BACKGROUND: Carotid artery stiffness is associated with cerebrovascular disease (CeVD) and cognitive impairment, but evidence for its longitudinal effects on progression of CeVD and cognitive decline are limited. OBJECTIVES: To evaluate the longitudinal associations of carotid artery stiffness with CeVD progression, incident dementia, and cognitive decline. DESIGN: Longitudinal analyses from a memory-clinic cohort with a follow-up of 2 years. SETTING: A memory-clinic study. PARTICIPANTS: 194 participants (mean age=80, 63 % female) with or without cognitive impairments provided consent to take part in the study. MEASUREMENTS: Participants underwent carotid ultrasonography, brain MRI, and neuropsychological assessments were at baseline and follow-up. Carotid stiffness measures included ß-index, elastic modulus (Ep), and pulse wave velocity-ß (PWV-ß). CeVD markers included white matter hyperintensities (WMH), lacunes, cerebral microbleeds (CMBs) and cortical infarcts. Cognition was assessed with a neuropsychological battery. RESULTS: After 2 years, incident CeVD cases included lacunes (15.7 %), CMBs (23.8 %), and cortical infarcts (7.6 %). ß-index (ß=0.78, p <
0.001), Ep (ß=0.94, p <
0.001), and PWV-ß (ß=0.15, p = 0.003) were independently associated with WMH progression. Ep (ß=-0.15, p = 0.007) and PWV-ß (ß=-3.68, p = 0.007) were independently associated with visuomotor speed decline. No association was found with incident lacunes, CMBs or dementia. CONCLUSION: Carotid stiffness progression is associated with WMH progression and visuomotor speed decline.