Alzheimer’s disease (AD) is the most prevalent dementia in the world. Its cause(s) are presently largely unknown. The most common explanation for AD, now, is the amyloid cascade hypothesis, which states that the cause of AD is senile plaque formation by the amyloid β peptide, and the formation of neurofibrillary tangles by hyperphosphorylated tau. A second, burgeoning theory by which to explain AD is based on the infection hypothesis. Much experimental and epidemiological data support the involvement of infections in the development of dementia. According to this mechanism, the infection either directly or via microbial virulence factors precedes the formation of amyloid β plaques. The amyloid β peptide, possessing antimicrobial properties, may be beneficial at an early stage of AD, but becomes detrimental with the progression of the disease, concomitantly with alterations to the innate immune system at both the peripheral and central levels. Infection results in neuroinflammation, leading to, and sustained by, systemic inflammation, causing eventual neurodegeneration, and the senescence of the immune cells. The sources of AD-involved microbes are various body microbiome communities from the gut, mouth, nose, and skin. The infection hypothesis of AD opens a vista to new therapeutic approaches, either by treating the infection itself or modulating the immune system, its senescence, or the body’s metabolism, either separately, in parallel, or in a multi-step way.

阿尔茨海默病 (AD) 是世界上最普遍的痴呆症。其原因目前在很大程度上是未知的。现在，对 AD 最常见的解释是淀粉样蛋白级联假说，该假说指出，AD 的原因是淀粉样蛋白 β 肽形成老年斑，以及过度磷酸化 tau 形成神经原纤维缠结。另一个用来解释 AD 的新兴理论是基于感染假说。许多实验和流行病学数据支持感染与痴呆症的发展有关。根据这种机制，直接或通过微生物毒力因子的感染先于淀粉样蛋白 β 斑块的形成。具有抗菌特性的淀粉样蛋白 β 肽可能在 AD 的早期阶段有益，但随着疾病的进展变得有害，伴随着外周和中枢水平的先天免疫系统的改变。感染导致神经炎症，导致全身炎症并由其持续，最终导致神经变性和免疫细胞衰老。AD 相关微生物的来源是来自肠道、口腔、鼻子和皮肤的各种身体微生物群落。AD 的感染假说为新的治疗方法开辟了前景，无论是通过治疗感染本身，还是通过单独、并行或多步骤的方式调节免疫系统、其衰老或身体的新陈代谢。以及免疫细胞的衰老。AD 相关微生物的来源是来自肠道、口腔、鼻子和皮肤的各种身体微生物群落。AD 的感染假说为新的治疗方法开辟了前景，无论是通过治疗感染本身，还是通过单独、并行或多步骤的方式调节免疫系统、其衰老或身体的新陈代谢。以及免疫细胞的衰老。AD 相关微生物的来源是来自肠道、口腔、鼻子和皮肤的各种身体微生物群落。AD 的感染假说为新的治疗方法开辟了前景，无论是通过治疗感染本身，还是通过单独、并行或多步骤的方式调节免疫系统、其衰老或身体的新陈代谢。