Association of Apolipoprotein E polymorphism in Alzheimer's Disease in Indian population- A meta analysis

INTRODUCTION:  Alzheimer’s disease (AD) is the most common form of dementia, estimated to be affecting 4.4% of the population over 65 years of age. Apo E ε4 allele is a known genetic risk factor for AD which not only predisposes and influences the severity of pathological changes in the brain, thereby modifying the age at onset, but also promotes cognitive decline early in non-demented older people. The objective of study,  to review and analyse the published evidence on Apo E polymorphism with the susceptibility to AD and frequency of Apo E ε4 genotype and homozygotes among patients diagnosed with AD as compared to controls in Indian Population

METHODS:  In the present study, MEDLINE was reviewed for articles published till June, 2013 supplemented by citation analysis from retrieved articles to select case control studies. A meta-analysis was performed to demonstrate the association of ApoE gene with AD by random effects models. The association was assessed by pooled MH odds ratio  with 95% confidence intervals

RESULTS:  A total of 07 studies representing data from 417 AD patients and 651controls in the Indian population were eligible. ApoE Ɛ2/4, Ɛ3/4 and Ɛ4/4 genotypes (OR = 3.93, 95% CI: 1.60 - 9.68; OR = 4.18, 95% CI: 2.54 - 6.87; OR = 4.81, 95% CI: 1.95 - 11.86) as well as ApoE Ɛ4 allele (OR = 5.90, 95% CI: 3.44 – 10.13) were associated with an increased risk AD whereas, ApoE Ɛ2/3, Ɛ3/3 genotypes and ApoE Ɛ3 (OR= 0.52, 95% CI: 0.32 - 0.83; OR = 0.28, 95% CI: 0.19 - 0.42; OR = 0.29, 95% CI: 0.17-0.50) were found to be significant marginal protective factors for AD

CONCLUSIONS: These results indicate that all genotypes of Apo E ε4 allele are associated with an increased risk of AD, whereas genotypes Apo E ε2 allele are protective against AD