In a new study, published in Nature Communications, researchers compared the actual number of dementia cases in the UK to earlier decades and previous predictions. They report a 20% drop in incidence of dementia between their two samples (1989-1994, 2008-2011) which they attribute mainly to a reduction in men. These comments accompanied a briefing.
Dr. Sujoy Mukherjee, Consultant Psychiatrist, West London Mental Health Trust and a Member of Dementia Strategic Clinical Network, London, said:
“This is a most interesting paper exploring an issue which is obviously very sensitive. This is a robust piece of research but I would like to comment on three issues.
“The key finding of 20% drop in incidence rate is mostly contributed by almost halving of incidence rate among men over 80 years of age (Table 1, CFASI vs CFAS II). The authors have not provided any clear explanation of this finding. This can’t be explained just from improved vascular risk management or lifestyle changes.
“The process of diagnosis is not very clear except a screening interview, a geriatric mental state interview and Mini Mental State Examination (MMSE). While the authors have argued in favour of such approach longitudinally, the diagnostic process itself falls far short of standard practice in most studies and even clinical practice in any centre of repute. This inherently raise a question about validity of diagnosis of dementia in this study and hence the incidence figures and conclusion.
“The authors have also concluded that a lot of their patients were in an advanced state of dementia and hence were unable to answer a lot of questions. This is in contrast to experience in current clinical practice across the country where patients are referred much earlier and get the diagnosis of dementia at an early stage of their illness. So, the findings in this paper may be potentially undermined by the fact that the time of the study and absence of a robust protocol may have missed a number of patients who would have received a diagnosis of dementia in current day clinical practice.”
Prof. John Hardy, Professor of Neuroscience, UCL, said:
“There have been a number of studies suggesting that the rate of dementia in the elderly is dropping although the number of elderly is increasing (so the overall number of sufferers is staying relatively flat). This study is the most convincing of such studies and seems to show that this improvement over the last 20 years is restricted to men. An important and difficult question is what is behind this improvement: if we knew that we could perhaps improve more and help reduce the incidence in women too. The most obvious changes relate to vascular health… smoking cessation and blood pressure and cholesterol control. Clearly, these issues deserve further careful study, but this study suggests some good news.”
Prof. Gordon Wilcock, Emeritus Professor of Geratology, University of Oxford and Honorary Consultant Physician, The 2gether NHS Foundation Trust, Cheltenham, said:
“The methodology used by Professor Brayne’s group make the findings reported very robust, as does the fact that it is in line with similar data from different countries.
“People in the UK are less likely than has been predicted to develop dementia, and overall numbers less likely to increase as significantly as has been predicted, unless adverse lifestyle factors and co-morbidities such as diabetes intervene.
“The greater decrease in men may relate, at least in part, to life style changes, such as a reduction in the disproportionate number of men who previously smoked.
“Although we will never completely remove the risk of developing dementia, living healthier lifestyles from as early as possible will reduce that risk, or delay its onset.
“The most important finding from this study is that changing our approach to how we live our lives is as important as developing drugs to treat dementia. This is our individual responsibility, not anyone else’s.”
Dr James Pickett, Head of Research, Alzheimer’s Society said:
“It’s encouraging to see research showing that the number of new cases of people with dementia in the UK has fallen, indicating that lifestyle factors, such as better heart health, are helping to reduce the risk of dementia. However, people are living for longer and with other risk factors such as diabetes and obesity on the rise, there will still be over 200,000 new cases of dementia each year. That’s still an enormous number of people who require better information and health and social care support.
“The study indicates two thirds of new cases of dementia will be in women – this is in part due to the fact that women live longer, but it also appears that women are at a higher risk of developing dementia. Over the past 20 years the most significant change appears to have been a reduction in the rates of dementia amongst men.
“Since this study began in 1989, there have substantial improvements in our understanding of dementia and many people are now being diagnosed at an earlier stage of the condition. It’s possible, therefore, that not all of these people would be identified using the methods of this study, leading to an underestimate of people with dementia.”
Dr Simon Ridley, Director of Research, Alzheimer’s Research UK, said:
“This is welcome news, but with hundreds of thousands still affected by dementia and no treatments to slow the diseases that cause it, we cannot be complacent. A growing body of evidence is now telling us that dementia risk across the population can change over time: an important reminder that dementia is not inevitable and can be fought. The challenge for research now is to understand what has driven the reduction, so that we can capitalise on this knowledge and take action to prevent incidence rates rising again in future. Further research is also vital to determine why the reduction has been greater for men than for women, and how we can address this imbalance.
“These important results reveal how the picture has changed since the early 1990s to today, but several factors may affect dementia incidence rates in the future. The UK currently has rising levels of obesity and diabetes, both of which are risk factors for dementia, and continued efforts to improve public health will be crucial to ensure that this trend in falling dementia incidence is not slowed or reversed. We must also remember that there are currently no certain ways to prevent dementia, and investment in research to find better preventions and new treatments remains a priority. There are still huge numbers of people living with dementia in the UK today and the need to help them, and future generations, is just as great as ever.”
‘A two decade dementia incidence comparison from the Cognitive Function and Ageing Studies I and II’ by Matthews et al. published in Nature Communications on Tuesday 19th April.
Dr Mukherjee: “I do not have any conflict of interest in relation to this paper and my response.”
Prof. Hardy: “Consulting – Eisai Pharmaceuticals”
Prof. Wilcock: “I have no conflict of interests to declare.”
Dr Pickett: None received
Dr Ridley: “No interests to declare”