Mean plasma NFL level was 32.9 ± 25.5 pg/ml in AD patients, 20.0 ± 7.3 pg/ml in MCI patients, 15.4 ± 9.9 pg/ml in PDND patients, 23.3 ± 10.8 pg/ml in PDD patients, and 17.8 ± 6.4 pg/ml in controls. Here, NEFL is linked to Alzheimer disease.