Plasma total tau predicts executive dysfunction in Parkinson's disease

Cognitive impairment is an important non-motor aspect of Parkinson's disease (PD). Amyloid-β and tau pathologies are well-established in Alzheimer's disease and commonly coexist with synucleinopathy in PD. However, the levels of these biomarkers in the plasma of patients with PD and their relationship with specific cognition domains remain to be clarified. The current study compared the motor severity and neuropsychological assessment of general and specific cognition, with plasma levels of α-synuclein (α-syn), amyloid-β 42 (Aβ42), and total tau (t-tau) in PD subjects.

Plasma levels of α-syn, Aβ42, and t-tau were measured in 55 participants with PD through immunomagnetic reduction assay. The evaluation of motor severity and comprehensive neuropsychological assessment was performed in all participants.

The level of plasma α-syn was negatively correlated with the scores of Unified Parkinson's Disease Rating Scale part III [r = (-.352), p = .008]. The level of plasma t-tau was negatively correlated with the scores of digits recall forwards and digits recall backwards [r = (-.446), p = .001; r = (-.417), p = .002, respectively]. No correlations were found between the levels of α-syn and Aβ42 and any neuropsychological tests.

This study concluded a lower level of plasma α-syn was correlated with motor dysfunction in PD patients, and a higher level of plasma t-tau was correlated with lower cognitive performance, especially for attention and executive function. These results propose the possibility of using plasma biomarkers to predict specific cognitive performance in PD subjects.