One in three cases of dementia could be prevented if more people looked after their brain health throughout life, according to an international study in the Lancet.
It lists nine key risk factors including lack of education, hearing loss, smoking and physical inactivity.
The study is being presented at the Alzheimer’s Association International Conference in London.
By 2050, 131 million people could be living with dementia globally.
There are estimated to be 47 million people with the condition at the moment.
Nine factors that contribute to the risk of dementia
These risk factors – which are described as potentially modifiable – add up to 35%. The other 65% of dementia risk is thought to be potentially non-modifiable.
Not smoking, doing exercise, keeping a healthy weight, treating high blood pressure and diabetes can all reduce the risk of dementia, as well as cardiovascular disease, and cancer.