Non-Traumatic Intracranial Hemorrhage and Risk of Incident Dementia in U.S. Medicare Beneficiaries

Background: 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 for the subtypes of intracranial hemorrhage. Methods: We performed a retrospective cohort study using both inpatient and outpatient claims data on Medicare beneficiaries between January 1, 2008 and December 31, 2018. The exposure was a new diagnosis of non-traumatic intracranial hemorrhage, defined as a composite of intracerebral hemorrhage (ICH), subarachnoid hemorrhage (SAH), and subdural hemorrhage (SDH). The outcome was a first-ever diagnosis of dementia. The exposure and outcomes were identified using validated ICD-9 and ICD-10-CM diagnosis codes. We excluded patients who had prevalent intracranial hemorrhage or dementia, to ensure that only incident cases were counted in our analyses. In the primary analysis, we used Cox regression to study the risk of dementia after 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%) in those without intracranial hemorrhage. The cumulative incidence rate of dementia was 8.6% (IQR, 8.1-8.9) among patients with an intracranial hemorrhage, and 2.2% (2.0-2.4) in patients without intracranial hemorrhage. 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 ICH (HR, 2.4; CI, 2.2-2.5), SAH (HR, 1.99; CI, 1.7-2.2), and SDH (HR, 1.6; CI, 1.4-1.7). Conclusion: In a large heterogeneous cohort of elderly US participants, 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.