Abstract
Aging is known to have deleterious effects on cerebral white matter, yet little is known about these white matter alterations in advanced age. In this study, 94 oldest-old adults without dementia (90–103 years) underwent diffusion tensor imaging to assess relationships between chronological age and multiple measures of integrity in 18 white matter regions across the brain. Results revealed significant age-related declines in integrity in regions previously identified as being sensitive to aging in younger-old adults (corpus callosum, fornix, cingulum, external capsule). For the corpus callosum, the effect of age on genu fractional anisotropy was significantly weaker than the relationship between age and splenium fractional anisotropy. Importantly, age-related declines in white matter integrity did not differ in cognitively normal and cognitively impaired not demented oldest-old, suggesting that they were not solely driven by cognitive dysfunction or preclinical dementia in this advanced age group. Instead, white matter in these regions appears to remain vulnerable to normal aging processes through the 10th decade of life.
Highlights
Aging is known to have deleterious effects on cerebral white matter
The current study examined age-related differences in white matter integrity in oldest-old adults without dementia and assessed whether these relationships differed between cognitively normal and cognitively impaired not demented (CIND) subgroups
Observed age-related declines in white matter integrity overlapped with regions previously identified as showing additional declines in younger-old adults with, or at risk for, dementia
Summary
Aging is known to have deleterious effects on cerebral white matter (for reviews see Gunning-Dixon et al, 2009; Raz and Rodrigue, 2006; Salat, 2011). Multiple diffusion indices can be calculated to assess the degree of restricted diffusion (fractional anisotropy, FA), rate of overall diffusion (mean diffusivity, MD), and the rate of diffusion parallel (axial diffusivity, AD) and perpendicular (radial diffusivity, RD) to the primary diffusion direction. These measures are thought to approximate the “integrity” of white matter because they are sensitive to numerous properties of the underlying microstructure (e.g., axonal size and density, degree of myelination, and coherence of fiber orientation) that differ across individuals and with aging
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