MRI phenotypes of the brain are related to long‐term dementia outcome in community‐dwelling older adults

Abstract

AbstractBackgroundIndividual brain MRI markers only show at best a modest association with long‐term occurrence of dementia. Therefore, it is challenging to accurately identify individuals at increased risk for dementia. We aimed to identify different brain MRI phenotypes by combined hierarchical clustering analysis based on neurodegenerative and neurovascular brain MRI markers in community‐dwelling individuals. Within each of these brain MRI phenotype subgroups, we determined the long‐term dementia risk.MethodA hierarchical clustering analysis based on combined brain MRI markers in community‐dwelling individuals of the Age‐Gene/Environment Susceptibility (AGES) Reykjavik Study (n = 3056) was applied to identify different brain MRI phenotypes. Brain MRI markers used in the hierarchical clustering analysis were brain volumes for the estimation of brain atrophy, WMH markers (volume and shape), brain infarcts, microbleeds, and enlarged perivascular spaces.ResultWe identified 14 distinct subgroups of individuals with different brain MRI phenotypes (figure 1 and figure 2). The brain MRI phenotypes of the subgroups ranged from limited burden (subgroup (S) 12), mostly atrophy and infarcts (S14), mostly irregularly shaped WMH and atrophy (S3) to a multi‐burden subgroup (S2). These subgroups had a different long‐term risk for dementia (mean time to follow‐up: 9.9 ± 2.6 years; hazard ratio ranging from 4.1 (95%‐CI: 3.19‐13.40) to 13.8 (95%‐CI: 4.28‐44.37); see figure 3); especially the multi‐burden brain MRI phenotype showed an increased risk compared to the reference group (HR: 13.8 (95%‐CI: 4.28‐44.37)).ConclusionOur results indicate that distinct brain MRI phenotypes are related to different long‐term risks of developing dementia. Brain MRI phenotypes may assist in an improved understanding of the structural correlates of dementia predisposition. These findings may in the future be useful to determine patient prognosis and may aid in patient selection for future treatment studies.