To determine whether extra-cranial carotid artery disease (ECAD) increases risk of Alzheimer’s Disease (AD).

The role of extra-cranial carotid artery disease (ECAD) in AD is not clear. Treatments including carotid endarterectomy (CEA) are available and may add to dementia and neurodegenerative disease prevention efforts.

This retrospective cohort study used the Symphony claims dataset from 2007 to 2017. Patient claims records were surveyed for a diagnosis of AD starting 6 months post ECAD diagnosis for the duration of enrollment in the claims database.  The Symphony dataset contains claims from private-payer and Medicare insurance datasets from across the United States. Patients diagnosed with ECAD were identified. Survival analysis was used to determine the association between ECAD and diagnosis of NDD in the post index date follow-up period. A propensity score approach was used to minimize measured and unmeasured selection bias.

Chi squared analysis was used to test for statically significant differences in incidence of AD between patients with and without ECAD.

In this cohort study of 192,556 propensity score matched patients with and without ECAD exposure was associated with subsequent decrease in diagnosis of neurodegenerative disease, most specifically Alzheimer’s disease (RR, 1.223; 95%CI, 1.166 to 1.282; P < .0001).

Outcomes of these analyses provide proof of concept indicating the impact of ECAD on AD.  These outcomes provide a foundation on which to test hypotheses regarding the mechanisms contributing to ECAD associated AD. Follow up in underway to investigate the effect of CEA and ECAD-related treatment such as stent placement to evaluate their protective effect.