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

中文翻译：

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成年中后期白质束的微观结构差异：一项对 7167 名英国生物银行参与者的扩散 MRI 研究

白质纤维束显示出对衰老影响的异质脆弱性。在这里，我们使用 UK Biobank 扩散磁共振成像数据估计了 7167 名 47 至 76 岁的神经系统健康人（3368 名男性和 3799 名女性）与年龄相关的管道特性差异。在 76 个纤维束上采样了在广义分数各向异性、轴向扩散率、径向扩散率和平均扩散率方面的束特性；对于每个区域，通过在线性模型中将这些指数与年龄进行拟合来估计与年龄相关的差异。这项横断面研究展示了 4 种年龄差异模式。占主导地位的模式是较低的广义各向异性分数和较高的轴向扩散率、径向扩散率和随年龄增长的平均扩散率，构成 76 个区域中的 45 个，主要涉及关联、投影、和连接前额叶的连合纤维。其他 3 种模式仅构成 14 束，扩散指数的年龄差异不典型，主要涉及顶叶、枕叶和颞叶皮质。通过分析英国生物银行提供的大量弥散磁共振成像数据，该研究详细描述了整个大脑中与年龄相关的异质性差异，这通常支持骨髓变性假说。