Although scientists around the world have made a lot of research on the etiology and pathogenesis of Alzheimer’s disease in genetics, biology, neurobiochemistry, and pathological anatomy, and have made a lot of progress, the real cause of the disease is still unclear. At the same time, a large number of studies have found that there are many factors that contribute to the pathogenesis or precipitating conditions of Alzheimer’s disease, and these factors and conditions are known as “risk factors” for the disease in medical terms. Some of the major risk factors associated with Alzheimer’s disease are as follows: 1. Age The brain cells of people gradually age and die as they grow older, but most people’s brain cells age to a certain point and then stop (physiological aging). If the degeneration of brain cells is serious and exceeds the degree of normal aging (pathological aging), it can lead to Alzheimer’s disease. According to the survey, the disease can occur as early as 50 years old, and the incidence rises gradually with the growth of age. In the age group of 60-90 years old, the incidence rate increases 1 times for every 5 years; the incidence rate of 80 years old and above is the highest, reaching 20%-30%; after 90 years old, it decreases. However, in our daily life, we also see many senior citizens who are strong, energetic, deaf and bright, living a normal life. This shows that advanced age is not a decisive factor for Alzheimer’s disease, and we should eliminate the misconception that “old people must have dementia”. Genetic factors have a wide range of effects on people and can lead to a variety of diseases and physiological abnormalities, and the effect on intelligence is no exception. The proportion of the normal population suffering from this disease is 1%. The proportion of those who have the disease in their family rises to 10%. The rate of twin homozygosity is also quite high, for example, KalImam (1997) investigated 108 cases of twins and found that the homozygosity rate of dizygotic twins with AD was 8.0% compared to 42.8% for monozygotic twins. In the same family, some people tend to have symptoms of the disease such as memory loss and mental decline at a certain age or even at an early age, which is known as familial early-onset AD. The genes associated with this disease are the amyloid precursor protein (APP) gene located on chromosome 21, the progerin-1 (PS-1) gene located on chromosome 12, and the gene located on chromosome 1. 1) gene on chromosome 12 and progerin-2 (PS-2) gene on chromosome 1. The frequency of E4 (ε4) in the APOE genotype is significantly higher in AD patients, and the survival period of AD patients with ε4 gene is shorter than that of AD patients without this gene. 3. Cerebrovascular lesions Elderly people are prone to hypertension, diabetes, hyperlipidemia, heart disease and other diseases, which are all risk factors for cerebrovascular lesions and can lead to cerebral arteriosclerosis, cerebral infarction, cerebral hemorrhage and other cerebrovascular lesions. Cerebrovascular lesions can reduce cerebral blood flow and oxygen supply, decrease cell metabolism, and eventually lead to the death of nerve cells, resulting in a decrease in the number of cells and dementia. Currently, it is believed that vascular lesions are one of the important factors of “apoptosis” (cell suicide caused by activation of intracellular death program), so cerebrovascular lesions are not only the fundamental factor leading to cerebrovascular dementia (VD), but also a risk factor for AD. Therefore, adopting a good lifestyle, controlling blood sugar, lipids and blood pressure, and preventing cerebrovascular lesions are effective measures to avoid mental decline in old age. Neurotransmitters Neurotransmitters are a class of substances that transmit information between nerve cells and play an important role in maintaining the normal function of the nervous system. There are many kinds of neurotransmitters in human body, and a large number of studies have proved that Alzheimer’s disease is accompanied by a variety of neurotransmitter disorders in the brain, and the main neurotransmitter disorders considered to be related to this disease are acetylcholine (ACh), monoamines, amino acids and neuropeptides, among which the reduction of ACh is the most prominent. The cholinergic neurons that produce ACh in the brain of dementia patients are significantly reduced, and ACh is related to people’s learning and memory ability, and the reduction of Ach directly leads to the impairment of intelligence. A large number of clinical trials have proved that using drugs to increase the concentration of acetylcholine in the brain can lead to a significant improvement in memory in this disease. Thus, the most effective drugs for the treatment of Alzheimer’s disease are currently cholinesterase inhibitors that increase the concentration of acetylcholine in the brain. The purpose of inhibiting this enzyme is to reduce the breakdown of ACh and