Behavioral and motor infantilism is a clinical manifestation of Alzheimer’s disease dementia. What are the reasons for the development of childish and stupid behavior: 1. Education level There are more and more reports that low education level is related to the increased prevalence of dementia. In Shanghai, the prevalence of dementia and AD was reported to be 6.9% for illiterates and 1.2% for those with more than 6 years of schooling. A recent Italian epidemiological survey had similar findings. However, a Japanese case-control study did not find an association between education level and dementia and/or dementia subtypes. There is no reasonable explanation for this, and some scholars believe it is due to systematic error. Since most epidemiological studies have used a two-stage screening examination method in which patients with a positive screening test are then diagnostically examined, illiterate or poorly educated individuals may have low scores on cognitive tests at the screening stage and may easily enter the diagnostic examination stage and be diagnosed with dementia, making the prevalence higher, when in fact these individuals may not have cognitive decline at all. The idea that this is due to the biological characteristics of illiteracy itself, rather than an educational problem, and that education is related to socioeconomic status, further complicates the issue. However, Zhang Mingyuan et al. (1990) avoided this systematic error by using different screening cut-off values depending on the literacy level of the screened subjects, with the result that the prevalence of dementia remained higher in those with low levels of education. This result has since been confirmed by several studies. The etiological link between low education and AD is still not well understood, and a possible explanation is that early educational training promotes the development of cortical synapses, resulting in an increase in the number of synapses and an increase in “brain reserve”, thus delaying the diagnosis of dementia. This hypothesis is supported by clinical observations, for example, that patients with AD with high levels of education retain some cognitive function even in advanced stages, and that they have a relatively short disease course from diagnosis to death. Low education level has a similar relationship with vascular dementia and other secondary dementias. 2. Head trauma Head trauma refers to head trauma with impaired consciousness, and traumatic brain injury has been reported more frequently as a risk factor for AD. 12 case-control studies, 3 found a significant association; 4 had more history of previous trauma in AD than controls, but were not statistically significant, and the remaining 5 did not find any association between the two. However, more interest was recently reported in a follow-up study of severe traumatic brain injury, in which Robert et al. followed patients with severe traumatic brain injury for an average of 25 years and found AD-like β-amyloid deposits in the brain tissue of about 1/3 of the patients. Clinical and epidemiological studies suggest that severe traumatic brain injury may be an etiology of some AD. As far as the present data are concerned, head trauma may be a risk factor for AD, but it is not certain. 3. High or low maternal childbearing age (>40 years or <20 years) may be a risk factor for AD due to Down's syndrome (DS), and the risk of DS increases with maternal childbearing age. There are 9 case-control studies, some finding an association, some finding a difference but not statistically significant, or not finding an association at all, and some considering only some risk factors for disseminated AD.