■晚期重度抑郁症(MDD)是轻度认知障碍(MCI)和阿尔茨海默病的危险因素。然而,对灰质变化的研究得出了不同的估计,即哪些结构与MDD和痴呆有关。灰质体积和皮质厚度的变化是自由水积聚和树突状脊柱损失的微观结构过程的宏观结构量度。
■我们进行了多壳扩散成像,以评估244名缓解MDD的老年人(n=44)的灰质微结构,MCI(n=115),汇出的MDD+MCI(n=61),或无精神障碍或认知障碍(健康对照参与者;n=24)。我们估计了与神经突密度有关的测量值,取向色散,和自由水(各向同性体积分数)使用生物物理上合理的模型(神经突取向分散和密度成像)。
■结果表明,年龄的增加与各向同性体积分数的增加和取向分散指数的降低有关,这与神经病理学树突丢失一致。此外,MCI组比缓解MDD组或健康对照组更容易破坏年龄和各向同性体积分数增加之间的这种关系.然而,所有3组的年龄和取向离散度指数之间的关联相似.
■研究结果表明,神经突方向分散和密度成像措施可用于识别阿尔茨海默病的生物学风险因素,表明MCI观察到的常规神经变性和MDD中观察到的树突丢失。
UNASSIGNED: Major depressive disorder (MDD) in late life is a risk factor for mild cognitive impairment (MCI) and Alzheimer\'s disease. However, studies of gray matter changes have produced varied estimates of which structures are implicated in MDD and dementia. Changes in gray matter volume and cortical thickness are macrostructural measures for the microstructural processes of free water accumulation and dendritic spine loss.
UNASSIGNED: We conducted multishell diffusion imaging to assess gray matter microstructure in 244 older adults with remitted MDD (n = 44), MCI (n = 115), remitted MDD+MCI (n = 61), or without psychiatric disorders or cognitive impairment (healthy control participants; n = 24). We estimated measures related to neurite density, orientation dispersion, and free water (isotropic volume fraction) using a biophysically plausible model (neurite orientation dispersion and density imaging).
UNASSIGNED: Results showed that increasing age was correlated with an increase in isotropic volume fraction and a decrease in orientation dispersion index, which is consistent with neuropathology dendritic loss. In addition, this relationship between age and increased isotropic volume fraction was more disrupted in the MCI group than in the remitted MDD or healthy control groups. However, the association between age and orientation dispersion index was similar for all 3 groups.
UNASSIGNED: The findings suggest that the neurite orientation dispersion and density imaging measures could be used to identify biological risk factors for Alzheimer\'s disease, signifying both conventional neurodegeneration observed with MCI and dendritic loss seen in MDD.