Through the calculation of between-study heterogeneity in clinical AD samples, we found significant heterogeneity among studies on CHAT rs3810950 polymorphism in the allelic model (I2 = 74%), homozygous model (I2 = 72%), dominant model (I2 = 62%), and recessive model (I2 = 66%) and on CHAT rs2177369 polymorphism in the allelic model (I2 = 82%), homozygous model (I2 = 77%), and recessive model (I2 = 82%). Here, CHAT is linked to Alzheimer disease.