MAPT and Parkinson disease: This is based on predictors determined from our long-term population-based incident PD cohort study, CamPaIGN (Cambridgeshire Parkinson’s Incidence from GP to Neurologist), namely, impaired pentagon copying, semantic fluency performance and the MAPT H1/H1 genotype,1,10,11,28 with the latter chosen as a genetic predictor with particular relevance given our aim to investigate tau accumulation.