MAPT and Parkinson disease: Reduced CSF levels of p-tau (SMD = −0.495, 95% CI: −0.689 to −0.301) and t-tau (SMD = −0.626, 95% CI: −0.888 to −0.365) and higher Aβ42 levels (SMD = 0.775, 95% CI: 0.498 to 1.052) were observed in PD patients relative to DLB patients.