Lancet Commission on dementia prevention, intervention and care56 suggest that addressing modifiable risk factors might prevent or delay up to 40% of dementia cases. Overview 15 Modifiable risk factors have been the subject of much research. In addition to The Lancet Commission report,56 the 2019 World Health Organization (WHO) recommendations94 to reduce risk of cognitive decline and dementia, an Alzheimer’s Association article95 evaluating the effects of modifiable risk factors on cognitive decline and dementia, and a report from the National Academy of Medicine96 all point to the promising role of addressing these risk factors to reduce risk of dementia and cognitive decline. This section focuses on risk factors common to these reports. It is important to note that “reducing risk” of cognitive decline and dementia is not synonymous with preventing cognitive decline and dementia altogether. Individuals who take measures to reduce risk may still develop dementia, but they may develop it later in life than they would have if they had not taken steps to reduce their risk. It is also important to note that factors that increase or decrease the risk of cognitive decline and dementia may not necessarily do so by directly affecting the brain changes associated with Alzheimer’s disease.79 For example, it is possible that smoking may contribute to cerebrovascular disease, which in turn increases the risk of dementia, but smoking may not directly contribute to the development of the amyloid plaques and tau tangles that characterize Alzheimer's disease. Cardiovascular Disease Risk Factors, Physical Activity and Diet Brain health is affected by the health of the heart and blood vessels. Although it makes up just 2% of body weight, the brain consumes 20% of the body’s oxygen and energy supplies.97 A healthy heart ensures that enough blood is pumped to the brain, while healthy blood vessels enable the oxygen- and nutrient-rich blood to reach the brain so it can function normally. Many factors that increase the risk of cardiovascular disease are also associated with a higher risk of dementia, particularly dementia due to cerebrovascular disease (i.e., vascular dementia).98 These factors include smoking99-104 and diabetes.105-108 The specific mechanisms linking diabetes and dementia are unclear but may be numerous, potentially involving aspects of insulin resistance.109-110 The age at which some risk factors develop appears to affect dementia risk. For example, midlife obesity,111-115 hypertension,82,111,116-119 prehypertension (systolic blood pressure from 120 to 139 mm Hg or diastolic pressure from 80 to 89 mm Hg)82 and high cholesterol120 are associated with an increased risk of dementia. In contrast to midlife obesity, late-life obesity121 and hypertension onset after age 80122 are associated with decreased risk of dementia. It is possible that the disease causing dementia affects body mass and blood pressure rather than the reverse. More research is needed to understand why the effects of some modifiable risk factors may change with age. Building on the connection between heart health and brain health, researchers have found that factors that protect the heart may also protect the brain and reduce the risk of developing dementia. Physical activity123-135 appears to be one of these factors. Although researchers have studied a wide variety of physical activities, they do not know which specific types, what frequency or what duration of physical activity may be most effective in reducing risk. In addition to physical activity, emerging evidence suggests that consuming a heart-healthy diet may be associated with reduced dementia risk.136-143 A heart-healthy diet emphasizes fruits, vegetables, whole grains, fish, chicken, nuts, legumes and healthy fats such as olive oil while limiting saturated fats, red meat and sugar. Examples of heart-healthy diets are the Mediterranean, DASH (Dietary Approaches to Stop Hypertension) and MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diets.144-146 A systematic review147 of the use of supplements, including vitamins C, D and E, omega-3 fatty acids and ginkgo biloba, found little to no benefit in preventing cognitive decline, MCI or Alzheimer’s dementia. Researchers have begun studying combinations of health factors and health behaviors (for example, blood pressure as a health factor and physical activity as a health behavior) to learn whether combinations of risk factors better identify Alzheimer’s and dementia risk than individual risk factors. They are also studying whether intervening on multiple risk factors simultaneously is more effective at reducing risk than addressing a single risk factor. While two multidomain studies did not find clear cognitive benefits,148-149 the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER)150 showed slower cognitive decline among high-risk individuals assigned to a multidomain lifestyle intervention The success of FINGER has led to the launch of multidomain intervention studies in other countries, including the Alzheimer's Association U.S. Study to Protect Brain Health Through Lifestyle Intervention to Reduce Risk (U.S. POINTER).151 Education and Educational Opportunities People with more years of formal education are at lower risk for Alzheimer’s and other dementias than