The most accurate way yet of identifying who will get dementia has been developed by scientists from the University of Oxford.

Researchers say the new dementia risk score "strongly predicts" the chances of people over the age of 50 developing the debilitating disease within 14 years.

And they say that having diabetes, depression and high blood pressure can triple the risk of developing the condition.

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The system draws on 11 mostly modifiable risk factors to identify people most at risk from middle age onwards.

Up to 50 million people worldwide are thought to be living with dementia, with the number projected to triple by 2050.

But scientists say targeting key risk factors, several of which involve lifestyle, could potentially avert around 40 per cent of cases.

Several risk scores have been devised to try and predict a person’s chances of developing dementia while preventive measures are still possible.

But those scores have proved unreliable, and some rely on expensive and invasive tests, precluding their use in primary care.

To try and get round those issues, the Oxford team drew on two large groups of 50 to 73-year olds participating in two long term studiesUK Biobank study and Whitehall II study.

The research team compiled a list of 28 established factors associated with a higher or reduced risk of developing dementia, to which they applied a statistical method designed to identify and discard the least relevant factors.

That produced 11 predictive factors for any type of dementia: the UK Biobank Dementia Risk Score (UKBDRS).

The 11 factors were: age; education; history of diabetes; history of/current depression; history of stroke; parental dementia; economic disadvantage, high blood pressure; high cholesterol; living alone; and being a man.

The APOE gene, which is involved in the production of a protein that helps carry cholesterol and other types of fat in the bloodstream, is a known risk factor for dementia.

Its carriage was known for 157,090 participants in the UK Biobank study and 2,315 of those in the Whitehall II study and added to the risk score (UKBDRS-APOE).

Within 14 years, nearly two per cent of people in the UK Biobank group and just over three per cent of participants in the Whitehall II group developed dementia.

The predictive values of UKBDRS with and without APOE were compared with that of age alone; and the three other widely used risk scores.

UKBDRS-APOE produced the highest predictive score.

The researchers suggest that the accuracy of their risk score could be further improved by adding cognitive tests, a brain scan, and a blood test for indicators of neurodegeneration.

Lead author Dr Raihaan Patel said: "The UKBDRS may best be used as an initial screening tool to stratify people into risk groups, and those identified as high risk could then benefit from the more time intensive follow-up assessments described above for more detailed characterisation."