Journal of the International Neuropsychological Society



Course of cognitive decline in Parkinson's disease: A meta-analysis


DINO  MUSLIMOVIC  a1 c1 , BEN  SCHMAND  a1 a2 , JOHANNES D.  SPEELMAN  a1 and ROB J.  DE HAAN  a3
a1 Department of Neurology, Academic Medical Centre, University of Amsterdam, The Netherlands
a2 Department of Psychonomics, University of Amsterdam, The Netherlands
a3 Department of Clinical Epidemiology and Biostatistics, Academic Medical Centre, University of Amsterdam, The Netherlands

Article author query
muslimovic d   [PubMed][Google Scholar] 
schmand b   [PubMed][Google Scholar] 
speelman jd   [PubMed][Google Scholar] 
de haan rj   [PubMed][Google Scholar] 

Abstract

A meta-analysis was conducted on 25 longitudinal studies involving 901 initially non-demented Parkinson's disease (PD) patients to examine the magnitude of decline across multiple cognitive domains associated with disease progression. Pooled effect sizes reflecting the standardized difference between baseline and follow-up neuropsychological performance were calculated for 8 cognitive domains using a random-effects model. Relatively small effect sizes were found across all cognitive domains (d = .00 − .40). During a mean follow-up interval of 29 months, significant declines were detected in global cognitive ability (d = .40), visuoconstructive skills (d = .32), and memory (d = .29). Age showed a significant relation with decline in global cognitive ability and memory. Lower educational level was associated with greater decline in all cognitive domains. Studies with longer follow-up intervals yielded larger effect sizes for global cognitive ability. In non-demented PD patients, changes in cognitive functions over time appear to be modest. Educational level, age, and length of the follow-up interval are likely to affect the magnitude of decline in several domains. Methodological flaws, such as selection bias and uncontrolled practice effects, may have caused underestimation of the true extent of decline (JINS, 2007, 13, 920–932.)

(Received December 1 2006)
(Revised April 3 2007)
(Accepted April 17 2007)


Key Words: Parkinson's disease; Cognitive decline; Neuropsychological tests; Longitudinal studies; Prognosis; Meta-analysis.

Correspondence:
c1 Reprint requests to: D. Muslimovic, AMC Neurology, H2-222, PO Box 22660, 1100 DD Amsterdam, The Netherlands. E-mail: d.muslimovic@amc.uva.nl


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