Alzheimer’s disease is the most common neurodegenerative disease in the elderly and is one of the major diseases affecting the quality of life of middle-aged and older adults. Knowledge of the natural course, risk factors and pathophysiology of Alzheimer’s disease provides great help in preventing and delaying the development of the disease, and knowledge of the natural course can help in choosing the appropriate time of intervention.The natural course of AD can be roughly divided into four phases, which are the normal phase (no AD brain pathology changes), pre-AD symptoms (early brain changes), mild cognitive impairment ( aggravation of AD brain changes) and clinical AD (typical AD brain changes). Primary prevention refers to measures (including medications, changes in lifestyle habits) for healthy or at-risk populations. In the case of AD, there is no strict distinction between primary and secondary preventive measures.In AD, the biological changes have been present for many years, possibly decades, before the onset of symptoms. This means that primary prevention measures for those at high risk are equally applicable to those whose brains are already showing early AD changes. Secondary prevention is used for people in the very early clinical stages of AD who may not meet the clinical diagnostic criteria for AD and who are currently categorized as having mild cognitive impairment (MCI). This concept tends to include and categorize people with cognitive problems who can barely be considered “normal” and who clearly do not meet the criteria for “dementia. Most people with MCI complain of poor memory when confronted by a doctor and can be categorized as having “amnestic MCI”. There is a large overlap between primary prevention for asymptomatic high-risk groups and secondary prevention for people with MCI. Risk factors for AD include increasing age [1], genetic factors (especially early-onset dementia) [2], low educational level [3], increased systolic blood pressure in middle age [4], hypercholesterolemia [5], and diabetes mellitus, and possible risk factors include smoking [6], alcohol consumption [7], and head trauma [8]. Genetic factors play an important role in determining an individual’s susceptibility to become AD susceptible, with individuals with a family history of AD at any age being four times more likely to develop AD than normal individuals. As with genetic factors, gender, increasing age and low education levels are non-interventionist risk factors. In recent years, primary prevention of AD has only been on the agenda as intervenable vascular risk factors such as hypertension, hypercholesterolemia, diabetes mellitus, and cigarette smoking have gradually been proposed. Health education as an important intervention for primary prevention should be emphasized. 1.1 Hypertension Hypertension is associated with cognitive impairment, cerebral white matter damage, hippocampal atrophy, clinical dementia, and AD neuropathology occurring in later life.Data from a study by Miia Kivipelto et al. demonstrated that the risk of AD in later life was significantly higher in individuals with systolic hypertension in midlife than in those who were normotensive (OR 2.3, 95% CI 1.0-5.5), and the study did not confirm a relationship between diastolic blood pressure and the relationship between diastolic blood pressure and the development of AD in later life [4]. Some clinical studies have reported a reduced risk of AD in individuals using antihypertensive drugs. In the Kungsholmen study diuretic use was found to reduce the risk of AD in older adults over 75 years of age [9]. However, there are a number of contrary findings reporting that antihypertensive treatment does not or only mildly improves cognitive function or dementia. Hypertensive disease is a risk factor for a variety of diseases, not only increasing the risk of dementia in the elderly population, but also being a major risk factor for coronary heart disease and stroke. The first physician should ask for blood pressure measurements for all patients, recommend a review for those found to be above the normal high limit for the first time to clarify the diagnosis, and either verbally supervise them or distribute relevant hypertension prevention and treatment brochures to enhance self-care awareness in the elderly high-risk group. According to the data of hypertension prevention and treatment research, the self-awareness rate, the rate of reasonable medication taking, and the rate of blood pressure control of Chinese residents suffering from hypertension are at a relatively low level. Only by improving the awareness of hypertension prevention and treatment in the middle-aged population can we fundamentally achieve the primary prevention of AD. Reduce the incidence of AD in the elderly population. 