Results from the one-sample t-test indicated that the mean NfL concentration in the CN+, MCI, and AD groups was significantly greater than the normal cutoff of 35.02 pg/mL (NfL in CN + group = 39.34, P = 0.015; NfL in MCI group = 41.9, P<0.001; NfL in AD group = 45.06, P<0.001). Here, NEFL is linked to Alzheimer disease.