Reducing 12 risk factors could delay or prevent 40 per cent of dementia cases, a leading study suggests.
The research, published in the prestigious Lancet medical journal, discovered three new risk factors for dementia, along with the nine listed in a 2017 paper.
The three new factors were excessive alcohol intake, head injury in mid-life and exposure to air pollution in later life, which together were associated with 6 per cent of all dementia cases.
An estimated 3 per cent of cases were attributable to head injuries in mid-life, 1 per cent of cases to high alcohol consumption (more than 21 units a week) in mid-life, and 2 per cent to air pollution in later life.
The remaining risk factors were associated with 34 per cent of all dementia cases.
The factors associated with the greatest proportion of dementia cases were less education in early life, hearing loss in middle age and smoking in later life (7, 8 and 5 per cent, respectively).
About 50 million people live with dementia globally, and this is projected to increase to 152 million by 2050, particularly in low-income and middle-income countries where about two thirds of all people with dementia live.
The neurodegenerative illness affects people, their families and the economy, at an estimated global cost of about $1 trillion (Dh3.67trn) a year.
But in certain countries the proportion of older people with dementia has fallen.
This is thought to be caused by improvements in education, nutrition, health care and lifestyle changes, demonstrating the possibility of reducing dementia through prevention.
The new report, published by 28 leading dementia academics, laid out a set of policies and lifestyle changes to help prevent the condition.
“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 Professor Gill Livingston of University College London.
“Interventions are likely to have the biggest impact on those who are disproportionately affected by dementia risk factors, like those in low and middle-income countries and vulnerable populations, including black, Asian and minority ethnic communities.
“As societies, we need to think beyond promoting good health to prevent dementia, and begin tackling inequalities to improve the circumstances in which people live their lives.
"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.
The report highlighted nine recommendations to help reduce the risk of dementia, including primary and secondary education for all children, decreasing harmful alcohol drinking, preventing head injuries, using hearing aids, protecting ears from damagingly loud noise and drastically improving air quality.
Based on the nine risk factors, scientists believe the potential to prevent cases of dementia is high.
While globally the original nine risk factors were estimated to contribute to 35 per cent of all dementia cases, in developing regions that number was higher: in China they might account for 40 per cent of cases, 41 per cent in India and 56 per cent in Latin America.
“In this context, national policies addressing dementia risk factors, like primary and secondary education for all and stopping smoking policies, might have the potential for large reductions in dementia and should be prioritised,” said the report's co-author Professor Adesola Ogunniyi of the University of Ibadan in Nigeria.
“We also need more dementia research coming from low and middle-income countries so we can better understand the risks particular to these settings.”
The study authors said that dementia sufferers were also at higher risk from Covid-19 than the general population because of their age and pre-existing illnesses such as hypertension.
Physical distancing can also be challenging for dementia patients, who may find it difficult to adhere to, or not understand, the guidelines.