The number of people with dementia – both new cases and total numbers with the disease – appears to be stabilising in some Western European countries despite populations ageing, in direct contrast to the ‘dementia epidemic’ reported in some recent studies. Professor Carol Brayne and Yu-tzu Wu from the Cambridge Institute of Public Health explore what this means.
The notion of a dementia epidemic has been a big concern in ageing societies across the globe for some time. With the extension of life expectancy it seems to be an inevitable disaster – one of the “greatest enemies of humanity”, according to UK prime minister David Cameron.
Many shocking figures have been published pointing to dramatic increases in dementia prevalence and massive predicted costs and burdens. Yet new evidence seems to suggest otherwise. In a review of dementia occurrence in five studies in the UK, Sweden, Spain and the Netherlands between 2007 and 2013 that used consistent research methods and diagnostic criteria, we found none that supported headlines about dramatic increases in dementia. They report stable or reduced prevalence at specific ages over the past few decades – despite ageing populations.
How to reconcile this relatively optimistic picture with what looks like panic on the part of governments, charities and the mainstream media? One reason is that they fail to recognise the complexity of dementia diagnosis. The main criteria for diagnosing dementia hinge on cognitive decline and an associated deterioration in a person’s ability to carry out day-to-day activities. If there are variations in the recognised boundaries of these criteria either in different countries or during different time periods, this can affect occurrence estimates without changing the fundamentals of the dementia syndrome itself.
Over the past few decades, the diagnostic criteria have indeed changed across the world in parallel with public awareness and perceptions. More people are now diagnosed with very early dementia, for example, though it may or may not progress into more severe forms. The introduction of biomarkers for diagnosis is likely to further expand prevalence by identifying large sections of populations at risk – and is already in its early stages. Such changes will affect different groups of people in different contexts in different ways, but basically we might be counting more people as having dementia due to the use of more inclusive diagnostic criteria.
Solution and salvation
Having said that, there might be more than careless use of research evidence at play. The worsening epidemic message also fits well with consumer psychology and the recent history of over-medicalisation: fear, demand for a solution, and salvation. The world is looking for a silver bullet. Since the G8 summit of 2013, the hunt for “a dementia cure or disease-modifying therapy by 2025” has become a global target. We have seen major investment from public and private funding bodies alike, stimulating national and even global collaborations. Current research has focused on drug interventions and clinical trials, as well as relevant biomarkers including novel imaging for assumed brain pathology.
The progress to date has not been promising, but the reality is that healthcare and pharmaceutical companies are looking at large potential profits from future dementia interventions. It makes sense for them to play up the possibility of avoiding conditions associated with ageing, both now and in future. It would be particularly lucrative for them to be able to recommend specific medications for younger people who had been found to have a higher risk of developing dementia later in life. Such treatments could enjoy far wider demand than a specific targeted cure for the smaller group who are already developing the condition.
But if dementia prevalence is indeed stable or even declining, might past policies provide a better answer? Remember we are talking about a generation which experienced substantial post-war investments in education and socialised healthcare, and a partial reduction in social inequalities as a result. If it has worked thus far, the same kind of approach might be the best way forward for the future. Adopting a drug-only approach is likely to lead to widening inequalities of access and problems with affordability, as we learned with HIV/AIDS, cancer and other diseases.
The current dementia prevention advice focuses on what people can do in terms of healthy behaviour and lifestyle: exercise, diet and so forth. Yet our lifestyles and health are considerably influenced by factors in our wider social environment over which we have limited control. For the sake of future populations, this is why responsibility for dementia prevention should be seen as a matter for society and the world as a whole.
Source: Yu-Tzu Wu – University of Cambridge Image Source: The image is in the public domain Original Research:Abstract for “Dementia in western Europe: epidemiological evidence and implications for policy making” by Yu-Tzu Wu, MSc, Prof Laura Fratiglioni, PhD, Prof Fiona E Matthews, PhD, Prof Antonio Lobo, MD, Prof Monique M B Breteler, PhD, Prof Ingmar Skoog, PhD, and Prof Carol Brayne, in The Lancet Neurology. Published online August 20 2015 doi:10.1016/S1474-4422(15)00092-7
Dementia in western Europe: epidemiological evidence and implications for policy making
Dementia is receiving increasing attention from governments and politicians. Epidemiological research based on western European populations done 20 years ago provided key initial evidence for dementia policy making, but these estimates are now out of date because of changes in life expectancy, living conditions, and health profiles. To assess whether dementia occurrence has changed during the past 20–30 years, investigators of five different studies done in western Europe (Sweden [Stockholm and Gothenburg], the Netherlands [Rotterdam], the UK [England], and Spain [Zaragoza]) have compared dementia occurrence using consistent research methods between two timepoints in well-defined geographical areas. Findings from four of the five studies showed non-significant changes in overall dementia occurrence. The only significant reduction in overall prevalence was found in the study done in the UK, powered and designed explicitly from its outset to detect change across generations (decrease in prevalence of 22%; p=0·003). Findings from the study done in Zaragoza (Spain) showed a significant reduction in dementia prevalence in men (43%; p=0·0002). The studies estimating incidence done in Stockholm and Rotterdam reported non-significant reductions. Such reductions could be the outcomes from earlier population-level investments such as improved education and living conditions, and better prevention and treatment of vascular and chronic conditions. This evidence suggests that attention to optimum health early in life might benefit cognitive health late in life. Policy planning and future research should be balanced across primary (policies reducing risk and increasing cognitive reserve), secondary (early detection and screening), and tertiary (once dementia is present) prevention. Each has their place, but upstream primary prevention has the largest effect on reduction of later dementia occurrence and disability.
“Dementia in western Europe: epidemiological evidence and implications for policy making” by Yu-Tzu Wu, MSc, Prof Laura Fratiglioni, PhD, Prof Fiona E Matthews, PhD, Prof Antonio Lobo, MD, Prof Monique M B Breteler, PhD, Prof Ingmar Skoog, PhD, and Prof Carol Brayne, in The Lancet Neurology. Published online August 20 2015 doi:10.1016/S1474-4422(15)00092-7