P3 latency change in aging and Parkinson disease

H. Tachibana, K. Aragane, K. Kawabata and M. Sugita
Fifth Department of Internal Medicine, Hyogo College of Medicine, Nishinomiya, Japan.

OBJECTIVE: To evaluate whether age-related slowing of mental processing assessed by event-related potentials is more prominent in patients with Parkinson disease (PD) than in age-matched control subjects. DESIGN: Consecutive case series of patients with PD and an age-matched control group. SETTING: A university hospital in Nishinomiya, Japan. STUDY PARTICIPANTS: Twenty-eight nondemented patients with PD and 28 age-matched control subjects. MAIN OUTCOME MEASURES: The P3 component of the event-related potentials was elicited during a visual semantic discrimination task. The relation of the P3 latency and the reaction time (RT) to age within each group was evaluated using correlation and regression analysis. The relationship among the P3 latency, the RT, and age was also assessed by dividing both groups into younger (age < 60 years) and older (age > or = 60 years) subgroups. RESULTS: The P3 latency and the RT of patients with PD were significantly longer than those of the control subjects (P < .01 and P < .02, respectively). There was a significant correlation between the P3 latency and age in both the parkinsonian and control groups (P < .01 and P < .05, respectively). The slope (b = 3.54 ms/y) of the P3 latency vs age was steeper among the patients with PD than among the control subjects (b = 1.66 ms/y) at the Pz site. The P3 latency in the older parkinsonian group (n = 16) was significantly prolonged compared with that in the older control group (n = 16) (P < .01), while no difference was found between the younger patients (n = 12) and the younger control group (n = 12). Similar trends were found for the RTs (P < .05). Neither the P3 latency nor the RT was correlated with any variable (eg, medication, mental status, illness duration, or motor disability). CONCLUSION: The results provide evidence that patients with PD experience excessive cognitive slowing with advancing age.