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A popular Alzheimer's biomarker may not translate well to Parkinson's. A new study found that plasma p-tau217 — a marker of early Alzheimer's disease — is not significantly linked to cognitive impairment in Parkinson's patients without dementia. Researchers say both Alzheimer's-related and Parkinson's-specific processes need to be considered when assessing cognitive decline in this population.
A biomarker widely used to detect early Alzheimer's disease may not be the right tool for spotting cognitive decline in Parkinson's disease (PD). A new study published in Movement Disorders found that plasma phosphorylated tau-217 (p-tau217) was not significantly associated with cognitive impairment in PD patients without dementia — even though these patients performed worse than healthy controls across multiple cognitive domains.
The study analyzed data from 165 PD patients and 58 healthy controls from the Quebec Parkinson Network. Despite lower cognitive scores in the PD group, plasma levels of p-tau217, GFAP, and neurofilament light chain (NfL) did not differ significantly between groups after statistical correction. Notably, APOE ε4 carriers had higher p-tau217 levels, but this didn't translate into worse cognitive outcomes.
Key Takeaways:
Why it matters: These findings signal that cognitive decline in Parkinson's is likely driven by PD-specific mechanisms beyond Alzheimer's pathology — meaning clinicians and researchers may need a broader, disease-specific biomarker toolkit to accurately assess and monitor cognition in this population.