Valdés Hernández M, Allerhand M, Glatz A, Clayson L, Muñoz Maniega S, Gow A, Royle N, Bastin M, Starr J, Deary I, Wardlaw J
Department of Neuroimaging Sciences, Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK.
Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK.
Eur J Neurol. 2016 Jul;23(7):1202-9. doi: 10.1111/ene.13006. Epub 2016 Apr 20.
Several studies have reported associations between brain iron deposits (IDs), white matter hyperintensities (WMHs) and cognitive ability in older individuals. Whether the association between brain IDs and cognitive abilities in older people is mediated by or independent of total brain tissue damage represented by WMHs visible on structural magnetic resonance imaging (MRI) was examined.
Data from 676 community-dwelling individuals from the Lothian Birth Cohort 1936, with Mini-Mental State Examination scores >24, who underwent detailed cognitive testing and multimodal brain MRI at mean age 72.7 years were analysed. Brain IDs were assessed automatically following manual editing. WMHs were assessed semi-automatically. Brain microbleeds were visually counted. Structural equation modelling was used to test for mediation.
Overall, 72.8% of the sample had IDs with a median total volume of 0.040 ml (i.e. 0.004% of the total brain volume). The total volume of IDs, significantly and negatively associated with general cognitive function (standardized β = -0.17, P < 0.01), was significantly and positively associated with WMH volume (std β = 0.13, P = 0.03). WMH volume had a significant negative association with general cognitive function, independent of IDs (std β = -0.13, P < 0.01). The association between cognition and IDs in the brain stem (and minimally the total brain iron load) was partially and significantly mediated by WMH volume (P = 0.03).
The negative association between brain IDs and cognitive ability in the elderly is partially mediated by WMHs, with this mediation mainly arising from the iron deposition load in the brain stem. IDs might be an indicator of small vessel disease that predisposes to white matter damage, affecting the neuronal networks underlying higher cognitive functioning.
多项研究报告了老年个体脑铁沉积（ID）、白质高信号（WMH）与认知能力之间的关联。本研究旨在探讨老年人脑ID与认知能力之间的关联是由结构磁共振成像（MRI）上可见的WMH所代表的全脑组织损伤介导的，还是与之无关。
对来自洛锡安出生队列1936的676名社区居住个体的数据进行分析，这些个体的简易精神状态检查得分>24，平均年龄72.7岁时接受了详细的认知测试和多模态脑MRI检查。脑ID在手动编辑后自动评估。WMH采用半自动评估。脑微出血通过视觉计数。采用结构方程模型进行中介检验。
总体而言，72.8%的样本有ID，总中位数体积为0.040 ml（即占全脑体积的0.004%）。ID的总体积与一般认知功能显著负相关（标准化β=-0.17，P<0.01），与WMH体积显著正相关（标准化β=0.13，P=0.03）。WMH体积与一般认知功能显著负相关，独立于ID（标准化β=-0.13，P<0.01）。脑干中认知与ID之间的关联（以及至少全脑铁负荷）部分且显著地由WMH体积介导（P=0.03）。
老年人脑ID与认知能力之间的负相关部分由WMH介导，这种中介作用主要源于脑干中的铁沉积负荷。ID可能是小血管疾病的一个指标，易导致白质损伤，影响高级认知功能的神经元网络。
