This chapter describes modifiable risk and protective factors for dementia and will focus on so-called lifestyle changes which largely relate to the behavioural environment. Results from longitudinal observational studies have identified several possible modifiable physiological risk factors associated with both cardiovascular disease and dementia. These include increased blood pressure, central obesity and high levels of total cholesterol. The direction of these associations, however, may change over the lifespan. For instance, people in the lead up to and with dementia have shown changed profiles of these risk factors (including loss of muscle mass and weight, lowered blood pressure and a decrease in total cholesterol). It is therefore perhaps not surprising that treatment of these risk factors at a late stage has shown variable results. For optimal effects in the prevention of dementia, a lifespan approach, starting with neonatal and childhood prevention of such risk factors, as well as promoting those factors known to protect individuals from dementia is warranted.

Observational studies have suggested that smoking cessation in midlife can still significantly reduce the risk of later-life dementia. Similarly, exercise provides a low cost-effective method to improve cardiovascular disease risk parameters, but can also have direct beneficial effects on brain function. Many observational studies indicate protective effects from engaging in exercise and there may also be dose-dependent effects of engaging in physical activities in reducing dementia risk. However, meta-analyses have shown mixed effects and suggest that combined interventions (including cognitive activities) may be better for tertiary prevention. Diet, supplements and medical approaches (e.g. statins to reduce cholesterol levels) seem less effective for this kind of prevention.

Whilst risk models have been used to investigate cumulative effects of dementia risk factors, there is also a need for models including multiple protective factors, such as associations of exercise and diet together and potential offsetting of risk (e.g. poor diets) with protective factors (e.g. exercise) to better focus policies across governments to enable societies to promote a life course, which is more protective of brain health.

In sum, combining physical and psychosocial activities (exercise, cognitive stimulation) may be the best approach for prevention aimed at early and late interventions. Pathways focusing on addressing cardiovascular risk factors and nutritional deficiencies clearly need to be addressed in midlife at the latest – but preferably from the earliest stages of life, including healthy parents – to have substantial impact. A lifespan approach seems the best option for societies to reduce their population’s risk of future dementia. Currently, large trials are underway in midlife to investigate these multimodal treatments for the primary and secondary prevention of dementia. However, a societal lifespan approach starting before birth for optimal prevention of cardiovascular disease and dementia in later life is likely to pay enormous dividends for future healthy brain ageing.