Individual variation in brain microstructural-cognition relationships in aging
Raihaan Patel, Clare E. Mackay, Michelle G. Jansen, Gabriel A. Devenyi, M. Clare O’Donoghue, Mika Kivimäki, Archana Singh-Manoux, Enikő Zsoldos, Klaus P. Ebmeier, M. Mallar Chakravarty, Sana Suri. Preprint February 2021
While all individuals are susceptible to age-related cognitive decline, significant inter- and intra-individual variability exists. However, the sources of this variation remain poorly understood. Here, we examined the association between 30-year trajectories of cognitive decline and multimodal indices of brain microstructure and morphology in older age. We used the Whitehall II Study, an extensively characterised cohort using 3T brain magnetic resonance images acquired at older age (mean age = 69.52 ± 4.9) and 5 repeated cognitive performance assessments between mid-life (mean age = 53.2 ± 4.9 years) and late-life (mean age = 67.7 ± 4.9). Using non-negative matrix factorization, we identified 10 brain microstructural components that integrate measures of cortical thickness, surface area, fractional anisotropy, and mean and radial diffusivities. We observed two modes of variance that describe the association between cognition and brain microstructure. The first describes variations in 5 microstructural components associated with low mid-life performance across multiple cognitive domains, decline in reasoning abilities, but a relative maintenance of lexical and semantic fluency from mid-to-late life. The second describes variations in 5 microstructural components that are associated with low mid-life performance in lexical fluency, semantic fluency and short-term memory performance, but a retention of abilities in multiple domains from mid-to-late life. The extent to which a subject loads onto a latent variables predicts their future cognitive performance 3.2 years later (mean age = 70.87 ± 4.9). This data-driven approach highlights a complex pattern of brain-behavior relationships, wherein the same individuals express both decline and maintenance in function across cognitive domains and in brain structural features.
Significance Statement Although declines in cognitive performance are an established aspect of aging, inter- and intra-individual variation exists. Nevertheless, the sources of this variation remain unclear. We analyse a unique sample to examine associations between 30-year trajectories of cognitive decline and multimodal indices of brain anatomy in older age. Using data-driven techniques, we find that age-related cognitive decline is not uniform. Instead, each individual expresses a mixture of maintenance and decline across cognitive domains, that are associated with a mixture of preservation and degeneration of brain structure. Further, we find the primary determinants of late-life cognitive performance are mid-life performance and higher brain surface area. These results suggest that early and mid-life preventative measures may be needed to reduce age-related cognitive decline.