To assess the association of infratentorial cerebral microbleeds (CMBs) and incident dementia

Subcortical CMBs are common in older adults and linked to hypertensive small vessel disease. Infratentorial CMBs are similarly associated with hypertension, but their importance regarding dementia risk is less clear. This study investigates the impact of infratentorial CMBs on incident dementia in the community-based, longitudinal Atherosclerosis Risk in Communities-Neurocognitive Study (ARIC-NCS).

Participants (aged 67-90) without intracerebral hemorrhage or dementia (in 2011-13) were included. CMBs were identified and categorized by location from T2*GRE sequences as follows: subcortical, infratentorial, and lobar CMBs, and superficial siderosis. Incident dementia diagnoses were determined through in-person cognitive testing, informant interviews, and hospital records. Cox proportional-hazards models assessed the association between infratentorial CMB presence (vs absence) and frequency (regardless of other concurrent CMB type), each with incident dementia through 2021. Models adjusted for demographics, vascular risk factors, and other imaging markers of small vessel disease.

Among 1574 participants, 303 had CMBs. 69 of these had at least one infratentorial CMB. The presence of infratentorial compared to no infratentorial CMBs was associated with incident dementia in demographic- and vascular risk factor-adjusted models (HR 1.72 [95% CI 1.16-2.55]) but was attenuated after additional adjustment for white matter hyperintensities (HR 1.45 [95% CI 0.97-2.17]). Compared to those with no infratentorial CMBs, the risk of dementia was nonsignificantly elevated in participants with 1 infratentorial CMB (adjusted HR 1.34 (0.83, 2.14) but significantly elevated in those with ≥2 infratentorial CMBs (HR 2.13 [95% CI 1.10-4.11]), compared to individuals with no infratentorial CMBs .

A greater number of infratentorial CMBs is associated with an increased risk of incident dementia in this community-based cohort. Future studies should evaluate the potential etiology of this association and how infratentorial CMBs in combination with other CMB patterns may alter dementia risk.