Dementia Roots in Childhood, Lifelong Prevention Key
More than 60 million people are estimated to be living with dementia, resulting in over 1.5 million deaths a year and an annual cost to the global healthcare economy of around US $1.3 trillion (almost £1 trillion).
Despite decades of scientific research and billions of pounds of investment, dementia still has no cure. But what of the old saying that prevention is better than cure? Is preventing dementia possible? And if so, at what age should we be taking steps to do so?
Despite what many believe, dementia is not simply an unavoidable consequence of ageing or genetics. It is estimated that up to 45% of dementia cases could potentially be prevented by reducing exposure to 14 modifiable risk factors common throughout the world.
Many of these risk factors – which include things like obesity, lack of exercise, and smoking – are traditionally studied from middle age (around 40 to 60 years old) onwards. As a result, several of the world’s leading health bodies and dementia charities now recommend that strategies aimed at reducing dementia risk should ideally be targeted at this age to reap the greatest benefits.
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We argue , however, that targeting even younger ages is likely to provide greater benefits still. But how young are we talking? And why would exposure to risk factors many decades before the symptoms of dementia traditionally appear be important?
To explain, let’s work backwards from middle age, starting with the three decades covering adolescence and young adulthood (from ten to 40 years old).
Many lifestyle-related dementia risk factors emerge during the teenage years, then persist into adulthood. For example, 80% of adolescents living with obesity will remain this way when they are adults. The same applies to high blood pressure and lack of exercise . Similarly, virtually all adults who smoke or drink will have started these unhealthy habits in or around adolescence.
This poses two potential issues when considering middle age as the best starting point for dementia-prevention strategies. First, altering health behaviour that has already been established is notoriously difficult. And second, most high-risk individuals targeted in middle age will almost certainly have been exposed to the damaging effects of these risk factors for many decades already.
As such, the most effective actions are likely to be those aimed at preventing unhealthy behaviour in the first place, rather than attempting to change long-established habits decades down the line.
But what about even earlier in people’s lives? Could the roots of dementia stretch as far back as childhood or infancy? Increasing evidence suggests yes, and that risk factor exposures in the first decade of life (or even while in the womb) may have lifelong implications for dementia risk.
To understand why this may be, it’s important to remember that our brain goes through three major periods during our lives – development in early life, a period of relative stability in adult life, and decline (in some functions) in old age.
Most dementia research understandably focuses on changes associated with that decline in later life. But there is increasing evidence that many of the differences in brain structure and function associated with dementia in older adults may have at least partly existed since childhood.
For example, in long-term studies where people have had their cognitive ability tracked across their whole lives, one of the most important factors explaining someone’s cognitive ability at age 70 is their cognitive ability when they were 11. That is, older adults with poorer cognitive skills have often had these lower skills since childhood, rather than the differences being solely due to a faster decline in older age.
Similar patterns are also seen when looking for evidence of dementia-related damage on brain scans , with some changes appearing to be more closely related to risk factor exposures in early life than current unhealthy lifestyles.
Taken together, perhaps the time has come for dementia prevention to be thought of as a lifelong goal, rather than simply a focus for old age.
But how do we achieve this in practical terms? Complex problems require complex solutions, and there is no quick fix to address this challenge. Many factors contribute to increasing or decreasing an individual’s dementia risk – there is no “one size fits all” approach.
But one thing generally agreed upon is that mass medication of young people is not the answer. Instead, we – along with 33 other leading international researchers in the field of dementia – recently published a set of recommendations for actions that can be taken at the individual, community and national levels to improve brain health from an early age.
Our consensus statement and recommendations deliver two clear messages. First, meaningful reductions in dementia risk for as many people as possible will only be achievable through a coordinated approach that brings together healthier environments, better education and smarter public policy.
Second – and perhaps most importantly – while it’s never too late to take steps to reduce your risk of dementia, it’s also never too early to start.
Scott Chiesa receives funding from an Alzheimer’s Research UK David Carr Fellowship.
Francesca Farina receives funding from the Alzheimer’s Association and the University of Chicago.
Laura Booi does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.