Association between α1-antichymotrypsin signal peptide -15A/T polymorphism and the risk of Alzheimer's disease: a meta-analysis.

No consensus has been recently reached at the relationship between the α1-antichymotrypsin (ACT) signal peptide -15A/T polymorphism and Alzheimer’s disease (AD) risk. Thus, our study aimed to better assess this association by performing a meta-analysis, including 4,212 cases and 4,039 controls from 29 studies. Odds ratios (ORs) with the 95% confidence interval (CI) were used to assess the strength of relationship between ACT -15A/T polymorphism and AD risk. Overall, a borderline statistically significant association was detected under recessive model comparison in all subjects (AA vs. AT+TT: OR 1.12, 95% CI 1.01-1.25, P = 0.04). But in subgroup analysis by ethnicity, no significant association was found in Caucasians, Asians, or Africans. Moreover, after exclusion of one study which affect the heterogeneity, the ACT A allele and AA genotype were statistically associated with late-onset AD (LOAD) risk (AA vs. TT: OR 1.25, 95% CI 1.06-1.48, P = 0.007, A vs. T: OR 1.12, 95% CI 1.03-1.21, P = 0.008), especially in Caucasians. In conclusion, our study suggests that the common α1-antichymotrypsin signal peptide -15A/T polymorphism may not be a major risk factor for AD. However, the polymorphism is capable of increasing LOAD risk.