But healthy habits, including doing at least 150 minutes of moderate exercise per week and not smoking, could make a big difference. The study was the first to consider both genetic and lifestyle risk factors and included data from the UK Biobank on almost 200,000 adults aged 60 or over and of European ancestry. Some 1,769 developed dementia during an eight-year follow-up period.
The participants were categorised as having a low, intermediate or high genetic risk, and a favourable, intermediate or unfavourable lifestyle.
All were around a third less likely to develop dementia if they followed a favourable lifestyle, compared with an unhealthy one.
Crucially, the effect was similar even for people whose genes put them at higher risk –those who lived a healthy lifestyle were 32 per cent less likely to develop dementia.
Joint lead author Dr David Llewellyn, of the University of Exeter Medical School and the Alan Turing Institute, said: “This research delivers a very important message that undermines a fatalistic view of dementia. Some people believe it’s inevitable they’ll develop dementia because of their genetics.
“However it appears you may be able to substantially reduce your dementia risk by having a healthy lifestyle.”
The researchers defined a favourable lifestyle as one which included regular exercise and a balanced diet with more than three portions of fruit and vegetables a day, two portions of fish per week and little processed meats.
It also involved not smoking and moderate alcohol consumption of no more than one pint of beer a day.
A family history of the disease is known to increase risk of dementia, but until now it was unknown whether that risk could be offset.
Dr Carol Routledge of Alzheimer’s Research UK warned that some people who live healthily will still develop the disease.
She said: “While we can’t change the genes we inherit, this research shows that changing our lifestyle can still help to stack the odds in our favour.”
The findings were presented yesterday at the Alzheimer’s Association International Conference in Los Angeles.
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