Changes of cerebrospinal fluid Aβ42, t-tau, and p-tau in Parkinson's disease patients with cognitive impairment relative to those with normal cognition: a meta-analysis.

The cerebrospinal fluid (CSF) signature of reduced amyloid beta 1-42 (Aβ42), elevated total tau (t-tau), and phosphorylated tau181 (p-tau) is important for the early diagnosis of Alzheimer's disease (AD). Aβ42, t-tau, and p-tau have been reported in numerous studies to contribute to predicting cognitive impairment in Parkinson's disease (PDCI). However, no consistent conclusion can be drawn so far. Literatures regarding Aβ42, t-tau, and p-tau in CSF were systematically reviewed, and a meta-analysis was thus performed to evaluate the changes of these biomarkers in PDCI patients, including PD with mild cognitive impairment (PDMCI) and PD dementia (PDD) patients, relative to PD with normal cognition (PDNC) patients. Databases of "PubMed," "EBSCO," and "Springer" were retrieved for articles concerning Aβ42, t-tau, and p-tau in PDCI patients relative to those in PDNC patients published from January 1, 2000 to February 1, 2017. The following keywords were set, namely, "dementia" or "cognitive impairment" or "mild cognitive impairment" and "cerebrospinal fluid" and "Parkinson*." Sixteen articles comprising 590 PDCI patients and 1182 PDNC patients were included. The results showed that CSF Aβ42 level in PDCI cohort was lower than that in PDNC cohort (pooled Std.MD = -0.44, 95% CI [-0.61, -0.26], p < 0.00001). Reduced Aβ42 (pooled Std.MD = -0.60, 95% CI [-0.75, -0.45], p < 0.00001) as well as elevated t-tau (pooled Std.MD = 0.21, 95% CI [0.06, 0.35], p = 0.006) and p-tau (pooled Std.MD = 0.36, 95% CI [0.02, 0.69], p = 0.04) could be observed in PDD cohort compared with PDNC cohort. Therefore, amyloid pathology and tauopathy may participate in the development of PDD, which is similar to AD.