Excessive drinking and exposure to pollution are among the risk factors.
A report by the Lancet Commission on dementia prevention, intervention and care estimates that up to 40 per cent of dementia cases worldwide could be delayed or prevented by addressing 12 lifestyle factors.
Previous studies had found that a third of dementia cases could be prevented by addressing nine lifestyle factors including midlife hearing loss, depression, less childhood education and smoking.
The new report adds a further three risk factors to the list: excessive midlife alcohol intake, midlife head injuries and exposure to air pollution in older age.
“Dementia is potentially preventable – you can do things to reduce your risk of dementia, whatever stage of life you are at,” said Gill Livingston, professor of psychiatry of older people at University College London and a co-author of the report.
The incidence of dementia in Europe and North America has fallen by around 15 per cent per decade for the past 30 years. This has been attributed to lifestyle changes such as a reduction in smoking – even though the numbers of people with dementia are rising as people live longer.
The researchers say that the impact of lifestyle interventions is likely to be greatest among the most deprived individuals and in low- and middle-income countries.
‘Dementia is potentially preventable – you can do things to reduce your risk of dementia, whatever stage of life you are at.’