It was found that people who had taken blood pressure drugs, particularly a class known as beta blockers, showed fewer changes in the brain linked to Alzheimer’s disease.

Findings of a new study were presented at the American Academy of Neurology Annual Meeting in San Diego.

Researchers examined the brains of 774 men after they had died, 610 of whom had been treated for high blood pressure.

Around one in seven of those had been given only beta blockers, 18 per cent had received beta blockers and another drug and the others had been given different drugs.

It was found that the men who had received beta blockers as their only blood pressure medication had fewer abnormalities in their brains compared to those who had not been treated for their hypertension, or who had received other blood pressure medications.

Those who had been given beta-blockers in combination with other drugs also had fewer brain leisons and less shrinkage but not to the same extent at those who had used them alone.

In 2011, more than 30m prescriptions were dispensed for beta blockers in England, showing that millions of patients have used the drugs.

Lead researcher Dr Lon White, of the Pacific Health Research and Education Institute in Honolulu, said: “With the number of people with Alzheimer’s disease expected to grow significantly as our population ages, it is increasingly important to identify factors that could delay or prevent the disease.

“These results are exciting, especially since beta blockers are a common treatment for high blood pressure.”

Earlier research has shown that high blood pressure in middle age is a strong risk factor for dementia.

The number of people with dementia is expected to explode to 1.7m by 2050.

Dr Simon Ridley, head of research at Alzheimer’s Research UK, said: “Hypertension is a known risk factor for Alzheimer’s and other causes of dementia, and keeping high blood pressure in check could be important for preventing these diseases.

“This study suggests a link between the use of beta blockers and fewer signs of dementia, but as the results of this study have yet to be published in full, it’s not clear what caused this link. It’s important to note that this study only looked at Japanese-American men, and these results may not be applicable to the wider population.

“While we can’t conclude from this study that beta blockers can prevent dementia, a better understanding of the links between high blood pressure and dementia could be crucial for developing new treatments or approaches to prevention.

“With 820,000 people affected by dementia in the UK, and that number increasing, we urgently need to find ways to prevent the diseases that cause it – that requires a massive investment in research.”

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By Rebecca Smith, Medical Editor