Defining the Characteristics of Mild Cognitive Impairment in Prodromal PD

Mild cognitive impairment has been proposed as a marker for the prodromal phase of Parkinson disease (PD), but little is known about its presentation in community-dwelling older adults.

A recent study out of China aimed to evaluate the frequency and clinical features of mild cognitive impairment (MCI) of older adults presumed to be in the prodromal phase of Parkinson disease (PD).

PD researchers are keenly interested in prodromal disease, with the idea that early interventions could have disease-modifying effects. Possible markers of early disease have been suggested, including rapid eye movement (REM) sleep behavior disorder, diminished smell, constipation, and autonomic dysfunction. But it is not known how predictive, sensitive, or specific these early signals are.

The time from the prodromal stage to an official clinical PD diagnosis could vary from 5 to 20 years, and the authors noted that longitudinal studies in this area are limited.

Since the International Parkinson and Movement Disorder Society has proposed MCI as a prodromal marker for PD, the researchers sought to examine community-dwelling older adults in East China.

This cross-sectional, prospective, community-based study, published in CNS Neuroscience and Therapeutics, recruited 2688 volunteers 50 years and older in 9 districts across Nanjing City between March 2017 and August 2020. After 25 volunteers were excluded, 2663 participants were included.

Of the 2663, 64 were determined to have possible or probable prodromal PD, and they were invited to participate further, but 8 of those patients left the study.

Twenty-two volunteers from the larger group were designated as healthy controls.

Fifty-six of the remaining participants with possible or probable prodromal PD continued with a hospital-based assessment; 7 were diagnosed as having possible prodromal PD, and 49 were diagnosed as having probable prodromal PD.

Of the 49 considered to be in the probable stage, 10 could not continue with a neuropsychological assessment, which included tests for memory, visuospatial function, language, attention/working memory, and executive function.

Of the 39 in the probable prodromal stage, 23 were found to have MCI and 16 had normal cognition.

The domains most frequently impaired were memory, followed by attention/working memory and executive function. Amnestic MCI multidomain phenotype was the most frequent MCI subtype in prodromal PD.

Additionally, worse cognitive status was linked with a decline in motor symptoms as shown by the Unified Parkinson’s Disease Rating Scale (part III) score, which measures motor function (r = −0.456; P = .004).

Recognizing this early in the prodromal stage could help clinicians strategize PD therapy earlier, the authors said.

The study had some limitations, such as the fact that it lacked neuroimaging data and that it was a single-center study.

Pan C, Li Y, Ren J, et al. Characterizing mild cognitive impairment in prodromal Parkinson’s disease: A community-based study in China. CNS Neurosci Ther. Published online November 25, 2021. doi: 10.1111/cns.13766