In this present study, we mainly investigated the effects of CSF GAP-43 on cognitive impairment and whether the roles of GAP-43 were related to APOE ε4 status among cognitively normal (CN) controls, MCI and AD participants from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database. This evidence concerns the gene APOE and early-onset autosomal dominant Alzheimer disease.