PARIS • Up to 40 per cent of dementia cases could be prevented or delayed, according to a report published last Thursday, which called for urgent action on risk factors from excessive drinking to air pollution.
The number of people around the world living with dementia is expected to soar from around 50 million today to more than 150 million by 2050.
But experts in a commission for the journal The Lancet said a range of policy actions could dramatically reduce or delay cases, in updated research based on analysis of a wide variety of international studies.
The report said a lack of education in childhood, mid-life hearing loss and smoking in older age accounted for 7 per cent, 8 per cent and 5 per cent of dementia cases respectively.
It also identified three new risks - head injuries and excessive alcohol consumption in middle age and exposure to air pollution later in life - which together are associated with 6 per cent of all cases.
"Our report shows that it is within the power of policymakers 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," said lead author Gill Livingston of University College London.
The study's recommendations included healthy lifestyles, policies to tackle pollution and prevent head injuries in high-risk occupations, and initiatives such as providing hearing aids.
Dementia is caused when the brain is damaged by diseases such as Alzheimer's or stroke. It can affect people's memory, moods and their ability to perform daily tasks.
Beyond the challenges it poses to individuals and families, experts estimate its economic cost at about US$1 trillion (S$1.4 trillion) a year.
The number of people living with dementia has surged as the global population expands and people live longer. Some two-thirds of people with dementia are now living in low-and middle-income countries.
The authors said tackling risk factors in these nations and among deprived communities in richer countries would have the greatest impact.
But co-author Adesola Ogunniyi, of the University of Ibadan in Nigeria, called for more research in these societies, with nearly all the evidence for dementia currently from studies in high-income countries.
Other factors identified in the report were hypertension (2 per cent) in mid-life, obesity in middle age (1 per cent), depression (4 per cent), social isolation (4 per cent), physical inactivity (2 per cent) and diabetes (1 per cent).
Responding to the study, Professor Tara Spires-Jones, of the UK Dementia Research Institute at the University of Edinburgh, said it provided an important set of practical measures that people can take to reduce their risk of dementia.
But she noted that the study suggested 60 per cent of cases "are, to the best of our knowledge, caused by things people cannot control, like their genes, so I hope this report will not lead to people feeling like having dementia is their 'fault'".
She cautioned that the data used "does not prove causation", adding there was evidence that brain changes in early dementia cause depression.