PPIB and Tremor: The cortical LP deposition and co-pathologies of the old-onset PD subtype may lead to faster clinical progression and a higher incidence of cognitive impairment than the early onset PD subtype, which is similar to the postural instability and gait-dominant PD subtype, and this has many more cortical Lewy bodies and amyloid-β plaques compared to the tremor-dominant PD subtype.