Frequently present features include apathy, depressed mood, anxious mood, hallucina- tions, delusions, personality changes, rapid eye movement sleep behavior disorder, and excessive daytime sleepiness.
The prevalence of Parkinson’s disease in the United States steadily increases with age from approximately 0.5% between ages 65 and 69 to 3% at age 85 years and older. Parkinson’s disease is more common in males than in females. Among individuals with Parkinson’s disease, as many as 75% will develop a major NCD sometime in the course of their disease.
The prevalence of mild NCD in Parkinson’s disease has been estimated at 27%.
Onset of Parkinson’s disease is typically between the sixth and ninth decades of life, with most expression in the early 605. Mild NCD often develops relatively early in the course of
Parkinson’s disease, whereas major impairment typically does not occur until late.
Environmental. Risk factors for Parkinson’s disease include exposure to herbicides and pesticides.
Genetic and physiological. Potential risk factors for NCD among individuals with Par— kinson’s disease include older age at disease onset and increasing duration of disease.
Neuropsychological testing, with a focus on tests that do not rely on motor function, is crit- ical in detecting the core cognitive deficits, particularly at the mild NCD phase. Structural neuroimaging and dopamine transporter scans, such as DaT scans, may differentiate
Lewy body—related dementias (Parkinson’s and dementia with Lewy bodies) from non—
Lewy body—related dementias (e.g., Alzheimer’s disease) and can sometimes be helpful in the evaluation of major or mild NCD due to Parkinson’s disease.
Major or mild neurocognitive disorder with Lewy bodies. This distinction is based sub- stantially on the timing and sequence of motor and cognitive symptoms. For NCD to be at- tributed to Parkinson’s disease, the motor and other symptoms of Parkinson’s disease must be present well before (by convention, at least 1 year prior) cognitive decline has reached the level of major NCD, whereas in major or mild NCD with Lewy bodies, cognitive symp- toms begin shortly before, or concurrent with, motor symptoms. For mild NCD, the timing is harder to establish because the diagnosis itself is less clear and the two disorders exist on a continuum. Unless Parkinson’s disease has been established for some time prior to the onset of cognitive decline, or typical features of major or mild NCD with Lewy bodies are present, it is preferable to diagnose unspecified mild NCD.
Major or mild neurocognitive disorder due to Alzheimer’s disease. The motor features are the key to distinguishing major or mild NCD due to Parkinson’s disease from major or mild NCD due to Alzheimer’s disease. However, the two disorders can co-occur.
Major or mild vascular neurocognitive disorder. Major or mild vascular NCD may pre- sent with parkinsonian features such as psychomotor slowing that may occur as a conse- quence of subcortical small vessel disease. However, the parkinsonian features typically are not sufficient for a diagnosis of Parkinson’s disease, and the course of the NCD usually has a clear association with cerebrovascular changes.
Neurocognitive disorder due to another medical condition (e.g., neurodegenerative disorders). When a diagnosis of major or mild NCD due to Parkinson’s disease is being considered, the distinction must also be made from other brain disorders, such as progres- sive supranuclear palsy, corticobasal degeneration, multiple system atrophy, tumors, and hydrocephalus.
Neuroleptic-induced parkinsonism. Neuroleptic-induced parkinsonism can occur in individuals with other NCDs, particularly when dopamine-blocking drugs are prescribed for the behavioral manifestations of such disorders