JPD: What are the characteristics of long-term changes in cognitive and motor impairment in Parkinson's patients?

Efforts are increasing to identify potential risk factors for cognitive decline and the development of dementia in Parkinson's disease (PD)
.
About 30-40% of Parkinson's patients have cognitive impairment, and the prevalence increases over the course of the disease, reaching 50% after 10 years and 80% 20 years after diagnosis

Cognitive conditions associated with Parkinson's disease are heterogeneous
.
Deficits in executive function as well as attention and working memory frequently appear in the early stages of PD due to known anterior striatal dysfunction

Patients can be classified as tremor-dominant (TR-D), postural instability disorder (PIGD), or nondetermined (ND) motor phenotype
.
Patients have also been classified into tremor-dominant, bradykinetic, and mixed phenotypes

Likewise, motor phenotype may also influence the progression of cognitive impairment, as evidence suggests that patients with PIGD not only exhibit faster cognitive decline, but also have a greater risk of dementia and higher rates of depression
.
This may be particularly relevant to the role of the motor phenotype and the progression of cognitive impairment, since patients initially presenting with TR-D tend to convert to PIGD over the course of the disease

Here, Jennifer Michels of RWTH Aachen University Hospital in Germany used long-term data from the DEMPARK/LANDSCAPE study to assess the predictive value of cognitive impairment progression and exercise phenotypes for cognitive decline in PD
.

They included six-year longitudinal data on demographic, clinical, and neuropsychological data from 711 PD patients (age: M = 67.
57; 67.
4% were male)
.
And calculated the Z-transform composite score in the cognitive domain

To minimize missing data and dropouts, they used linear mixed models to evaluate three-year follow-up data from 442 PD patients for the specific role of exercise phenotype on cognitive decline (age: M = 66.
10; 68.
6% male)
.

They found that motor symptoms increased over the course of the disease, while MMSE and PANDA remained stable across all subgroups
.

After a three-year follow-up, PIGD patients showed a significant decrease in overall cognitive ability, and motor phenotypes differed in attention (β=-0.

In addition, PIGD patients more often experience difficulties in daily life
.

The significance of the study lies in the discovery that, over a three-year period, different PD motor phenotypes have distinct patterns of neuropsychological progression , with early executive deficits producing more amnestic features later in the process
.
In particular, patients with PIGD worsened over time compared with patients with TR-D and ND, highlighting a greater risk of dementia with this motor phenotype

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