14 July 2014 Last updated at 00:54
One in three Alzheimer's cases preventable, says research
One in three cases of Alzheimer's disease worldwide is preventable, according to research from the University of Cambridge.
The main risk factors for the disease are a lack of exercise, smoking, depression and poor education, it says.
Previous research from 2011 put the estimate at one in two cases, but this new study takes into account overlapping risk factors.
Alzheimer's Research UK said age was still the biggest risk factor.
Writing in The Lancet Neurology, the Cambridge team analysed population-based data to work out the main seven risk factors for Alzheimer's disease.
Low educational attainment
They worked out that a third of Alzheimer's cases could be linked to lifestyle factors that could be modified, such as lack of exercise and smoking.
The researchers then looked at how reducing these factors could affect the number of future Alzheimer's cases.
They found that by reducing each risk factor by 10%, nearly nine million cases of the disease could be prevented by 2050.
In the UK, a 10% reduction in risk factors would reduce cases by 8.8%, or 200,000, by 2050, they calculated.
Current estimates suggest that more than 106 million people worldwide will be living with Alzheimer's by 2050 - more than three times the number affected in 2010.
Healthier old age
Prof Carol Brayne, from the Institute of Public Health at the University of Cambridge, said: "Although there is no single way to treat dementia, we may be able to take steps to reduce our risk of developing dementia at older ages.
"We know what many of these factors are, and that they are often linked.
"Simply tackling physical inactivity, for example, will reduce levels of obesity, hypertension and diabetes, and prevent some people from developing dementia.
"As well as being healthier in old age in general, it's a win-win situation."
Dr Simon Ridley, head of research at charity Alzheimer's Research UK, said there was still much to discover about the disease.
"While age is the biggest risk factor for most cases of Alzheimer's, there are a number of lifestyle and general health factors that could increase or decrease a person's chances of developing the disease.
"However, we still do not fully understand the mechanisms behind how these factors are related to the onset of Alzheimer's."
Dr Ridley said there were more than 820,000 people in the UK living with dementia, and an ageing population would lead to spiralling numbers being affected.
"As there is still no certain way to prevent Alzheimer's, research must continue to build the strongest evidence around health and environmental factors to help individuals reduce their risk."
He added: "This new study also highlights that many cases are not due to modifiable risk factors which underlines the need to drive investment into new treatment research."
Of the seven risk factors, the largest proportion of cases of Alzheimer's in the US, UK and the rest of Europe can be attributed to physical inactivity.
The study says about a third of the adult population in these countries are physically inactive.
Physical inactivity is also linked to increased risks of other health problems, such as cancers and cardiovascular diseases.
The Lancet Neurology, Volume 13, Issue 8, Pages 788 - 794, August 2014
doi:10.1016/S1474-4422(14)70136-XCite or Link Using DOI
This article can be found in the following collections: Public Health; Cardiology & Vascular Medicine (Hypertension); Endocrinology (Diabetes); Neurology (Dementias); Nutrition & Metabolism (Obesity)
Copyright c 2014 Elsevier Ltd All rights reserved.
Potential for primary prevention of Alzheimer's disease: an analysis of population-based data
Sam Norton PhD a, Fiona E Matthews PhD b, Deborah E Barnes PhD c d f, Prof Kristine Yaffe MD c d e f, Prof Carol Brayne MD g Corresponding AuthorEmail Address
Recent estimates suggesting that over half of Alzheimer's disease burden worldwide might be attributed to potentially modifiable risk factors do not take into account risk-factor non-independence. We aimed to provide specific estimates of preventive potential by accounting for the association between risk factors.
Using relative risks from existing meta-analyses, we estimated the population-attributable risk (PAR) of Alzheimer's disease worldwide and in the USA, Europe, and the UK for seven potentially modifiable risk factors that have consistent evidence of an association with the disease (diabetes, midlife hypertension, midlife obesity, physical inactivity, depression, smoking, and low educational attainment). The combined PAR associated with the risk factors was calculated using data from the Health Survey for England 2006 to estimate and adjust for the association between risk factors. The potential of risk factor reduction was assessed by examining the combined effect of relative reductions of 10% and 20% per decade for each of the seven risk factors on projections for Alzheimer's disease cases to 2050.
Worldwide, the highest estimated PAR was for low educational attainment (19・1%, 95% CI 12・3?25・6). The highest estimated PAR was for physical inactivity in the USA (21・0%, 95% CI 5・8?36・6), Europe (20・3%, 5・6?35・6), and the UK (21・8%, 6・1?37・7). Assuming independence, the combined worldwide PAR for the seven risk factors was 49・4% (95% CI 25・7?68・4), which equates to 16・8 million attributable cases (95% CI 8・7?23・2 million) of 33・9 million cases. However, after adjustment for the association between the risk factors, the estimate reduced to 28・2% (95% CI 14・2?41・5), which equates to 9・6 million attributable cases (95% CI 4・8?14・1 million) of 33・9 million cases. Combined PAR estimates were about 30% for the USA, Europe, and the UK. Assuming a causal relation and intervention at the correct age for prevention, relative reductions of 10% per decade in the prevalence of each of the seven risk factors could reduce the prevalence of Alzheimer's disease in 2050 by 8・3% worldwide.
After accounting for non-independence between risk factors, around a third of Alzheimer's diseases cases worldwide might be attributable to potentially modifiable risk factors. Alzheimer's disease incidence might be reduced through improved access to education and use of effective methods targeted at reducing the prevalence of vascular risk factors (eg, physical inactivity, smoking, midlife hypertension, midlife obesity, and diabetes) and depression.
National Institute for Health Research Collaboration for Leadership in Applied Health Research and Care for Cambridgeshire and Peterborough.
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