Quantitative multi-modal MRI of the hippocampus and cognitive ability in community-dwelling older subjects

Hippocampal structural integrity is commonly quantified using volumetric measurements derived from brain magnetic resonance imaging (MRI). Previously reported associations with cognitive decline have not been consistent. We investigate hippocampal integrity using quantitative MRI techniques and its association with cognitive abilities in older age. Participants from the Lothian Birth Cohort 1936 underwent brain MRI at mean age 73 years. Longitudinal relaxation time (T1), magnetization transfer ratio (MTR), fractional anisotropy (FA) and mean diffusivity (MD) were measured in the hippocarnpus. General factors of fluidtype intelligence (g), cognitive processing speed (speed) and memory were obtained at age 73 years, as well as childhood IQ test results at age 11 years. Amongst 565 older adults, multivariate linear regression showed that, after correcting for ICV, gender and age 11 IQ larger left hippocampal volume was significantly associated with better memory ability (beta = .11,p = .003), but not with speed or g. Using quantitative MRI and after correcting for multiple testing, higher Ti and MD were significantly associated with lower scores of g (beta range = -.11 to -.14, p < .001), speed (beta range = -.15 to -.20, p < .001) and memory (beta range = -.10 to -.12, p < .001). Higher MTR and FA in the hippocampus were also significantly associated with higher scores of g (beta range = .17 to .18, p < .0001) and speed (beta range = .10 to .15, p < .0001), but not memory.

An open access version is available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3979658/