NEFL and Mental deterioration: We aimed here to investigate how plasma GFAP, NfL, p‐tau181, and Aβ42/40 are associated with (1) performance on five cognitive domains at baseline, (2) cognitive decline on five cognitive domains over a 2‐year follow‐up period, and (3) functional independence in activities of daily living (ADL) at baseline, all across and within multiple neurodegenerative and cerebrovascular diseases.