BDNF and Alzheimer disease: Research has shown that NGF plays an important role in the occurrence and development of AD.6,7 Brain-derived neurotrophic factor (BDNF) that promotes neurons’ growth, differentiation, and survival has recently emerged as a potential diagnostic biomarker and a therapeutical molecule for AD.7 Both NGF and BDNF, therefore, have potential clinical value for staging, subtyping, or precision medicine for AD.6–8