Sleep-disordered breathing in neurodegenerative diseases

Sleep disorders are common in neurodegenerative diseases such as Parkinson's disease (PD), multiple system atrophy (MSA), amyotrophic lateral sclerosis (ALS), hereditary ataxias, and Alzheimer's disease (AD). Type, frequency, and severity of sleep disturbances vary depending on each of these diseases. Cell loss of the brainstem nuclei that modulates respiration, and dysfunction of bulbar and diaphragmatic muscles increase the risk for sleep-disordered breathing (SDB) in MSA and ALS. The most relevant SDB in MSA is stridor, whereas in ALS nocturnal hypoventilation due to diaphragmatic weakness is the most common sleep breathing abnormality. Stridor and nocturnal hypoventilation are associated with reduced survival in MSA and ALS. In contrast, sleep apnea seems not to be more prevalent in PD than in the general population. In some PD patients, however, coincidental obstructive sleep apnea (OSA) can be the cause of excessive daytime sleepiness (EDS). SDB can also occur in some hereditary ataxias, such as stridor in spinocerebellar ataxia type 3 (Machado-Joseph disease). The presence of concomitant OSA in patients with AD can have deleterious effects on nocturnal sleep, may result in EDS, and might aggravate the cognitive deficits inherent to the disease. However, whether OSA is more frequent in patients with AD than in the general population is uncertain. Recognition of SDB in neurodegenerative disease is important because they are associated with significant morbidity and potential effective treatments are available.