PROJECT SUMMARY Our parent award is designed as a prospective, observational study to understand the role of extracranial carotid artery disease (ECAD) in Alzheimer’s disease and related dementias (ADRD) risk. One of the Aims is to evaluate the effects of treatment of ECAD using carotid endarterectomy on ADRD risk. This work involves evaluation of key blood-based and MRI-defined biomarkers associated with neurodegeneration and ADRD. These biomarkers are evaluated longitudinally in subjects with ECAD, subjects without ECAD (controls) and subjects with ECAD who have surgery. Improved safety profiles of carotid artery stenting as treatment for ECAD has led to significant increases in this procedure. Using this cohort of patients who have ECAD and undergo carotid stenting, this Supplemental award will evaluate whether carotid stenting (which leaves the plaque in place and has been associated with increased microemboli) affects biology and biomarkers associated with ADRD risk.