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Abstract
Background: The Glu298Asp gene polymorphism in NOS3 gene has been extensively investigated for association to Alzheimer's disease (AD), however, results of different studies have been inconsistent. The objective of this study is to assess the relationship of NOS3 Glu298Asp polymorphism and AD risk by using meta-analysis. Methods: All eligible case–control studies were searched in PubMed and Embase. Odds ratios (OR) with the 95% confidence intervals (CI) were used to assess the association. Results: A total of 5522 cases and 4877 controls in 20 case–control studies were included. Obvious heterogeneity among studies was detected, and no significant association was observed between the NOS3 Glu298Asp polymorphism and AD risk. After exclusion of three studies, the heterogeneity disappeared and still no association was observed. In the subgroup analysis by ethnicity, we did not find any significant association between this polymorphism and AD risk in both Asians and Caucasians. Conclusions: This meta-analysis suggested that the NOS3 Glu298Asp gene polymorphism is not a strong risk factor for AD. To further evaluate gene-to-gene and gene-to-environmental interactions between polymorphisms of NOS3 gene and AD risk, more studies with large groups of patients are required.