Viagra can reduce the risk of Alzheimer's disease by almost a fifth, according to study of 250,000 impotent men

Viagra and other impotence pills can brighten the brain and reduce the risk of Alzheimer's disease by as much as 18 percent, a study shows.

Men who took the little blue pills for erectile dysfunction had increased brain activity and were less likely to develop dementia later in life.

Researchers found that the drugs, originally developed to treat high blood pressure, can enter the brain and activate cell signals closely linked to memory.

Dr. Leah Mursaleen, head of research at Alzheimer's Research UK, said: 'Developing drugs for diseases such as Alzheimer's is a costly process and can take many years.

'Being able to repurpose already licensed drugs for other health conditions could accelerate progress and open new avenues to prevent or treat dementia-causing diseases.'

The study, published in the journal Neurology, looked at 269,725 men with an average age of 59 who were diagnosed with erectile dysfunction but had no memory or thinking problems.

Over five years, among those not taking Viagra or similar drugs, 9.7 in 10,000 were diagnosed with Alzheimer's disease, compared with 8.1 in 10,000 among those who did take the pills.

Those who took more pills appeared to have a correspondingly lower risk of contracting Alzheimer's disease.

After adjusting for other risk factors, including smoking, diet and alcohol consumption, the pills were linked to an 18 percent reduced risk.

Researcher Matthew Adesuyan from University College London said: 'The results are encouraging and could point to a new way to reduce the risk of Alzheimer's.'

Dr. Ruth Brauer added: 'While we are making progress with new treatments for Alzheimer's disease that clear amyloid plaques in the brain, we urgently need treatments that can prevent or slow the development of Alzheimer's disease.

'More research is needed to confirm these findings, learn more about the potential benefits and mechanisms of these drugs and look at the optimal dosage.

'A randomized, controlled trial with both male and female participants is warranted to determine whether these findings would also apply to women.'

Tara Spires-Jones, chair of the British Neuroscience Association, said: 'This study does not conclusively prove that erectile dysfunction drugs reduce the risk of Alzheimer's, but provides good evidence that these types of drugs are worth further investigation in the future.'

In addition to helping men perform in the bedroom, Viagra – also known as Sildenafil – has been shown to have several other benefits. Last year, a study found that it can help kill tumors of the lungs, prostate, stomach and ovaries.