Cross-sectional white matter microstructure differences in age and trait mindfulness

The process of aging can be characterized by a decline in cognitive performance, which may be accompanied by deterioration in specific structural properties of the brain. In this study we sought to investigate to what extent mindfulness changes over the aging process, and which alterations in brain structure can be associated to aging and concomitant changes in mindfulness. We collected Mindful Attention Awareness Scale questionnaire data to assess trait mindfulness and acquired diffusion-weighted imaging data fitted to the diffusion tensor model (DTI) in a group of 97 middle-aged to elderly participants. Our results showed that trait mindfulness increased with age. In terms of white matter structure our results suggested that there was a general increase of omnidirectional diffusion, which favored radial over axial diffusivity, leading to a decrease in fractional anisotropy (FA) in older participants. We further showed that trait mindfulness mediated the FA-age effect in a localized area consisting of the internal and external capsule, as well as the corona radiata. The implication of this mediation analysis is that trait mindfulness may deter age-associated neurocognitive decline, perhaps by preventing age-associated microlesions specifically in cortico-subcortical white matter tracts. This study can be considered a pioneer of using DTI studies to investigate the relationship between age and trait mindfulness.衰老进程的典型特征为认知能力下降，常伴随大脑特定结构属性的退行性改变。本研究旨在探究衰老过程中正念（mindfulness）水平的变化幅度，以及哪些大脑结构改变与衰老及正念水平的伴随变化存在关联。本研究招募97名中老年参与者，收集了用于评估特质正念的正念注意觉知量表（Mindful Attention Awareness Scale）问卷数据，以及拟合了扩散张量模型（diffusion tensor model, DTI）的扩散加权成像数据。研究结果显示，特质正念水平随年龄增长而提升。针对大脑白质结构的分析表明，老年群体的全向扩散整体增强，且径向扩散相较于轴向扩散更具优势，最终导致各向异性分数（fractional anisotropy, FA）降低。进一步分析发现，在内囊、外囊及辐射冠组成的局部脑区内，特质正念对年龄与FA的关联存在中介效应。该中介分析的启示在于，特质正念或可延缓与衰老相关的神经认知衰退，其潜在机制可能是通过特异性阻断皮层-皮层下白质束中与衰老相关的微损伤形成。本研究可视为利用扩散张量成像（DTI）探究年龄与特质正念之间关联的开创性研究。