To identify the cause of high heterogeneity found in the comparison of CSF Ng levels between AD and healthy control, we performed subgroup analyses, and the results showed that the age-matched and age-mismatched, the MMSE ≥ 20 and MMSE < 20, the Ng ELISA and MSD analytical methods did not affect the heterogeneity (Supplementary Table S6 and Supplementary Figs. S4–S6). This evidence concerns the gene NRGN and Alzheimer disease.