Alzheimer's disease (AD) is the most common cause of dementia, affecting over 25 million people globally, with 5 million new cases each year. It is strongly associated with aging, and its prevalence is expected to double every 20 years. The global prevalence of dementia in people aged 60+ years is 3.9%, with regional variations. In developed countries, about 1 in 10 older people (65+) has dementia, while over one-third of those over 85 have dementia-related symptoms. AD accounts for 50-70% of all dementia cases, with vascular dementia making up 15-25%. Prevalence rates in developing countries are generally lower than in developed nations, though some studies show similar rates to Western countries. The incidence of AD increases with age, peaking around 85 years. However, whether incidence continues to rise at advanced ages is uncertain. Women have a higher incidence of AD than men, especially among the oldest-old. Geographic variations in incidence exist, with higher rates in north-western Europe compared to southern countries. AD is associated with increased risk of death, and survival time for AD patients ranges from 3 to 6 years. Risk factors include age, gender, race, education, comorbidities, and vascular risk factors such as high blood pressure, obesity, and diabetes. Protective factors include physical activity, social engagement, and mental stimulation. Genetic factors, such as the APOE ε4 allele, are significant risk factors for AD, with increasing number of alleles increasing risk. Vascular risk factors, including high blood pressure, obesity, and diabetes, are also associated with increased risk of dementia. Smoking has been linked to increased risk of AD, while moderate alcohol consumption may have protective effects. Obesity in midlife is a risk factor for AD, while low BMI in late life may indicate preclinical AD. Dietary factors, such as high intake of saturated fats and cholesterol, increase AD risk, while diets rich in antioxidants and polyunsaturated fatty acids may be protective. Diabetes is associated with increased risk of dementia and AD, as is metabolic syndrome. Cerebrovascular disease, including stroke and white matter lesions, is also linked to dementia and AD. Psychosocial factors, such as low education, social isolation, and poor social engagement, increase dementia risk. Physical activity and mental stimulation are protective against dementia. Interventions targeting vascular risk factors, such as blood pressure control, and lifestyle factors, including physical activity and mental stimulation, may reduce dementia risk. Primary prevention strategies include managing vascular risk factors, maintaining social engagement, and promoting mental stimulation. Secondary prevention involves early detection and intervention, such as using biomarkers to identify preclinical AD. Multidomain interventions, including lifestyle changes and medical management, are being tested to delay dementia onset. Despite some promising findings, most primary prevention trials have not shown significant efficacy, highlightingAlzheimer's disease (AD) is the most common cause of dementia, affecting over 25 million people globally, with 5 million new cases each year. It is strongly associated with aging, and its prevalence is expected to double every 20 years. The global prevalence of dementia in people aged 60+ years is 3.9%, with regional variations. In developed countries, about 1 in 10 older people (65+) has dementia, while over one-third of those over 85 have dementia-related symptoms. AD accounts for 50-70% of all dementia cases, with vascular dementia making up 15-25%. Prevalence rates in developing countries are generally lower than in developed nations, though some studies show similar rates to Western countries. The incidence of AD increases with age, peaking around 85 years. However, whether incidence continues to rise at advanced ages is uncertain. Women have a higher incidence of AD than men, especially among the oldest-old. Geographic variations in incidence exist, with higher rates in north-western Europe compared to southern countries. AD is associated with increased risk of death, and survival time for AD patients ranges from 3 to 6 years. Risk factors include age, gender, race, education, comorbidities, and vascular risk factors such as high blood pressure, obesity, and diabetes. Protective factors include physical activity, social engagement, and mental stimulation. Genetic factors, such as the APOE ε4 allele, are significant risk factors for AD, with increasing number of alleles increasing risk. Vascular risk factors, including high blood pressure, obesity, and diabetes, are also associated with increased risk of dementia. Smoking has been linked to increased risk of AD, while moderate alcohol consumption may have protective effects. Obesity in midlife is a risk factor for AD, while low BMI in late life may indicate preclinical AD. Dietary factors, such as high intake of saturated fats and cholesterol, increase AD risk, while diets rich in antioxidants and polyunsaturated fatty acids may be protective. Diabetes is associated with increased risk of dementia and AD, as is metabolic syndrome. Cerebrovascular disease, including stroke and white matter lesions, is also linked to dementia and AD. Psychosocial factors, such as low education, social isolation, and poor social engagement, increase dementia risk. Physical activity and mental stimulation are protective against dementia. Interventions targeting vascular risk factors, such as blood pressure control, and lifestyle factors, including physical activity and mental stimulation, may reduce dementia risk. Primary prevention strategies include managing vascular risk factors, maintaining social engagement, and promoting mental stimulation. Secondary prevention involves early detection and intervention, such as using biomarkers to identify preclinical AD. Multidomain interventions, including lifestyle changes and medical management, are being tested to delay dementia onset. Despite some promising findings, most primary prevention trials have not shown significant efficacy, highlighting