Alzheimer's disease may be a group of heterogeneous diseases, which is caused by a variety of factors (including biological and psychosocial factors). From the current research, there are more than 30 possible factors and hypotheses, such as family history, female, head injury, low education level, thyroid disease, too high or too low childbearing age, virus infection and so on. The following factors are related to the onset of the disease
1. Family history
Most epidemiological studies suggest that family history is a risk factor for the disease. The family members of some patients with the same disease were higher than the general population. In addition, the risk of congenital stupidity was increased. Further genetic studies confirmed that the disease may be caused by autosomal dominant genes. Recently, through gene mapping, we found that the pathological gene of amyloid protein in brain is located on chromosome 21. It is certain that dementia is related to heredity.
Congenital stupidity (DS) has similar pathological changes. If DS lives to adults, the probability of the disease is about 100%. It is known that the pathogenic gene of DS is located on chromosome 21, which has aroused great interest in the genetic research of the disease. However, it is difficult to study the genetics of the disease. Most researchers found that the risk rate of family members of patients with the disease is about 3-4 times higher than that of the general population. St. George Hyslop et al. (1989) reviewed the family data of the disease and found that the risk of the disease was 14.4% for parents; 8% - 13.9% of siblings. According to the statistical analysis of life span, the risk rate of fad in first-degree relatives was as high as 50%, while that in the control group was only 10%; There is only one female family in the literature, which can exclude X-linked inheritance because of its rarity. Most sporadic cases may be the result of the interaction of genetic susceptibility and environmental factors.
There are at least four known genetic sites related to AD: early onset AD loci are located on chromosome 2L, 14 and 1, respectively. The corresponding pathogenic genes were app, S182 and stm-2. The locus of late-onset AD is located on chromosome 19, and apolipoprotein E (ApoE) may be the pathogenic gene.
2. Some physical diseases
Such as thyroid diseases, immune system diseases, epilepsy, etc., have been used as the risk factors of the disease. The relative risk of hypothyroidism is high. There is a history of epilepsy before the onset of the disease. A history of migraine or severe headache was not associated with the disease. Many studies have found that the history of depression, especially the history of senile depression, is a risk factor for the disease. A recent case-control study found that in addition to depression, other functional mental disorders such as schizophrenia and paranoid psychosis are also related. Heavy metal salts, organic solvents, pesticides and drugs have been used as risk factors for the disease. The role of aluminum has always been concerned, because animal experiments show that aluminum salt has an effect on learning and memory; Epidemiological studies suggest that the prevalence of dementia is related to the content of aluminum in drinking water. The accumulation of neurotoxins such as aluminum or silicon in the body may accelerate the aging process.
3. Head injury
Head injury refers to the head injury with disturbance of consciousness. Clinical and epidemiological studies suggest that severe brain injury may be one of the causes of some of the diseases.
Progressive failure of the immune system, weakened detoxification and lentivirus infection, as well as widowhood, living alone, economic difficulties, life turbulence and other social and psychological factors can become the predisposing factors.