Viagra improves blood flow to the brain and could help prevent dementia, a new study by the University of Oxford suggests.

The university researchers found that the drug, also called sildenafil, enhances the function of brain blood vessels in patients at increased risk of the condition.

Experts suggest the research may have the potential to transform the treatment and prevention of vascular dementia, caused by reduced blood flow to the brain, which currently lacks specific therapies.

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The study, published in Circulation Research, involved 75 people who had experienced a minor stroke and showed signs of mild to moderate small vessel disease.

Everyone received Viagra – commonly used to treat erectile dysfunction – a placebo, and cilostazol (a similar drug) over three-week periods in a random order.

The researchers found that Viagra increased blood flow in both large and small brain vessels, and both Viagra and cilostazol lowered blood vessel resistance in the brain.

Additionally, Viagra caused fewer side effects compared with cilostazol, particularly with less incidence of diarrhoea.

Dr Alastair Webb, associate professor at the Wolfson Centre for Prevention of Stroke and Dementia at Oxford, said: “This is the first trial to show that sildenafil gets into the blood vessels in the brain in people with this condition, improving blood flow and how responsive these blood vessels are.

“These two key factors are associated with chronic damage to the small blood vessels in the brain, which is the commonest cause of vascular dementia."

The researchers say further larger trials are needed to confirm these findings and explore sildenafil’s potential in preventing vascular dementia on a broader scale.