Hundreds of thousands of people could ward off dementia by adopting a healthy lifestyle, a major study has found.
Some 40 per cent of cases could be avoided or delayed, a comprehensive review of the evidence concludes.
Eating less, exercising more, and cutting out alcohol and cigarettes significantly reduce the risk of developing dementia in later life, researchers said.
These lifestyle habits – together with environmental factors, medical history and education – are responsible for roughly 340,000 out of Britain’s 850,000 dementia cases, the study suggests.
A team of 28 world-leading dementia experts, who conducted the review for the Lancet medical journal, identified 12 different controllable factors which contribute to dementia risk.
For decades experts believed dementia was a matter of fate – a cruel quirk of genetics and ageing.
But in recent years scientists have become increasingly aware that dementia is not inevitable, and in fact the way people live their lives increases the risk of developing the condition in old age.
There is now a growing understanding that poor blood circulation – which is hugely influenced by diet, exercise and drinking – has a significant impact on the brain.
Education is also now known to have a protective effect, with those who receive a better schooling more likely to continue to carry out complex thinking throughout their lives – which reduces dementia risk by keeping the brain active.
Air pollution, as well as depression and social in old age, also increases the risk.
In 2017 a previous Lancet review identified nine elements which contributed to dementia risk.
The new paper updates this and adds three new risk factors – alcohol intake, air pollution and head injuries.
The researchers – who include world-leading British scientists from University College London, Cambridge, Exeter, Edinburgh and Manchester – stressed that the majority of dementia risk is down to genetics and other uncontrollable factors.
But they said the new findings show people have a huge degree of power to determine their own fate.
Politicians, meanwhile, must take responsibility for reducing some of the risk, they said – particularly by addressing the growing problem of air pollution.
Researcher Professor Clive Ballard of the University of Exeter, said: ‘Our findings present an exciting opportunity to improve millions of lives across the world by preventing or delaying dementia, through healthier lifestyle to include more exercise, being a healthy weight and stopping smoking, and good medical treatment of risk factors like high blood pressure.
‘One important less well known risk factor is hearing loss in mid-life, with emerging evidence that wearing hearing aids may be protective.
‘This presented an important public health message – if you’re having hearing problems, getting tested in mid life and wearing a hearing aid if needed could have multiple benefits.
‘This analysis shows there’s real potential to improve brain health by taking action.’
The researchers said one of the biggest controllable factors is poor education, which is responsible for 7 per cent of dementia cases.
Hearing loss in middle age is responsible for 8 per cent of cases and brain injury for 3 per cent.
High blood pressure from middle age contributes 2 per cent, obesity 1 per cent and drinking more than 21 units a week 1 per cent.
Smoking in old age contributes 5 per cent of cases, physical inactivity 2 per cent, diabetes 1 per cent, depression 4 per cent, isolation 4 per cent and air pollution 2 per cent.
Study leader Professor Gill Livingston of UCL, who presented the paper yesterday to the Alzheimer’s Association International Conference, said politicians could do much to reduce these risks.
‘Our report shows that it is within the power of policy-makers and individuals to prevent and delay a significant proportion of dementia, with opportunities to make an impact at each stage of a person’s life.
‘We can reduce risks by creating active and healthy environments for communities, where physical activity is the norm, better diet is accessible for all, and exposure to excessive alcohol is minimised.’
Fiona Carragher, director of research at the Alzheimer’s Society, which part-funded the study, said: ‘While we don’t have all the answers yet, we can take action now to tackle the risk factors within our control, including excessive drinking, obesity and high blood pressure.
‘Meanwhile, we need public health policies to address other factors, such as air pollution and inequalities in childhood education.’
Dr Rosa Sancho, head of research at Alzheimer’s Research UK, added: ‘While there’s no sure-fire way of preventing dementia, the best way to keep your brain healthy as you age is to stay physically and mentally active, eat a healthy balanced diet, not smoke, drink only within the recommended limits and keep weight, cholesterol and blood pressure in check.
‘With no treatments yet able to slow or stop the onset of dementia, taking action to reduce these risks is an important part of our strategy for tackling the condition.
‘This report underlines the importance of acting at a personal and policy level to reduce dementia risk.’
Professor Jennifer Rusted of the University of Sussex, added: ‘The big picture here is that an individual’s dementia risk is a complex of many factors that impact differently through the lifespan, and lifestyle choices and changes can quite significantly reduce risk of dementia in later life.
‘If you can work to mitigate any of these multiple factors then you can at least push back the age at which cognitive impairment emerges to affect your independent living and quality of life.’