NEFL and Alzheimer disease: Previous studies on the early detection of AD have been focused on the diagnostic utility of protein markers in the CSF and blood, and levels of NfL, amyloid-β (Aβ), and total tau (T-tau) are correlated with the cognitive function in individuals with AD (Agarwal and Tripathi, 2011; Haapalinna et al., 2018; Hampel et al., 2018).