Despite major advances, our understanding of the neurobiology of life course socioeconomic conditions is still scarce. This study aimed to provide insight into the pathways linking socioeconomic exposures—household income, last known occupational position, and life course socioeconomic trajectories—with brain microstructure and cognitive performance in middle to late adulthood. We assessed socioeconomic conditions alongside quantitative relaxometry and diffusion-weighted magnetic resonance imaging indicators of brain tissue microstructure and cognitive performance in a sample of community-dwelling men and women (N = 751, aged 50–91 years). We adjusted the applied regression analyses and structural equation models for the linear and nonlinear effects of age, sex, education, cardiovascular risk factors, and the presence of depression, anxiety, and substance use disorders. Individuals from lower-income households showed signs of advanced brain white matter (WM) aging with greater mean diffusivity (MD), lower neurite density, lower myelination, and lower iron content. The association between household income and MD was mediated by neurite density (B = 0.084, p = 0.003) and myelination (B = 0.019, p = 0.009); MD partially mediated the association between household income and cognitive performance (B = 0.017, p < 0.05). Household income moderated the relation between WM microstructure and cognitive performance, such that greater MD, lower myelination, or lower neurite density was only associated with poorer cognitive performance among individuals from lower-income households. Individuals from higher-income households showed preserved cognitive performance even with greater MD, lower myelination, or lower neurite density. These findings provide novel mechanistic insights into the associations between socioeconomic conditions, brain anatomy, and cognitive performance in middle to late adulthood.

尽管取得了重大进展，我们对生命历程社会经济条件的神经生物学的理解仍然很少。这项研究旨在深入了解社会经济风险（家庭收入、最后已知的职业地位和生命历程的社会经济轨迹）与成年中后期的大脑微观结构和认知表现之间的联系路径。我们评估了社区居住男性和女性样本（N = 751，年龄 50-91 岁）的社会经济状况以及脑组织微观结构和认知表现的定量松弛测量和扩散加权磁共振成像指标。我们针对年龄、性别、教育、心血管危险因素以及抑郁、焦虑和物质使用障碍的存在的线性和非线性影响调整了应用回归分析和结构方程模型。来自低收入家庭的个体表现出大脑白质 (WM) 严重老化的迹象，平均扩散率 (MD) 较大、神经突密度较低、髓鞘形成较低和铁含量较低。家庭收入与 MD 之间的关联由神经突密度（B = 0.084，p = 0.003）和髓鞘形成（B = 0.019，p = 0.009）介导； MD 部分介导了家庭收入和认知表现之间的关联（B = 0.017，p < 0.05）。家庭收入调节了 WM 微观结构和认知表现之间的关系，例如，较高的 MD、较低的髓鞘形成或较低的神经突密度仅与低收入家庭个体较差的认知表现相关。来自高收入家庭的个体即使具有较高的 MD、较低的髓鞘形成或较低的神经突密度，也表现出保留的认知能力。这些发现为成年中后期的社会经济条件、大脑解剖结构和认知表现之间的关联提供了新颖的机制见解。