Abstract
OBJECTIVES: Recently, several meta-analyses have reported an association between interleukin (IL) gene polymorphisms and the risk of Alzheimer's disease (AD). Several further papers discussing the relationship with the risk of AD have recently been published. The aim of this meta-analysis was to re-evaluate and update the associations between IL gene polymorphisms and the risk of AD. METHODS: The search sources were PubMed, Science Direct, Scopus, and Google Scholar up to July 2015, and the following search terms were used: "interleukin 1 or interleukin 6 or interleukin 10" and "variant or polymorphism or SNP" in combination with "Alzheimer's disease". A meta-analysis using the pooled odds ratios and 95% confidence intervals was carried out to assess the associations between four polymorphisms of IL genes (- 889C > T in IL-1α, - 511C > T in IL-1β, - 174G > C in IL-6 and - 1082G > A in IL-10) and the risk of AD under the heterozygous, homozygous, dominant, and recessive models with fixed- or random-effects models. RESULTS: A total of 21,864 cases and 40,321 controls from 93 individual studies were included in this meta-analysis. Our results indicated that the - 889C > T polymorphism was strongly associated with the increased risk of AD. However, three polymorphisms were not associated with the risk of AD. CONCLUSIONS: Similar to previous meta-analyses, our updated meta-analysis suggested that the - 889C > T polymorphism may be a factor in AD. However, the results of our meta-analysis of the - 174G > C polymorphism differed from those of previous meta-analyses. Consequently, we suggest that the - 174G > C polymorphism may not be a risk factor for AD.