Researchers have found new biomarkers that may improve the ability of clinicians to predict which patients in the early stages of Parkinson’s disease will suffer cognitive impairment within the first three years of their diagnosis, a new study says.
These biomarkers include deficits in dopaminergic circuits (neurons that produce dopamine, which is lacking in Parkinson’s disease), brain atrophy, presence of Alzheimer’s disease markers, and genetic factors.
The study is titled “Multiple modality biomarker prediction of cognitive impairment in prospectively followed de novo Parkinson disease” and was published in the journal PLoS One.
“The results of this study improve our understanding of the changes in brain function that occur with initial cognitive changes in early Parkinson’s disease,” Daniel Weintraub, MD, the study’s principal researcher, said in a news release. “This could eventually lead to improved clinical care and development of therapies to treat this symptom.”
Researchers analyzed medical data and samples from 423 newly diagnosed and untreated Parkinson’s disease patients. These patients had no history of dementia when they enrolled in the Parkinson’s Progression Markers Initiative (PPMI), an international study started in 2010 and sponsored by The Michael J. Fox Foundation for Parkinson’s Research.
Researchers used brain scans, such as MRIs, to assess brain changes; samples of cerebrospinal fluid (CSF) to analyze the levels of Parkinson- and Alzheimer-related proteins; and genetic tests to identify gene variations underlying cognitive impairment.
By year three of the study, 15–38 percent of the patients experienced cognitive deficiencies. Researchers found that cognitive impairment was associated with dopamine deficiency, loss of brain volume or thickness, low levels of beta-amyloid protein (a marker for Alzheimer’s disease) in the CSF, and mutations in the genes COMT and BDNF.
According to researchers, these findings provide “confirmation for heterogeneity in the neural substrate of the early cognitive deficits in [Parkinson’s disease].” They also wrote that their findings highlight “the need to incorporate multiple biomarkers” in assessing risk factors for cognitive decline.
The study has some limitations, such as the fact that PPMI participants were mostly male, white and highly educated, which limits the generalization of the results to other patients.
“Validation and extension of these findings will help in the design of clinical trials for cognitive impairment in [Parkinson’s disease], including those testing possible disease-modifying therapies from disease onset, and also be a step toward personalized medicine,” researchers wrote.