Neurological Diseases May Be Preceded by Sleep Disorder
Parkinson’s disease, multiple system atrophy, and dementia may have preclinical symptoms, such as idiopathic REM sleep behavior disorder (RBD), lasting for decades in some cases according to new research published online July 28 in the journal Neurology.
Rapid eye movement (REM) sleep behavior disorder (RBD) is a sleep disorder characterized by loss of normal voluntary muscle atonia (sleep paralysis) during REM sleep. During REM sleep, which is the deepest part of the sleep cycle, the body is “disconnected” from the brain, leaving the body unable to move. Patients with RBD have REM sleep with excessive movements, some that may be potentially injurious or disruptive such as punching, shouting, getting out of bed, or flailing arm movements. It is estimated that 0.5% of the general population has RBD.
Daniel O. Claassen MD of the Mayo Clinic College of Medicine analyzed data from 27 patients with a history of RBD that preceded the onset of Parkinson’s disease, Parkinson’s dementia, multiple system atrophy, or dementia with Lewy bodies by at least 15 years. The vast majority of the participants (24) were male.
The patients' mean age at onset of the sleep disorder was 49 and at onset of neurologic symptoms was 72 (overall median onset of 25 years). At the latest follow up, 63% of the patients had progressed to dementia. The long preclinical phase has important implications for the development of therapies that may slow or halt the progression, say the authors of the study.
Parkinson’s disease belongs to a group of conditions called motor system disorders, with the primary symptoms being trembling in hands, arms, legs, or face; rigidity or stiffness of the limbs and trunk; bradykinesia (slowness of movement); and postural instability or impaired balance and coordination. It usually affects people over the age of 50. At present, there is no cure for Parkinson’s disease.
Dementia can also result from the brain changes that occur in Parkinson’s. The prevalence of dementia in Parkinson’s disease ranges from 20-40%. Patients may also have Alzheimer’s disease and cerebrovascular disease as co-morbid conditions.
Another common type of progressive dementia is Dementia with Lewy bodies (DLB). The central feature of DLB is progressive cognitive decline, combined with pronounced fluctuations in alertness and attention, recurrent visual hallucinations, and parkinsonian motor symptoms. Patients may also suffer from depression. Like both Alzheimer’s and Parkinson’s dementias, there is no cure.
Multiple System Atrophy (MSA) is a rare condition that causes symptoms similar to Parkinson’s, however, patients have more widespread damage to the autonomic nervous system that controls heart rate, blood pressure, and digestive system muscles. As with Parkinson’s, there is no cure for MSA. It is most often diagnosed in men older than 60.
Claassen D, et al "REM sleep behavior disorder preceding other aspects of synucleinopathies by up to half a century" Neurology 2010; 75: 494-499.
Mahowald M, et al "When and where do synucleinopathies begin?" Neurology 2010; 75: 488-489.