October 26, 2023

expert reaction to study estimating dementia prevalence by 2040

A study published in Lancet Public Health looks at the dementia incidence trend in England and Wales.

Prof Marcus Richards, Professor of Psychology in Epidemiology, MRC Unit for Lifelong Health and Ageing at UCL, University College London, said:

“This is a thorough and carefully-conducted study by a well-respected research group, based on large samples that are representative of the English older population.  Crucially, this study takes account of potential sources of bias, such as missing information due to death, increasing recognition of dementia by doctors, and people living longer.

“Particularly important is the finding that dementia has been increasing in people with lower levels of education.  As the authors acknowledge, low education may be marking a range of factors that influence risk of dementia.  We also know that education isn’t just an indication of how bright children already are when they start school, but contributes to intellectual development beyond this.”

Prof Tom Dening, Professor of Dementia Research, University of Nottingham, said:

“This is an important paper and hopefully will remind everybody that we cannot be complacent about dementia. Perhaps the figures are not too surprising as life expectancy has stopped increasing in recent years, and there has been an increase in various long-term conditions that are risk factors for dementia, such as obesity. The figures also reflect other evidence, not just from health research, that the gap between the wealthy and the poorest in our society has increased in the last decade or more. Some people might point to the UK political climate as significant in this regard. It would be interesting to see if the trends reported in this paper are mirrored in other countries with less polarised distribution of wealth and resources.

“Whether the projected figure of 1.7 million by 2040 really represents a doubling of the current figure depends on what the current numbers are, which actually we don’t precisely know. However, the point is well made by the authors that there will be a large number of cases that would not have occurred if dementia incidence had continued to fall rather than apparently increasing again.

“Another important message is how important good epidemiological studies are. They need to be supported and properly funded, otherwise we have no idea what is going on with important conditions like dementia.”

Prof Dag Aarsland, Professor of Old Age Psychiatry at King’s College London said:

“The treatment of dementia is among the most important societal challenges that we face. Despite recent positive findings suggesting that the incidence of new dementia was declining, this well-designed study, one of the first reporting more recent trends up to 2016, shows that this initial decline has reversed and the incidence is again increasing. This trend is particularly strong among people with low education. While the causes for these changes are yet unknown, these findings, suggesting that the number of people with dementia in 2040 will be 1 million,  70% higher than previous predictions, should be a call to society and researchers to intensify the work to find methods to prevent dementia. This is possible but requires a huge increased effort.”

Prof David Curtis, Honorary Professor, UCL Genetics Institute, University College London (UCL), said:

“The claim that dementia cases could be 42% higher than previously estimated by 2040 depends entirely on assuming that rates will continue to rise by 2.8% every year. I really don’t see why this should be the case. With the methods used, the estimated incidence of dementia tends to jump around quite a bit. For people aged over 75, it was 33.1 per thousand person years in 2006-2010, then fell to 23.6 in 2010-2014 and then shot back up to 29.6 in 2014-2018. It is not really plausible that the true incidence of dementia varied so dramatically in such a brief period. As the estimates for the latest period are higher than previously then if one just says there is a linear trend one will predict a large increase at some point in the future. But we’ve already seen that incidence does not follow a linear trend. And from a medical point of view I don’t see why cases should just continue to go up and up at the same rate year on year. It is true that dementia is a huge public health problem with terrible consequences but I do not think this study can tell us much about how many cases we may be seeing in 2040.”

* ‘Dementia incidence trend in England and Wales, 2002–19, and projection for dementia burden to 2040: analysis of data from the English Longitudinal Study of Ageing’ by Yuntao Chen et al. was published in Lancet Public Health at 23:30 UK time on Thursday 26 October.

Declared interests

Prof Marcus Richards: I am funded by the Medical Research Council.

Prof Tom Dening: I have no conflicting interests.

Prof Dag Aarsland: COIs – None declared

Prof David Curtis: I have no conflict of interest.

For all other experts, no reply to our request for DOIs was received.