MAPT and Parkinson disease: In the non-demented groups, including non-demented controls and PD patients, increased levels of T-tau were correlated to increased levels of YKL-40 (non-demented controls: Spearman’s rho = 0.5109, p = 0.0017; PD: Spearman’s rho = 0.4881, p = 0.004).