increase the concentration of ACh in the brain, thus achieving a therapeutic effect, which supports the correlation between ACh and Alzheimer’s disease from one side. In addition, monoamine neurotransmitters such as norepinephrine, 5-hydroxytryptamine, and dopamine were significantly reduced in the brain of Alzheimer’s patients; amino acid neurotransmitters such as glutamate and gamma-aminobutyric acid were significantly reduced; neuropeptides such as growth hormone, adrenocorticotropin-releasing hormone, substance P, neuropeptide, opioid peptide, and arginine The neuropeptides such as growth hormone, adrenocorticotropin-releasing hormone, substance P, neuropeptide, opioid peptide and arginine were also significantly reduced. The reduction of many neurotransmitters in the brain will not only widely affect the patient’s intelligence and mental activities, but also lead to the death of nerve cells and promote the occurrence of senile dementia. 5, literacy It is believed that early education directly increases the number, reserve and expansion capacity of brain cells, and the lack of literacy can cause a slow and lasting lack of intellectual stimulation. After retirement, some elderly people feel that they are “old” and are usually too lazy to use their brains, resulting in long-term brain inhibition, lack of stimulation of brain cells, brain functions are not used and strengthened, resulting in gradual aging and decay of the brain, which can easily lead to senile dementia. Domestic survey data show that the lower the level of education, the higher the incidence of the disease, the illiterate group incidence rate (2.2%) is much higher than the elementary school group (0.84%) and secondary school group (0.81%). This suggests that the level of education is closely related to the incidence of the disease. Some surveys also found that people with high IQ and large brain volume have a low incidence of the disease due to adequate brain cell reserves. Therefore, after retirement, moderate brain activity, participate in social activities, is conducive to the prevention of this disease. 6, dietary habits How smoking is related to Alzheimer’s disease has gone through a long process of recognition. Initially, it was thought that the number of nicotinic receptors in the cerebral cortex of Alzheimer’s patients was reduced, and the nicotine component of cigarettes could increase the number of this receptor in the brain, and it was assumed that smoking could prevent and treat Alzheimer’s disease. Some researchers have reached the erroneous conclusion that smoking prevents the disease through a small number of incomplete clinical trials. Recent investigations with larger samples have confirmed that the incidence of the disease is 2-3 times higher in smokers compared to nonsmokers, and that vascular dementia is more common. Therefore, smoking is not only unable to prevent and treat Alzheimer’s disease, but also promotes other physical diseases (such as chronic bronchitis, emphysema, lung cancer, etc.) that can contribute to the development of this disease. In addition, alcohol is a narcotic and a pro-neurotic substance. A large amount of alcohol consumption at one time can lead to acute intoxication and manifest as mental confusion. Long-term heavy drinking can produce alcohol dependence and chronic alcoholism, causing premature degeneration and death of brain cells, and eventually irreversible dementia – alcoholic dementia. Some investigations have found that long-term consumption of small amounts of red wine can reduce the occurrence of this disease, but this result is not related to alcohol itself, but to the antioxidant effect of red wine. It is now believed that free radicals are related to the occurrence of Alzheimer’s disease. During the oxidative metabolism of human brain cells, a substance called “free radicals” is produced, which collects in the cells and can damage cell membranes, leading to cell death and aging of the organism. Because of the high utilization of oxygen by brain cells , more vulnerable to free radical attack. Antioxidants can reduce the production of free radicals, thus reducing the occurrence of Alzheimer’s disease. Usually more in antioxidant-rich foods, such as vitamin C, vitamin E and beta carrots, are beneficial to anti-aging and prevention of this disease. Drug clinical trials have confirmed that vitamin E has a therapeutic effect on patients with mild cases of the disease. In the food we usually eat, various vegetable oils are rich in vitamin E; fresh vegetables and fruits are the main source of vitamin C. Oranges, sour dates and hawthorn contain more vitamin C; beta carotene is mainly from carrots. 