JULY 22 – Age tells us how long we have lived but surprisingly little about how well our brains are ageing. Research is revealing remarkable differences between people of the same age, with some maintaining strong cognitive function well into later life. Explaining those differences may be one of the most important questions in brain health today.
The idea that helps explain these differences is brain resilience. It describes the brain’s ability to continue functioning well even as it faces the challenges that come with age, illness or adversity. Rather than focusing only on what changes in the brain over time, resilience asks a different question. Why do some people continue to thrive despite those changes?
One of the biggest misconceptions is that brain health becomes relevant only in old age. By then, much of the story has already been written. The foundations are laid across a lifetime, shaped by health, education, living conditions and access to care. That is why the World Health Organization defines brain health across the life course, not simply in later years.
Age can be a surprisingly poor guide to brain health. Researchers now know that people of the same age can have very different brains, and that brain scans do not always predict how well someone functions in daily life. A person whose brain appears older than expected may continue to live independently and think clearly. Another, with fewer visible changes, may struggle with everyday life.
Brain resilience offers part of the answer. Biological change does not inevitably lead to cognitive decline or loss of independence. The challenge is to understand why some people continue to lead full, independent lives despite those changes.
The evidence for this is growing. The latest Lancet Commission on dementia estimates that nearly half of dementia cases may be linked to risk factors that can be prevented or better managed across the life course. Education, hearing loss, cardiovascular health and social isolation are just some of the factors that influence how the brain ages. The story of brain ageing starts long before old age.
Our own work in the Brain Resilience Kenya study is beginning to reveal similar patterns among older adults in Kenya. One of the more surprising findings is that some people living in poverty have more stable brain structure than we would expect. This does not mean poverty is protective. A more likely explanation is survivor bias, where those who have reached older age despite years of adversity may represent an unusually resilient group.
Another unexpected finding is that some people who have experienced significant adversity show stable brain measures in regions associated with memory and emotion. The brain appears capable of adapting to repeated challenges in ways we are only beginning to understand. None of this should be mistaken for evidence that chronic stress is beneficial. Its effects on health are well established, even if the brain sometimes shows remarkable capacity to adapt.
Wearable devices are adding another dimension to this picture. Sleep, heart rate and daily movement offer a window into how the brain and body respond to the demands of everyday life. Brain resilience is reflected not only in memory or thinking, but also in these everyday rhythms.
Perhaps the most important lesson is that there is no single way to grow older. By the time people reach later life, their brains reflect decades of experience and adversity. That helps explain why two people of the same age can have very different brain health.
If we accept that brain health is shaped across a lifetime, then our response must begin long before old age. Investing in education, reducing poverty, improving cardiovascular health and strengthening social connections are not simply good public health measures, but investments in healthier brains and better ageing.
The writer is a Post-Doctoral Fellow at the Aga Khan University’s Brain and Mind Institute.
