MAPT and Parkinson disease: Specifically, lower CSF levels of phosphorylated tau181, (pTau), total tau (tTau), amyloid beta 1−42 (Aβ1−42), and α-synuclein were found in early PD relative to controls (30); findings that were confirmed by the same research team in a subsequent study using a larger cohort (31), though Aβ1−42 in this study was not significantly lower in early PD relative to controls.