The global population is aging, leading to an increasing burden of age-related neurodegenerative disease. Efforts to intervene against age-related dementias in older adults have generally proven ineffective. These failures suggest that a lifetime of brain aging may be difficult to reverse once widespread deterioration has occurred. To test interventions in younger populations, biomarkers of brain aging are needed that index subtle signs of accelerated brain deterioration that are part of the putative pathway to dementia. Here I review potential MRI-based biomarkers that could connect midlife brain aging to later life dementia. I survey the literature with three questions in mind, 1) Does the biomarker index age-related changes across the lifespan? 2) Does the biomarker index cognitive ability and cognitive decline? 3) Is the biomarker sensitive to known risk factors for dementia? I find that while there is preliminary support for some midlife MRI-based biomarkers for accelerated aging, the longitudinal research that would best answer these questions is still in its infancy and needs to be further developed. I conclude with suggestions for future research.

全球人口正在老龄化，导致与年龄有关的神经退行性疾病的负担增加。事实证明，干预老年人与年龄有关的痴呆症的努力无效。这些失败表明，一旦发生广泛的恶化，大脑衰老的一生可能很难逆转。为了测试对年轻人群的干预措施，需要大脑衰老的生物标志物，以索引加速的大脑退化的细微迹象，这些迹象是假定的痴呆症途径的一部分。在这里，我回顾了潜在的基于MRI的生物标记物，它们可以将中年大脑衰老与晚年痴呆症联系起来。我在调查文献时会想到三个问题，1）生物标志物指数在整个生命周期中是否与年龄相关？2）生物标志物是否能识别认知能力和认知能力？3）生物标志物是否对痴呆的已知危险因素敏感？我发现，尽管对于加速衰老的中年基于MRI的生物标记物已经有了初步的支持，但能够最好地回答这些问题的纵向研究仍处于起步阶段，需要进一步发展。最后，我提出了对未来研究的建议。