The risk of developing dementia is getting smaller every year because of medical advances and people taking better care of their health, a major study has found.
Although the actual number of cases is rising as the British population increases and ages, for the average over 50, the chance of being diagnosed with diseases like Alzheimer's is falling by 2.7 per cent each year.
New research by University College London and the University of Liverpool suggests that around 700,000 people - 30,000 a year - will be spared dementia over the next two decades if progress continues as it has done since 2002.
At the start of the decade the chance of developing dementia for women was 14.3 per 1000 people and 17 in women.
But today the risk has fallen to 12.3 per 1000 for men and 14.2 for women largely because of health interventions to protect people against illness and improve overall well-being.
Dr Sara Ahmadi-Abhari, lead author from UCL said: "The decline in age-specific incidence of dementia is good news for both the individual and for the society.
"For the individual, dementia is shifted to later years is life. For society, it means the growth in numbers of people living with dementia is not as large as once anticipated."
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Around 800,000 people are currently living with dementia in Britain, according to the new research based on the English Longitudinal Study of Ageing which has followed 18,000 people in their 50s since 2002.
That number will rise substantially to 1.2 million by 2040, but crucially that increase is driven by the growing and ageing population. Without recent improvements in medicine and a shift to healthier lifestyles the figure would have been around 1.9 million in the same timescale, the experts said.
The finding was welcomed by dementia charities who said that it proved that exercising and improving heart health could ward off disease.
Dr James Pickett, Head of Research at Alzheimer’s Society described the study as a 'nugget of good news.'
"The proportion of people developing dementia at any given age has decreased slightly," he said.
"This might be due to improved cardiovascular health, or more education and physical activity and shows that dementia doesn’t have to be an inevitable part of ageing.”
However the charity warned that overall numbers were rising and called on researchers to continue to look for cures and ways to prevent the disease.
Dementia already costs Britain around £23 billion a year but that will rise dramatically in coming years, the research warns.
The study authors said the research had important policy and planning implications for the NHS and Department of Health as people live longer and deaths from other causes, such as heart disease, continue to decline.
Dr Ahmadi-Abhari, added: “Given the incidence decline, the main driver for the increase in numbers with dementia is increasing life expectancy and an increase in the proportion of the population in the oldest age groups.
"The increase in numbers of people living with dementia is nonetheless substantial and has important policy implications for planning to meet health and social care needs.
"If public health efforts fail and the risk of developing dementia does not continue to decline, the growth in numbers of people living with dementia will be much larger, reaching 1.9 million by 2040.”
The research was published in the BMJ.
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