7, traumatic brain injury Current research has confirmed that the brain tissue of patients after traumatic brain injury has age spots, neurofibrillary tangles and other neuropathological tissue changes similar to Alzheimer’s disease. Therefore, traumatic brain injury is related to the occurrence of this disease. Severe traumatic brain injury can cause severe damage to brain tissue, resulting in hemorrhage, edema and necrosis, predisposing to traumatic dementia. Boxers with long-term frequent mild traumatic brain injury can develop chronic progressive dementia, called boxer’s dementia. Patients with definite head trauma have a greatly increased risk of developing Alzheimer’s disease. For example, carriers of the APOE4 gene are at greater risk of developing Alzheimer’s disease once they have suffered a head trauma. Pathological anatomy reveals that neurofibrillary tangles, which are characteristic of Alzheimer’s disease, are most common in the brain tissue of people with traumatic brain injury. Therefore, avoiding traumatic brain injury is beneficial in preventing Alzheimer’s disease. 8, aluminum element Aluminum may be related to the occurrence of Alzheimer’s disease, in 1973, someone first found that the content of aluminum in the brain tissue of patients with Alzheimer’s disease is 10 to 30 times higher than normal people (1 gram of brain tissue contains 1.9 micrograms of aluminum in normal people). In animal tests, when soluble aluminum salts were injected into the brains of rabbits, the brain tissue produced neurofibrillary changes characteristic of Alzheimer’s disease – neurofibrillary tangles. Long-term inhalation of air rich in aluminum oxide dust can lead to serious intellectual damage, with a 4.5-fold increase in the risk of intellectual damage in people who have been inhaling for more than 20 years, a 3.1-fold increase in people who have been inhaling for 10 to 20 years, and a 2.4-fold increase in people who have been inhaling for 1 to 10 years. However, some people believe that aluminum has little to do with Alzheimer’s disease, and they found that aluminum concentrations in the brains of people on long-term dialysis for renal failure did not cause dementia in patients despite high levels. Although the relationship between aluminum and Alzheimer’s disease is still controversial, we still recommend that the consumption of food and drinking water containing high amounts of aluminum be strictly limited and avoided. 9, psychosocial factors Currently, more and more attention is being paid to the relationship between psychosocial factors and Alzheimer’s disease. It has been found that more than 20 kinds of psychosocial factors are related to the development of this disease, most of which belong to the so-called negative life events that are unfavorable to the mental and physical health of the elderly, such as tension, anxiety, depression, and less activity. These life events are a kind of stress to the human body, causing the dysfunction of the nervous and endocrine systems in the body, causing a large secretion of adrenocorticotropic hormones, leading to emotional tension, anxiety and changes in vascular constriction, predisposing to cardiovascular disease and other somatic diseases, and contributing to the occurrence of Alzheimer’s disease. Therefore, in daily life, one should maintain a happy mood, participate in appropriate cultural activities and avoid negative life events, which can help prevent the occurrence of this disease. 10. Many studies have found that the incidence rate of Alzheimer’s disease is higher in women than in men, 1.5 to 3.0 times that of men. The higher incidence in women than men has prompted an exploration of the relationship between estrogen and Alzheimer’s disease. Studies have found that female Alzheimer’s patients have lower levels than normal elderly women compared to the former, who have a 67% lower risk of developing the disease , and that taking estrogen improves the intelligence of women with Alzheimer’s disease. Some basic research has also found that reduced estrogen levels may have a direct adverse effect on the function and growth of nerve cells. However, this is only a theoretical discussion and has yet to be proven in clinical trials. Moreover, because long-term estrogen use increases the risk of endometrial cancer, doctors are not yet advocating estrogen treatment for Alzheimer’s disease. In addition, a series of studies have found that people with occupational exposure to electromagnetic fields have an increased risk of developing Alzheimer’s disease. EMFs may induce certain biological processes associated with pathological changes in Alzheimer’s disease, affecting neurons and causing nerve cell lesions. Cell phones are located close to the temporal side of the brain and emit high-frequency electromagnetic waves when talking, so it is not clear whether they are susceptible to Alzheimer’s disease in the long term. It has been suggested that people who are exposed to vibration for long periods of time are also susceptible to Alzheimer’s disease, such as those who drive trucks, operate wind drills, chain saws or other vibrating tools, but the findings of many studies are inconsistent. Therefore, this is only a theoretical discussion, and there is absolutely no need for us to be nervous and fearful about it.