Four in 10 dementia cases could be prevented or delayed with lifestyle changes, a major study has shown, with hearing loss found to be the biggest risk.
A report by the Lancet Commission on Dementia Prevention has identified 12 preventable factors which play a huge role in the onset of the condition.
The biggest modifiable risk factor was hearing loss, believed to be responsible for eight per cent of cases. Scientists now think hearing loss may trigger brain damage elsewhere and also stop people from socially interacting, which is known to protect the brain from cognitive decline.
Poor education in early years is also linked to seven per cent of cases, and smoking to five per cent.
Physical inactivity, obesity and drinking too much are responsible for four per cent of cases cumulatively, while depression and social isolation combined are to blame for eight per cent of cases. Diabetes and high blood pressure are responsible for the final two per cent.
Altogether, the 12 risk factors are responsible for 40 per cent of all cases, which amounts to around 340,000 cases in Britain.
There are currently no treatments for dementia, but policy changes to improve health and access to education could have a similar impact to drugs.
“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 (UCL).
“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 was authored by 28 of the world’s leading dementia experts, who reviewed the most up-to-date science on the risk factors. They are calling on governments to make important policy changes to help lower the number of people developing the condition.
They recommend health interventions to keep blood pressure low, and the encouragement of the use of hearing aids and protecting people from high noise.
Reducing air pollution and second-hand tobacco smoke and preventing head injuries by targeting high risk occupations and transport would also help bring down cases.
The authors also warn that people with dementia are particularly at risk from Covid-19 and are calling for people to be tested before entering care homes in order to protect existing residents.
Fiona Carragher, the director of research and influencing at the Alzheimer’s Society, which part-funded the Lancet Commission, said: “Dementia is a global crisis affecting more than 50 million people, leaving devastated families in its wake.
“The news that 40 per cent of dementia cases are, in theory, now preventable is certainly welcome, but stopping thousands of people from being stripped of their memories, relationships and identities will rely on more than just this knowledge alone.
“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.”
However, some experts said the new report might lead some people to think they were to blame for their dementia.
The biggest known risk for late-life dementia is genetic – specifically carriers of the Apolipoprotein E epsilon 4 genotype will see a four to 12-fold increase in the likelihood of experiencing dementia in their lifetime.
Professor Tara Spires-Jones, of the UK Dementia Research Institute at the University of Edinburgh, and deputy director of the university’s Centre for Discovery Brain Sciences, said: “This report estimates that 40 per cent of dementias might be preventable with lifestyle changes, which means that the remaining 60 per cent are, to the best of our knowledge, caused by things people can’t control, like their genes.
“So I hope that this report will not lead to people to feel that having dementia is their fault. It is important to use the data in this report to keep working to understand how lifestyle can make the brain more vulnerable or resilient to dementia so that we can develop life changing treatments for people living with dementia.”