Viagra could be an effective treatment for Alzheimer’s disease, as per a study conducted in the United States. Hundreds of millions of people worldwide are affected by Alzheimer’s disease, the most common form of age-related dementia. Despite the growing number of cases, there is currently no effective treatment available. 

Researchers at the Cleveland Clinic used a large gene-mapping network to combine genetic and other data to determine which of the more than 1,600 FDA-approved drugs could be an effective treatment for Alzheimer’s disease. They gave drugs that target both amyloid and tau – two hallmarks of Alzheimer’s disease – higher scores than drugs that only target one of the two. 

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“Sildenafil, which has been shown to significantly improve cognition and memory in preclinical models, presented as the best drug candidate,” Dr Feixiong Cheng, the study lead told The Guardian. Viagra is the brand name of sildenafil.

Researchers then compared sildenafil users to non-users in a database of claims from more than 7 million people in the United States to look into the link between sildenafil and Alzheimer’s disease outcomes. 

After six years of follow-up, they discovered that sildenafil users were 69% less likely than non-sildenafil users to develop Alzheimer’s disease. To learn more about sildenafil’s potential role in Alzheimer’s disease, scientists created a lab model that demonstrated the drug increased brain cell growth and targeted tau proteins, providing insight into how it might effect disease-related brain changes. The research was published in the journal Nature Aging.

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The study does not prove a causal link between sildenafil and Alzheimer’s disease, according to Cheng. To determine sildenafil’s efficacy, he said, randomised clinical trials involving both sexes with a placebo control were required.

Dr Ivan Koychev, a senior clinical researcher at the University of Oxford, who was not involved in the study, told the Guardiam it was “an exciting development” because “it points to a specific drug which may offer a new approach to treating the condition”.

There are several important limitations to consider, according to Prof Tara Spires-Jones, deputy director of the University of Edinburgh’s Centre for Discovery Brain Sciences. “While these data are interesting scientifically, based on this study, I would not rush out to start taking sildenafil as a prevention for Alzheimer’s disease.”

Dr Susan Kohlhaas, director of research at Alzheimer’s Research UK, said, “Being able to repurpose a drug already licensed for other health conditions could help speed up the drug discovery process and bring about life-changing dementia treatments sooner. “

“Importantly, this research doesn’t prove that sildenafil is responsible for reducing dementia risk, or that it slows or stops the disease. The only way to test this would be in a large-scale clinical trial measuring sildenafil effect against the usual standard of care.”