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UK dementia cases fell 20% between 1989 and 2011

But decline almost entirely among men; women still seem to be at higher risk, study shows

Caroline White

Wednesday, 20 April 2016

The prevalence of dementia in the UK may not be increasing as fast as has been feared, say researchers after reporting a 20% drop in the numbers of new cases diagnosed between 1989 and 2011 in a study* published online in Nature Communications.

The researchers compared the actual number of dementia cases in the UK with figures from earlier decades and previous predictions.

Between their two sample periods of 1989-94 and 2008-11, the incidence of the disease fell by 20%—but predominantly in men, among whom new cases in those over 80 almost halved during those periods, the findings show.

Two thirds of new cases will be in women, who seem to be at a higher risk of developing dementia than men, irrespective of their longevity advantage over men, the findings indicate.

But Dr Sujoy Mukherjee, a consultant psychiatrist at West London Mental Health Trust and a member of Dementia Strategic Clinical Network, London, said the researchers had failed to explain clearly why the incidence had fallen among men.

“This can’t be explained just from improved vascular risk management or lifestyle changes,” he said, adding that the diagnostic process used of a screening interview,  a geriatric mental state interview, and Mini Mental State Examination (MMSE) raises questions about the validity of the approach and therefore the figures they found.

“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.”

John Hardy, Professor of Neuroscience, UCL, said that several studies had pointed to a dropping off in the rate of dementia among the elderly despite the increases in the proportion of elderly in the population.

The Nature study was the “the most convincing of such studies” he said, but said that an important and difficult question is what lies behind this improvement in men.

“If we knew that we could perhaps improve more and help reduce the incidence in women too,” he suggested. “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.”

Gordon Wilcock, Emeritus Professor of Geralogy, University of Oxford and Honorary Consultant Physician, The 2gether NHS Foundation Trust, Cheltenham, said that the research backed other studies from different countries, and that the methods used made the findings “very robust.”

He suggested: “The greater decrease in men may relate, at least in part, to lifestyle changes, such as a reduction in the disproportionate number of men who previously smoked.”

And he added: “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 at the Alzheimer’s Society, said the findings were “encouraging”, but insisted: "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.”

* Matthews FE, et al. A two decade dementia incidence comparison from the Cognitive Function and Ageing Studies I and II. Nature Communications 7, Article number: 11398 doi:10.1038/ncomms11398

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