1.2 Diabetes mellitus Epidemiologic studies have shown that diabetic patients have a two- to three-fold increase in the risk of AD compared with individuals with normal blood glucose, and that diabetes mellitus is a high-risk factor for AD, especially in those with AD combined with cerebrovascular disease. This is a fairly positive result because this study was based on ethnically diverse groups with different lifestyles, including Japanese, American, European Caucasian, and religious populations.Luchsinger followed 1,262 people who were free of dementia at baseline for an average of 4.3 years, and after analysis of Cox’s ratio risk regression modeling, the results showed that people with diabetes were more likely to develop AD-type dementia ( RR1.3, 95% CI0.8-1.9) [10]. Diabetes mellitus, especially type 2 diabetes mellitus, is highly prevalent in middle-aged and elderly patients. Whether it is type 1 or type 2 diabetes, rational diet is a prerequisite for all treatments, in addition, postprandial exercise is a fundamental treatment. Some patients can keep their blood glucose in a good range by eating well and exercising, avoiding or slowing down the intervention of medications and avoiding their adverse effects. Hypoglycemia with oral medications or insulin therapy can cause damage to the central nervous system. Self-monitoring of blood glucose is important for people with diabetes, not only to detect hypoglycemia in time for effective treatment, but also to recognize the relationship between diet and blood glucose, thus improving compliance with treatment. 1.3 Hypercholesterolemia Several studies have looked at the relationship between cholesterol levels and AD in midlife.Miia Kivipelto studied both hypertension and hypercholesterolemia over a 5-year follow-up period.High cholesterol levels (6.5 mmol/l) increased the risk of developing AD (OR 2.1, 95% CI 1.0-4.4)[11].Evans’ study also confirmed that elevated total cholesterol levels increase the risk of AD, but only in those without APOEε4, and not in those with high cholesterol with APOEε4 [12]. It is difficult to explain such results, but in the present study, the APOEε4 allele has been widely accepted as an important predictor of AD. Hypercholesterolemia is strongly associated with poor dietary habits, and a low-fat diet and exercise are the best ways to prevent hypercholesterolemia. It is important that individuals with ineffective dietary and exercise control take lipid-lowering drugs in appropriate conjunction, but adequate attention should be paid to the hepatic adverse effects of lipid-lowering drugs. 1.4 Smoking and Alcohol Consumption The pathophysiological effects of smoking on the body are multifaceted and promote neuropathic and vascular diseases through several pathways: increased risk of coronary heart disease (CHD) and cerebrovascular disease (CVD), increased risk of oxidative stress, and activation of macrophages leading to more oxidative damage. The relationship between smoking and AD is controversial, with early data from case-control studies suggesting that smoking reduces the risk of AD, however, more recent prospective studies in homozygous individuals have repeatedly suggested that smoking increases the risk of AD [6,13], particularly in individuals without the apoE ε4 allele, and there is evidence of an unbalanced pre-mortem mortality in middle-aged smokers carrying the ε4 allele, but again there are studies that have not demonstrated a correlation between smoking and AD [14]. The relationship between alcohol consumption and the risk of AD is uncertain, but the relationship between excessive alcohol consumption and cardiovascular disease is certain, so “stopping smoking and limiting alcohol consumption” is positively desirable for the prevention of AD. 1.5 Lifestyle The prevention of AD is the most critical. For patients who have developed clinical AD, treatment is limited, and most of them require long-term medication, the efficacy of which is highly uncertain. Cultivating a good lifestyle at an early age will last a lifetime. The main ones are proper diet and physical activity. Diet can indirectly affect the development of AD, e.g. high cholesterol intake increases the risk of hypercholesterolemia and high salt intake increases the risk of hypertension. Common food antioxidants include carotenoids (β-carotene), ascorbic acid (VitC), tocopherols (VitE) and flavonoids. Consumption of foods containing these antioxidants can counteract the damage caused by oxidative stress. Physical activity (PA) increases brain neuromodulators, especially brain-derived neurotrophic factors. Several studies have been published on the relationship between PA and dementia risk. Some studies have shown that those individuals who participate in more physical activity will have a reduced incidence of dementia [15]. There is growing evidence that both physical and leisure activities and brain-stimulating activities can attenuate cognitive decline and reduce the risk of AD [16,17]. However, some studies have also shown a reduction in the incidence of dementia only in certain subsamples, such as those carrying the apoEε4 allele. Although it has been reported that physical activity does not have an effect on the development of dementia, increasing physical activity is a safe recommendation for people with AD, and exercise can produce many other benefits.