Notably, most major risk factors of PDD in the model have been found to correlate either with the underlying core pathology of Parkinson disease (i.e. striatal, including caudate DAT deficits and hyposmia are correlated with nigrostriatal degeneration and the spread of α-synuclein) or with Alzheimer disease co-pathology (which is correlated with low Aβ42 in CSF).46–48 Our findings therefore point to these general classes of neurodegenerative disease pathologies as main drivers of cognitive impairment in Parkinson disease. The gene discussed is SLC6A3; the disease is Alzheimer disease.