PRKN and Parkinson disease: A follow-up study (Consortium on Risk for Early-Onset PD) examined the cognitive function in early-onset PD with the long-duration disease (>14 years) and found that Parkin carriers performed better on the Mini-Mental State Examination, clinical dementia ratings, attention, memory, and visuospatial performance than noncarriers (Alcalay et al., 2014).