The erectile dysfunction drug Viagra may be linked to a lower risk of Alzheimer’s disease, according to a new study.

Researchers found that using Viagra (also called sildenafil) was associated with a 69% reduced risk of Alzheimer’s disease, when accounting for other factors like sex, race and age.

Experts from Cleveland in the US analysed insurance claims data from more than seven million people and used computer modelling to look for drugs that might target areas in dementia.

They found that men on Viagra had a substantially lower risk of Alzheimer’s disease, and called for more research into its potential use.

Alzheimer’s disease (AD) is the most common form of age-related dementia, affecting hundreds of millions of people worldwide, and there  is currently no effective treatment.

The authors of the new study said they cannot definitely say there is a causal relationship between Viagra and Alzheimer’s, but called for this to be tested in a clinical trial.

Lead investigator Dr Feixiong Cheng, from the Cleveland Clinic, said the findings were encouraging but said more work was needed.

“Because our findings only establish an association between sildenafil use and reduced incidence of Alzheimer’s disease, we are now planning a mechanistic trial and a phase II randomised clinical trial to test causality and confirm sildenafil’s clinical benefits for Alzheimer’s patients,” he said.

Viagra was originally designed as a heart drug but doctors also found it  improved blood flow to the penis.

At least two-thirds of men have improved erections after taking it, according to the NHS.