Scottish research, published in the journal Neurology, found that lower childhood intelligence increases the risk of vascular dementia, a disease which currently affects 112,000 people in the UK.
The results suggest that interventions to lower blood pressure and smoking targeted from early in life to those with a lower IQ could reduce the numbers of people developing dementia in old age. They also help scientists to understand what is happening in the brains of people with dementia and the best way to tackle different dementias.
Researchers based at the University of Edinburgh compared the records of 173 people who participated in the Scottish Mental Survey of 1932, when almost every child aged 11 years in Scotland took a mental ability test.
They showed that lower childhood IQ increased the risk of vascular dementia, but not Alzheimer's disease. Because the difference was not seen in Alzheimer's, this suggests that increased risk of "dementia" may be due to vascular causes.
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.
With 700,000 people in the UK with dementia today, we urgently need to fund more research to find ways to prevent, treat or cure dementia, but research is seriously under-funded."