Journal of the International Neuropsychological Society

Research Articles

Neurocognitive Speed and Inconsistency in Parkinson's Disease with and without Incipient Dementia: An 18-Month Prospective Cohort Study

Cindy M. de Friasa1 c1, Roger A. Dixona2 and Richard Camiciolia3a4

a1 School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, Texas

a2 Department of Psychology, University of Alberta, Edmonton, Alberta, Canada

a3 Division of Neurology, University of Alberta, Edmonton, Alberta, Canada

a4 Glenrose Rehabilitation Hospital, Edmonton, Alberta, Canada

Abstract

We examined two-wave longitudinal changes in two indicators of neurocognitive speed (i.e., mean rate, intraindividual variability) using one simple and three complex reaction time tasks. Participants included idiopathic Parkinson's disease (PD) patients, with and without incipient dementia, and normal controls. At baseline, there were 45 patients (26 men, 19 women) with idiopathic PD who ranged from 65 to 84 years (M = 71.3; SD = 4.5) and 47 matched controls (27 men, 20 women) who ranged from 65 to 84 years (M = 71.4; SD = 4.9). The 18-month longitudinal sample comprised of 74 returning participants (43 controls; 31 PD patients) who had no cognitive impairment or dementia at both waves. Ten of the 31 PD patients returning for Time 3 had dementia or cognitive impairment. These constituted the PD with incipient dementia (PDID) group. Repeated measures analyses of variance showed that the PD and PDID groups were slower over time on the reaction time tasks, whereas the controls improved their performance over time on all tasks. Inconsistency distinguished the two clinical groups (i.e., the PDID group but not the PD group became more inconsistent over time). Changes in neurocognitive speed and inconsistency may be valid clinical markers of PDID. (JINS, 2012, 18, 1–9)

(Received May 23 2011)

(Revised March 01 2012)

(Accepted March 05 2012)

Correspondence:

c1 Correspondence and reprint requests to: Cindy M. de Frias, School of Behavioral and Brain Sciences, The University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080. E-mail: cdefrias@utdallas.edu