Specifically, post hoc analyses showed that compared to controls, mean NPTX2 levels were 0.5-fold in sporadic AD (− 491 pg/ml, 95% CI −280 to − 702; adj.p < 0.0001), 0.6-fold in aDS (− 400 pg/ml, 95% CI − 196 to − 604; adj.p < 0.0001), 0.5-fold in pDS (− 472, 95% CI − 208 to − 736; adj.p < 0.0001) and 0.3-fold in dDS (− 595, 95% CI − 361 to − 828; adj.p < 0.0001). This evidence concerns the gene NPTX2 and Alzheimer disease.