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A Meta-analysis

Xuemei Huang, MD, PhD; Peter Chen, BS; Daniel I. Kaufer, MD; Alexander I. Tröster, PhD; Charles Poole, MPH, ScD

Arch Neurol. 2006;63:189-193.

Objective  To understand the relationship of apolipoprotein E (APOE) polymorphism to dementia in Parkinson disease (PD) because the APOE 4 allele is linked to Alzheimer disease.

Data Source  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.

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

Data Extraction  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.

Data Synthesis  Data analyses suggest publication bias and heterogeneity of source data for the 4 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 4 (95% confidence interval, 1.0-2.5); 1.3 for 2 (95% confidence interval, 0.73-2.4); and 0.54 for 3 (95% confidence interval, 0.18-1.6). The odds ratio estimates for 4 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 4 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.

Author Affiliations: Departments of Neurology (Drs Huang, Kaufer, and Tröster and Mr Chen) and Epidemiology (Dr Poole), University of North Carolina School of Medicine, Chapel Hill.

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