Microstructural differences in white matter tracts across middle to late adulthood: a diffusion MRI study on 7167 UK Biobank participants

White matter fiber tracts demonstrate heterogeneous vulnerabilities to aging effects. Here, we estimated age-related differences in tract properties using UK Biobank diffusion magnetic resonance imaging data of 7167 47- 76-year-old neurologically healthy people (3368 men and 3799 women). Tract terms generalized fractional anisotropy, axial diffusivity, radial mean diffusivity were sampled on 76 tracts; for each tract, by fitting these indices against age a linear model. This cross-sectional study demonstrated 4 age-difference patterns. The dominant pattern was lower anisotropy higher with age, constituting 45 tracts, mostly involving the association, projection, commissure fibers connecting prefrontal lobe. other 3 patterns constituted only 14 atypical indices, mainly involved parietal, occipital, temporal cortices. By analyzing large volume available from Biobank, has provided detailed description over whole brain which generally supports myelodegeneration hypothesis.