ONE in three cases of dementia could be prevented by activities which improve brain health, a new study has found.

There are nine key risk factors, including lack of education, hearing loss, smoking and physical inactivity, which contribute to the development of dementia, the report revealed.

The study by Lancet 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.

According to the study, nine lifestyle factors that contribute to the risk of dementia are:

• Mid-life hearing loss - responsible for nine per cent of the risk

• Failing to complete secondary education - eight per cent

• Smoking - five per cent

• Failing to seek early treatment for depression - four per cent

• Physical inactivity - three per cent

• Social isolation - two per cent • High blood pressure - two per cent

• Obesity - one per cent

• Type 2 diabetes - one per cent

These risk factors add up to a 35 per cent increased change of developing dementia.

The other 65 per cent of dementia risk is beyond the individual's control, and includes a family history of the condition.