MAPT and dementia: Levels of CSF biomarkers more commonly associated with AD, that is, tau, P‐tau, and Aβ42, have been found to be normal or slightly decreased in PD when compared with controls.2, 3, 5 In AD, tau and P‐tau have been shown to be increased when compared with controls, whereas Aβ42 has been shown to be decreased when compared with controls.7, 8 In patients with PD with dementia, most studies have shown normal levels of tau and P‐tau when compared with controls and normal or decreased levels of Aβ42.