Abstract Body: Introduction: To study the risk of incident dementia after a non-traumatic intracranial hemorrhage in a diverse US population, and evaluate if this risk is different among the subtypes of intracranial hemorrhage.

Methods: We performed a retrospective cohort study using both inpatient and outpatient claims data on Medicare beneficiaries between 2008 and 2018. The exposure was an incident diagnosis of non-traumatic intracranial hemorrhage, defined as a composite of intracerebral hemorrhage, subarachnoid hemorrhage, or subdural hemorrhage. The outcome was an incident diagnosis of dementia. The exposure and outcomes were identified using previously validated ICD-9 and ICD-10-CM diagnosis codes. In the primary analysis, we used Cox regression to study the risk of dementia after any intracranial hemorrhage, after adjusting for demographics and comorbidities. In secondary analyses, the risks of dementia in different subtypes of intracranial hemorrhage were studied.

Results: Among 2.1 million patients, 14,775 had a diagnosis of intracranial hemorrhage. During a median follow up of 5.6 years (IQR, 3.0-9.1), incident dementia was diagnosed in 2527 (17.1%) patients with an intracranial hemorrhage and 260,691 (12.8%) patients without. In adjusted Cox regression analysis, intracranial hemorrhage was associated with an increased risk of incident dementia (HR, 2.0; CI, 1.9-2.2). In secondary analyses, a higher risk of incident dementia was observed with intracerebral hemorrhage (HR, 2.4; CI, 2.2-2.5), subarachnoid hemorrhage (HR, 2.0; CI, 1.7-2.2), and subdural hemorrhage (HR, 1.6; CI, 1.4-1.7).

Conclusion: In a large, heterogeneous cohort of elderly US patients, we found that intracranial hemorrhage was independently associated with a 2-fold increased risk of incident dementia. This elevated risk was consistently observed across subtypes of intracranial hemorrhage.