Population-based case-control study of cognitive function in early Parkinson's disease (NEDICES)

In this population-based sample of older patients with early PD, the rate of subjective and object cognitive impairment was appreciable. Patients with PD of less than five years duration performed relatively poorly on tests of global cognition, verbal fluency and memory. Clinicians should be vigilant to these cognitive difficulties even in the early stages of PD.