Department of Radiology, University of Tokyo, Bunkyo-ku, Tokyo, Japan.
AJNR Am J Neuroradiol. 2011 Dec;32(11):2103-9. doi: 10.3174/ajnr.A2785. Epub 2011 Oct 13.
DTI provides a sensitive measure of change in the microstructure of white matter integrity. The purpose of our study was to investigate age-related changes, sex differences, and age-by-sex interactions in white matter integrity (FA, AD, and RD) across the whole brain with a large sample.
A total of 857 healthy subjects (mean age = 56.1 ± 9.9 years; age range = 24.9-84.8 years) were included in this study. All subjects were scanned at 3T. With use of TBSS, we examined the effects of age and sex on FA, AD, and RD in the white matter.
Global FA was negatively correlated with age (R(2) = 0.18, P < .0001), and global AD and RD were positively correlated with age (AD: R(2) = 0.02, P < .0001; RD: R(2) = 0.19, P < .0001). The correlation between age and global AD, however, was weak. Voxelwise analysis revealed a number of regions where FA was negatively correlated with age, with most of these regions showing a significant positive correlation between RD and age. There was a significant age-related FA increase in several white matter regions. Voxelwise analysis also revealed many regions where FA, AD, or RD differed between men and women; however, no region showed a significant interaction between age and sex.
Our results suggest that age-related changes in white matter integrity are more strongly associated with myelin sheath degeneration than with axonal degeneration, and that, in some specific regions, the number of remyelinated axons might increase with age. Our results also suggest that there are no sex differences in the aging process of the white matter.
DTI 提供了对大脑白质微观结构完整性变化的敏感测量。我们的研究目的是用大样本量来探究大脑白质整体的完整性（FA、AD 和 RD）在年龄相关性变化、性别差异和年龄-性别交互作用。
本研究共纳入 857 名健康受试者（平均年龄=56.1±9.9 岁；年龄范围 24.9-84.8 岁）。所有受试者均在 3T 上进行扫描。我们使用 TBSS 检查年龄和性别对白质中 FA、AD 和 RD 的影响。
整体 FA 与年龄呈负相关（R(2) = 0.18，P <.0001），整体 AD 和 RD 与年龄呈正相关（AD：R(2) = 0.02，P <.0001；RD：R(2) = 0.19，P <.0001）。然而，AD 与年龄的相关性较弱。体素分析显示，FA 与年龄呈负相关的区域较多，这些区域中 RD 与年龄的正相关性较强。在一些白质区域，FA 随着年龄的增长而增加。体素分析还显示，FA、AD 或 RD 在男性和女性之间存在差异的区域较多；然而，没有区域显示年龄和性别之间存在显著的交互作用。
我们的研究结果表明，与轴突退变相比，大脑白质完整性的年龄相关性变化与髓鞘退变的相关性更强，在一些特定区域，随着年龄的增长，髓鞘再形成的轴突数量可能会增加。我们的研究结果还表明，在大脑白质的老化过程中，男女之间没有性别差异。
