The strongest evidence on protecting your brain points to a rule of thumb that sounds almost too simple: what's good for your heart is good for your brain. Alzheimer's Research UK notes that while most people connect exercise, diet and not smoking to cardiovascular health, far fewer realise the same habits shape brain health. Staying active keeps blood moving, delivering oxygen and nutrients to the brain, and research suggests the brains of regular exercisers show less damage to their small blood vessels. The NHS also points to endorphins released during exercise as a boost to mental wellbeing.
Two studies illustrate the point. In a US study of more than 2,000 people over 65, volunteers reported their diets, physical activity and how often they did mentally stimulating activities. Those who scored well on all three lived longer, and among those who did go on to develop Alzheimer's, the disease tended to arrive at an older age. A Chinese study that followed 500,000 people for a decade found that ordinary activity counted: walking for pleasure, DIY and housework were all linked to lower dementia risk. Elite fitness is not the threshold.
Timing matters as much as the habits themselves. Brain changes associated with Alzheimer's can begin decades before memory or thinking problems appear, which is why the 30s, 40s and 50s are considered a particularly important window. The Insight 46 study found that blood pressure changes in the 40s and 50s were associated with more signs of blood vessel damage in the brain by the 70s - damage accumulating silently across thirty years.
The practical implication is less about overhauling your life than about sustainability. Alzheimer's Research UK frames physical activity broadly, from dancing in the kitchen to walking instead of catching the bus, and suggests finding healthier versions of meals you already like rather than adopting an unfamiliar diet. Habits people enjoy are the ones they keep, and duration is what the evidence rewards. Research also links diets high in saturated fat and sugar to raised risk of both heart disease and dementia.