Untreated vision loss and bad cholesterol have been cited in new research as high risk factors for dementia, according to a Lancet Commission study, part-funded by the Alzheimer’s Society.

The updated Lancet Commission study on dementia prevention, completed this summer, added untreated vision loss in later life and high low-density lipoprotein cholesterol (bad cholesterol) in mid-life as risk factors for developing the illness. They contribute to 2 per cent and 7 per cent of cases respectively. The report says that eliminating all of the addressable risk factors could theoretically halve the number of dementia cases.

As well as having far reaching benefits for so many individuals – the number of people living with dementia is forecast to triple to almost 153 million by 2050 – addressing the risk factors and reducing the number of people living with the illness would bring down the global costs linked to dementia, which now exceed £780 billion a year.

Fiona Carragher, chief policy and research officer at Alzheimer’s Society says: “Dementia is the UK’s biggest killer and a global crisis affecting more than 55 million people, but it’s never too early or too late to reduce your dementia risk. Some dementia risk factors, such as alcohol consumption and lack of physical exercise can be managed by changing your lifestyle.

“This Lancet Commission study suggests that nearly half of dementia cases around the world could be delayed or prevented. If we can support people to reduce their dementia risk and address the societal change needed, this could mean potentially hundreds of thousands fewer people in the UK will go on to develop dementia.”

Some of the highest risk factors cannot be changed. Age is the biggest one, with the over 75s most at risk. There is also a genetic risk and currently more women than men live with dementia in the UK. This could be because women live longer, and it might be impacted by women who are currently over 80 having had less opportunities for education and work when they were younger.

Some of the risk factors need to be addressed on a societal level, including social isolation, education inequalities and air pollution. People who live in deprived areas are at a higher risk, which might be because of the lack of opportunities to keep them mentally active; less access to health and social care and higher levels of air pollution. Small particles from traffic fumes and burning wood in the home have been identified as risk factors.

Access to good health care is important to help with other risk factors including hearing and vision loss and head injuries. The Lancet commission has made a number of recommendations including making hearing aids available for people with hearing loss, providing children with good-quality education, being cognitively active in midlife and detecting and treating high cholesterol from the age of 40.

The risk factors that are most controllable by the individual are taking more

exercise, stopping smoking and stopping excessive alcohol consumption. Tackling these lifestyle behaviours could give further resiliency against some of the other risk factors, including obesity, high blood pressure, high cholesterol, depression and diabetes.