Decline of Fiber Tract Integrity Over the Adult Age Range: A Diffusion Spectrum Imaging Study

Purpose: We applied a novel diffusion spectrum imaging (DSI) acquisition to determine associations between aging and subcortical fiber tract integrity. Materials and Methods: We studied 35 cognitively healthy subjects (17 women), spanning the adult age range between 23 and 77 years, using anatomical MRI and a novel DSI acquisition scheme at 3 Tesla. The study was approved by the local institutional review board. DSI data were analyzed using tractography and complementary voxel-based analysis of generalized fractional anisotropy (GFA) maps. We determined the effects of age on generalized fractional anisotropy in selected fiber tracts as well as in a whole brain voxel-based analysis. For comparison, we studied the effects of age on regional gray and white matter volumes. Results: We found a significant reduction in anterior corpus callosum fiber tract integrity with age (P < 0.001), as well as significant GFA reduction throughout the subcortical white matter (P < 0.05, false discovery rate [FDR] corrected). GFA decline was accompanied by significant gray matter atrophy in frontal and temporal association cortex (P < 0.05, FDR corrected). Conclusion: Our data suggest that normal aging leads to a regionally specific decline in fiber tract integrity. DSI may become a useful biomarker in healthy and pathological aging.