SCD participants had significantly lower baseline Mini-Mental State Examination (MMSE, P < 0.001) and Preclinical Alzheimer’s Cognitive Composite (PACC, P < 0.001) scores, a significantly higher risk of AD dementia (P < 0.001), and significantly higher baseline plasma NfL levels (P = 0.04). Here, NEFL is linked to Schnyder corneal dystrophy.