EGF and depressive symptom measurement: Of 17 candidate biomarkers, eight (UPDRS-III, MODHY, depression, CSF Aβ42, CSF t-tau, CSF p-tau, plasma EGF, SPARE-AD) had been previously shown to associate cross-sectionally (vs. longitudinally) with baseline cognition in either PD or AD [15,23,25,28].