Degenerative diseases of the central nervous system are a large and varied group of disorders that affect a range of neurologic function. Sleep disorders are commonly seen in patients with cerebral degenerative diseases. Much of this may be related to the underlying central nervous system damage to sleep regulatory centers of the brain. Research has shown that sleep disorders may serve as a biomarker to predict development of a future neurodegenerative disorder. Increasing new data has suggested that disrupted sleep may accelerate the degenerative process in conditions such as Alzheimer dementia and Parkinson disease. One potential mechanism is emerging evidence of the role of sleep in glymphatic clearance of metabolic waste products from the brain. Studies have demonstrated increased levels of beta-amyloid in cerebrospinal fluid of subjects with insomnia and disrupted sleep. Prompt attention to and treatment of sleep symptoms can result in significant improvement in quality of life, or possibly delay in progression of disease, and improvement in caregiver burden.
| || |
• Sleep disorders, such as chronic insomnia disorder, sleep apnea, restless legs syndrome, certain parasomnias, and circadian rhythm disorders, are disproportionally more common in patients with cerebral degenerative disorders than in the general population.
| || |
• Sleep disturbances in the setting of neurodegenerative disorders are sometimes secondary to localized damage to areas of the brain that control and regulate sleep and alertness.
| || |
• REM-sleep behavior disorder is a parasomnia frequently seen in patients with Parkinson disease and other alpha-synucleinopathies and can sometimes predate the motor and cognitive symptoms of the condition by several years or even decades. It is the first time that a sleep disorder can be used as a biomarker to predict a neurodegenerative disorder.
| || |
• Treatment of the underlying sleep disorder can not only help in improving quality of life, but may improve motor or cognitive symptoms of the underlying cerebral degenerative condition.
| || |
• There is emerging evidence that diagnosis and treatment of sleep disorders may delay onset or progression of neurodegenerative conditions such as dementia.
Historical note and terminology
The relationship between sleep disorders and neurodegenerative diseases has become increasingly more lucid as research into both areas has made significant progress. Indeed, a link between the 2 has been noted since the earliest descriptions of some neurodegenerative disorders. In the early 19th century, James Parkinson and his coworkers described clinical sleep abnormalities associated with extrapyramidal disorders (103). Subsequently, a variety of sleep disorders have been found in tandem with diseases such as Parkinson disease, multiple system atrophy, dementia with Lewy bodies (DLB), corticobasal degeneration, and others. However, the underlying sleep abnormalities were not extensively explored until relatively recently. In the latter half of the twentieth century, the advent of more sophisticated diagnostic techniques, such as polysomnography and improved EEG recordings, as well as the discovery of new treatments, allowed for major advances in the field (103). Emerging research is exploring how disrupted sleep may serve as a risk factor for developing neurodegenerative disorders or accelerating progression of the disease.