COGNITIVE AND MOTOR FUNCTIONING IN PARKINSON DISEASE - SUBJECTS WITH AND WITHOUT QUESTIONABLE DEMENTIA

Background: The nature of cognitive performance in subjects with Parki nson disease (PD) without dementia is controversial, perhaps because o f failure to exclude subjects with unrecognized very mild dementia. Ob jective: To compare cognitive and motor functioning in well-characteri zed subjects with PD without overt dementia with healthy elderly contr ol subjects. Design: Subjects' conditions were evaluated clinically an d psychometrically at entry into a longitudinal study of cognitive and motor performance in elderly subjects. Measures included a global dem entia staging scale, the Washington University Clinical Dementia Ratin g; psychometric tests, including Logical Memory, Digit Span, Associate Learning, Information, Block Design, Digit Symbol, Trailmaking A, Cro ssing-off, Boston Naming Test, and Word Fluency; and motor measures, i ncluding finger tapping, gait velocity, reaction time, and movement ti me. Setting: A university-based research facility. Subjects: There wer e 3 groups of subjects: healthy elderly control subjects (n = 43), sub jects with PD without dementia (n = 58), and subjects with PD with que stionable dementia (n = 22), each evaluated at time of entry. Results: As expected, both PD groups were impaired on motor measures (gait vel ocity, finger tapping, and movement time) compared with the healthy el derly control group. Neither PD group showed slowing in reaction time. The subjects with PD with questionable dementia were more impaired on Logical Memory, Block Design, Digit Symbol, and Trailmaking A compare d with the subjects with PD without dementia. Although free of clinica lly evident cognitive dysfunction (Clinical Dementia Rating score, 0), the PD group without dementia was impaired with respect to the health y elderly control group on all measures from the psychometric assessme nt except Digit Span, Associate Learning, and Word Fluency. Conclusion s: The PD group without dementia showed global cognitive impairments i n comparison with the healthy elderly control group, possibly because the healthy elderly control subjects represented idealized aging. Alth ough the deficits were of small magnitude, this finding suggests that PD may predispose to subclinical cognitive impairment. Longitudinal fo llow-up is required to determine whether subjects with PD destined to develop overt dementia can be distinguished from those who do not.