We often talk about dementia as though it is something that arrives suddenly in later life. In reality, brain health is shaped over decades by how we live, learn, connect and stay engaged. Education matters, but not only in the formal sense. A brain that keeps learning, solving, adapting and interacting is a brain that is being exercised. The World Health Organization lists low educational attainment, cognitive inactivity and social isolation among the risk factors for cognitive decline and dementia, while research on cognitive reserve suggests that mentally stimulating lives help the brain stay resilient for longer.

That makes sense when you consider just how demanding the brain is. It makes up only about 2% of body weight, yet it uses roughly 20% of the body’s energy at rest. Even when we look as though we are doing nothing, the brain is still active, processing signals, updating information and keeping the system running. In other words, the brain is not built for idling. It is built for constant work.

A great deal of that work is social. Much of everyday brain activity is spent interpreting other people: reading facial expressions, tone, motives, trust, humour, status and risk. Neuroscience research on the brain’s default mode network shows strong links with self-reflection and social understanding. So when we are in conversation, managing relationships, reading the room or trying to work out what someone really means, we are not doing something “light”. We are putting the brain to work in one of the most natural and demanding ways possible.

This is one reason ageing can become tricky if life grows too narrow or too repetitive. As routines settle in and patterns of behaviour become fixed, there are often fewer built-in reasons to solve new problems or stretch ourselves. We can start living on autopilot without realising it. Familiarity feels comfortable, but too much sameness can mean less novelty, less challenge and less mental effort.

For many people, retirement is where this shift becomes most obvious. Work does more than fill time. It gives us deadlines, decisions, reading, planning, problem solving, incidental conversations and the daily need to navigate different personalities and situations. When that disappears, the drop in cognitive load can be significant unless it is replaced deliberately. The National Institute on Aging notes that retirement can leave people more vulnerable to social isolation and loneliness, and research on retirement networks suggests that work-related ties often fall away, even when family ties remain strong.

That is why “educating the brain” needs to continue well beyond school or work. It means reading deeply, learning new skills, joining groups, volunteering, mentoring, taking classes, playing music, doing strategy-based hobbies, travelling, having stimulating conversations and staying involved in community life. Meaningful activity with other people does more than lift mood. It keeps the brain engaged in memory, language, judgement, emotional reading and decision-making. Research suggests these kinds of activities support wellbeing and may also help maintain cognitive function as we age.

The goal is not to stay busy for the sake of it. The goal is to stay mentally alive. Retirement should not mean cognitive withdrawal. It should mean replacing the complexity that work once provided with other forms of purpose, challenge and connection. A well-educated brain is not just one that once studied hard. It is one that keeps being used.

In the end, protecting brain health is less about one miracle habit and more about the overall shape of life. Keep learning. Keep connecting. Keep solving. Keep participating. The brain responds to use, and the more reasons we give it to stay switched on, the better chance we give ourselves of staying sharper for longer.