MAPT and Mental deterioration: Association between the MAPT H1/H1 genotype and cognitive dysfunction in PD was first reported in 2007 in a longitudinal study of a population-representative incident PD cohort (n = 108): over a mean (SD) follow-up of 3.5 (0.7) years from diagnosis, age was strongly correlated with cognitive decline in H1 homozygotes but cognitive performance remained unchanged in H2 carriers, regardless of advancing age.