NfL levels were significantly different between SCD A− and MCI A− (12.28 ± 2.36 vs 16.60 ± 5.47, p = 0.002, η2 = 0.31), between SCD A + and MCI A + (16.11 ± 6.60 vs 25.01 ± 12.27, p = 0.020, η2 = 0.14), between MCI A + and MCI A− (25.01 ± 12.27 vs 16.60 ± 5.47, p = 0.005, η2 = 0.18), and between AD and MCI A− patients (24.54 ± 7.01 vs 16.60 ± 5.47 p < 0.001, η2 = 0.37). Here, SCD is linked to Alzheimer disease.