Abstract Body: Introduction:
Cerebral amyloid angiopathy (CAA) is a significant cause of cerebrovascular disease and cognitive decline in elderly patients. There are limited population-based data regarding the prevalence of CAA and associated risks of mortality and incident cerebrovascular events.

Methods:
We performed a retrospective cohort study using inpatient and outpatient claims from 2008 to 2018 from a nationally representative 5% sample of Medicare beneficiaries. CAA and ischemic and hemorrhagic stroke were identified using previously validated ICD-10 codes. Mortality data was obtained from Medicare beneficiary files. We calculated prevalence of CAA during 2016-2018, and used Cox regression to examine the association of CAA with subsequent death and incident stroke after adjustment for demographics, vascular risk factors, and Charlson comorbidities.

Results:
Among 1,487,851 Medicare beneficiaries in our sample, 913 (0.06%) had a diagnosis of CAA during 2016-2018. In multivariable Cox regression analysis, there was no association between CAA and subsequent mortality (adjusted hazard ratio [aHR], 1.2; 95% CI, 0.7-1.9). Among 1,455,257 patients without prevalent stroke, including 355 of the CAA patients, there was a significant association between CAA and subsequent increased risk of any stroke (aHR, 6.3; 95% CI, 4.4-9.1), ischemic stroke (aHR, 2.5; 95% CI, 1.3-4.7), intracerebral hemorrhage (aHR, 32.1; 95% CI, 19.6-52.4), and subarachnoid hemorrhage (aHR, 9.5; 95% CI, 3.6-25.4) [Figure 1].

Conclusions:
In a nationally representative cohort of Medicare beneficiaries, the prevalence of clinically diagnosed CAA was approximately 6 per 10,000. CAA was not associated with an increased risk of mortality but was associated with an increased risk of incident stroke, both hemorrhagic and ischemic.