title: Apolipoprotein ε4-allele as a significant risk factor for conversion from mild cognitive impairment to Alzheimer's disease: a meta-analysis of prospective studies.
abstract: Recent studies of the relationship between progression from mild cognitive impairment (MCI) to Alzheimer disease (AD) and APOE ε4-allele revealed inconsistent results. To estimate the risk posed by APOE ε4-allele for developing AD in MCI subjects using meta-analysis and identify possible sources of heterogeneity between studies, we reviewed longitudinal epidemiological studies of the presence of APOE ε4-allele on risk for progression to dementia in MCI subjects, and conducted meta-analyses of the results from these studies. Our study was derived from 315 positive-outcome events and 461 negative-outcome events from 8 prospective studies. The pooled RR was statistically significant (pooled RR = 2.09; 95 % CI, 1.52-2.88). The Q statistics indicated high heterogeneity across studies (Q = 14.21, p = 0.003). RR were significantly related to the ethnicity of the sample (z = 3.58, p = 0.024). No significant heterogeneity was observed after stratification in four European-population studies (χ² = 0.67, p = 0.880), but it remained in four American-population studies (χ² = 18.52, p = 0.003). Heterogeneity markedly reduced after excluding one specific study (Q = 4.9, p = 0.009; I² = 39 %). APOE ε4-allele conferred increased risk for progression to dementia in MCI subjects. Ethnicity is a critical factor to yield heterogeneity. Further studies using larger sample sizes are required.
authors.affiliation: Department of Epidemiology, School of Public Health, Tianjin Medical University, Tianjin, China. mf2002245mf@yahoo.com.cn
authors.forename: Ma
authors.initials: M
authors.lastname: Fei
authors.forename: Wang
authors.initials: W
authors.lastname: Jianhua
mesh_terms: D000368:Aged; D000483:Alleles; D000544:Alzheimer Disease / Q000235:genetics*; D001057:Apolipoproteins E / Q000235:genetics*; D060825:Cognitive Dysfunction / Q000235:genetics*; D005260:Female; D018740:Genetic Heterogeneity; D006801:Humans; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors
chemical_list: D001057:Apolipoproteins E