this patient population will help ensure that each patient receives sleep interventions that are optimized for their specific circumstances.
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