Apolipoprotein E and dementia in Parkinson disease: a meta-analysis.
OBJECTIVE
To understand the relationship of apolipoprotein E (APOE) polymorphism to dementia in Parkinson disease (PD) because the APOE epsilon4 allele is linked to Alzheimer disease.


METHODS
We reviewed MEDLINE, BIOSIS Previews, and ISI Web of Science from January 1, 1966, to May 7, 2004, supplemented by citation analysis from retrieved articles.


METHODS
Case-control studies using clinical or pathologic criteria for PD and dementia, and with complete APOE genotype frequencies data.


METHODS
We compared estimated prevalence odds ratios for dementia in PD in relation to each allele. We also looked for evidence of heterogeneity and publication bias and performed a stratified analysis on several study characteristics.


RESULTS
Data analyses suggest publication bias and heterogeneity of source data for the epsilon4 allele (homogeneity P = .2; Begg and Mazumdar, P = .06; and Egger et al, P = .1). The estimated odds ratios for development of dementia in PD are 1.6 for epsilon4 (95% confidence interval, 1.0-2.5); 1.3 for epsilon2 (95% confidence interval, 0.73-2.4); and 0.54 for epsilon3 (95% confidence interval, 0.18-1.6). The odds ratio estimates for epsilon4 were higher for studies published in 1996 or later (2.3 vs 1.0) and for studies conducted outside North American sites (2.4 vs 1.2).


CONCLUSIONS
The APOE epsilon4 allele appears to be associated with a higher prevalence of dementia in PD. Publication bias and heterogeneous source data may, however, confound this conclusion. Confirmatory studies that use standardized and validated diagnostic criteria for dementia in PD are needed.
Department of Neurology, University of North Carolina School of Medicine, Chapel Hill 27599-7025, USA. xuemei@med.unc.edu
Xuemei
X
Huang
Peter
P
Chen
Daniel I
DI
Kaufer
Alexander I
AI
Tröster
Charles
C
Poole
D001057:Apolipoproteins E / Q000235:genetics*; D016022:Case-Control Studies; D003704:Dementia / Q000235:genetics*; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D016017:Odds Ratio; D010300:Parkinson Disease / Q000235:genetics*
D001057:Apolipoproteins E