Drugs used to treat erectile dysfunction may reduce the risk of Alzheimer’s disease, UK researchers have reported.

A study in Neurology of more than 269,000 men diagnosed with erectile dysfunction who did not have any memory problems at the start found that those prescribed phosphodiesterase type 5 (PDE5) inhibitor drugs were 18% less likely to develop Alzheimer’s disease later on.

The association, which was found through the analysis of medical records, was strongest among those who had been issued the most prescriptions for medicines which included sildenafil (Viagra), tadalafil (Cialis), vardenafil and avanafil.

There was a 44% lower risk of Alzheimer’s in those who received 21 to 50 prescriptions of the erectile dysfunction pills over the course of the study, the researchers said.

It suggests that using the drug more regularly might have a greater impact on Alzheimer’s risk, the team from University College London concluded.

In all 55% of the men in the study were taking Just over half (55%) were taking PDE5 inhibitor drugs, over the five-year follow up period.

The researchers took into account age, underlying health conditions, co-prescribed medications and smoking status.

Among those prescribed erectile dysfunction drugs, 749 developed Alzheimer’s disease at a rate of 8.1 cases per 10,000 person-years.

For those not prescribed them, 370 developed Alzheimer’s disease, equating to a rate of 9.7 cases per 10,000 person-years, the team reported.

Previous animal research has found PDE5 inhibitors to have some neuroprotective benefits, they noted. They also pointed out that this study was observational and could not account for differing levels of physical and sexual activity among the men.

Study lead Dr Ruth Brauer (UCL School of Pharmacy) said: ‘Although we’re making progress with the new treatments for Alzheimer’s disease that work to clear amyloid plaques in the brain for people with early stages of the disease, we desperately need treatments that can prevent or delay 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 into the optimal dosage.

‘A randomised, controlled trial with both male and female participants is warranted to determine whether these findings would apply to women as well.’

Dr Ivan Koychev, senior clinical researcher, Dementia Platform UK at the University of Oxford, said the study had identified that the reduced risk appeared to be dose-dependent.

‘It is also more pronounced in people with heart disease risk factors (high blood pressure, diabetes), suggesting that the effect may be due to neuroprotection through vascular mechanisms.’

But he noted that because PDE5 inhibitors are typically taken as needed it is difficult to know how much was actually taken and at what frequency.

‘Overall, this is a significant development as repurposing already existing drugs for the prevention of dementia is a promising strategy to stop dementia from developing in the first place using drugs with known safety profile.’

This article was first published by our sister title Pulse