Several case–control studies have now been undertaken to examine the association of the common allelic variants (ε2, ε3, ε4) of the apoE gene with AMD. These studies have concentrated on white individuals from mainly European backgrounds,
20 21 22 23 24 25 although one study has been undertaken in ethnic Chinese.
26 Only three of the seven previous studies have shown a significant protective effect for the apoE ε4 allele with late (end-stage) AMD (odds ratio [OR] 0.16, 95% confidence interval [CI] 0.05–0.43
20 ; OR 0.43, 95% CI 0.21–0.88
21 ; and a pooled study OR 0.54, 95% CI 0.41–0.70,
24 ), whereas the protective nature of this allele was more modest in two other studies (OR 0.88, 95% CI 0.58–1.35
22 ; and OR 0.4, 95% CI 0.1–1.2
23 ). In individuals of Chinese ethnicity, there was little evidence to suggest an involvement of the ε4 allele of this gene in AMD (OR 0.83, 95% CI 0.23–2.53).
26 In the studies in which association was identified with the ε4 allele, the findings were inconsistent, with protection being found when both exudative or atrophic disease were pooled,
21 24 or when only exudative disease was analyzed,
20 or in individuals with familial disease who were younger than 70 years.
22 In addition, these studies had a small number of individuals carrying the ε4 allele, and that limited the investigators’ ability to perform disease subanalysis. Three of the studies also suggested that the ε2 allele may increase the risk of AMD, although none of these reached statistical significance.
21 23 24