Premotor cognitive status in a cohort of incident Parkinson disease patients (NEDICES)

Background: A variety of symptoms may precede the classical motor features of Parkinson disease (PD). However, it is not known whether cognitive dysfunction precedes the motor phase of PD. We examined whether patients with incident PD had had global cognitive function disturbances three years prior to diagnosis when compared with matched controls in a cohort of community-dwelling subjects. Methods: All participants were age 65 years or older (median 76 years) and were enrolled in the Neurological Disorders in Central Spain (NEDICES) study in central Spain. We identified all participants with incident PD (N = 23), diagnosed in the follow-up examination (1997-1998), who had performed an expanded 37-item version of the Mini-Mental State Examination (37-MMSE) at the baseline evaluation (1994-1995). These 23 were 1:4 matched to 92 controls. Results: Baseline 37-MMSE scores were 27.9 ± 4.9 (28) in PD patients and 28.7 ± 6.5 (31) in controls (p = 0.212). There were no patient-control differences in orientation, immediate recall, attention and calculation, memory recall, language, or visuospatial copying. In analyses that adjusted for several possible confounding factors, there were no case-control differences. Conclusions: In this population-based sample, patients with incident PD did not have evidence of significant global cognitive function disturbances three years prior to their diagnosis when compared with matched controls. Our data suggest that global cognitive dysfunction does not precede the diagnosis of PD.