A study by Edinburgh University found lower childhood intelligence increases the risk of vascular dementia, a disease affecting 112,000 people in the UK.

The results also suggest that introducing measures early in life to lower blood pressure and discourage smoking could help those with a lower IQ reduce the risk of developing the brain illness in later life.

Researchers compared the records of 173 people who took part in the Scottish Mental Survey of 1932, a mental ability test taken by almost every child aged 11 in Scotland.

They found that lower childhood IQ increased the risk of vascular dementia.

The condition, the second most common form of dementia after Alzheimer's disease, is linked to high blood pressure, high cholesterol or smoking.

Lead researcher Dr Brian McGurn said: "Our work suggests a possible link between mental ability in early life and the risk of developing vascular dementia.

"The unique data available from the Scottish Mental Survey means the link can be demonstrated independently of factors like socio-economic status and education."

Rebecca Wood, chief executive of the Alzheimer's Research Trust, said: "This research confirms that vascular risk factors are very important in tackling dementia. If we live a healthier lifestyle and reduce our risk of high blood pressure, cholesterol and don't smoke, then this gives us a much better chance of avoiding dementia later in life."

The research, Childhood cognitive ability and risk of late-onset Alzheimer and vascular dementia, is published in the Neurology journal.