An interview with a researcher in the field: "the reality is that our brains age throughout life and, in fact, the science tells us that at age 45 we can measure cognitive and memory decline in the average person. There's a steady gradual decline that continues. ... Age is the greatest risk factor. By age 65 or older, your risk is about 10 per cent for Alzheimer's dementia. By 85, it's 40 per cent or more. The implications are that we have a lot more people who have dementia and a lot more people concerned about developing it. ... The studies of successful aging tell us that, when it comes to cognitive success or avoiding dementia or developing it, for the average person only a third of what determines that cognitive outcome results from genetics, from what we inherit. Rarely there are families, less than 2 per cent of cases, with very strong genetic components; they have mutations that cause the disease very early in life. For the vast majority, the genetics are not as strong. They are a factor. About 20 per cent of the population has this risk. It increases the likelihood of getting the disease and the likelihood of getting it at an earlier age but it's not 100 per cent. That means that two-thirds of the formula comes from non-genetic factors: the lifestyle choices we make every day have a major impact on how well our brains age. ... Physical exercise, mental exercise, nutrition, stress management and other behaviours, like avoiding head trauma, not smoking and so forth. ... Exercise seems obvious [but] it may not be completely obvious for people. They know there is a connection between exercise and physical health, exercise and avoiding heart disease. But not everybody is aware of the strong connection between physical exercise and brain health."