published in the journal Nature Aging.
Patients who used the drug sildenafil, the generic name for Viagra, were 69% less likely to develop the disease than were nonusers.
“Sildenafil, which has been shown to significantly improve cognition and memory in preclinical models, presented as the best drug candidate,” Feixiong Cheng, PhD, the lead study author in the Cleveland Clinic’s Genomic Medicine Institute, said in a statement.
“Notably, we found that sildenafil use reduced the likelihood of Alzheimer’s in individuals with coronary artery disease, hypertension, and type 2 diabetes, all of which are comorbidities significantly associated with risk of the disease, as well as in those without,” he said.
Alzheimer’s, which is the most common form of age-related dementia, affects hundreds of millions of people worldwide. The disease is expected to affect nearly 14 million Americans by 2050. There is no approved treatment for it.
Dr. Cheng and colleagues at the Cleveland Clinic used a large gene-mapping network to analyze whether more than 1,600 Food and Drug Administration–approved drugs could work against Alzheimer’s. They gave higher scores to drugs that target both amyloid and tau proteins in the brain, which are two hallmarks of the disease. Sildenafil appeared at the top of the list.
Then the researchers used a database of health insurance claims for more than 7 million people in the U.S. to understand the relationship between sildenafil and Alzheimer’s disease outcomes. They compared sildenafil users to nonusers and found that those who used the drug were 69% less likely to have the neurodegenerative disease, even after 6 years of follow-up.
After that, the research team came up with a lab model that showed the sildenafil increased brain cell growth and targeted tau proteins. The lab model could indicate how the drug influences disease-related brain changes.
But Dr. Cheng cautioned against drawing strong conclusions. The study doesn’t demonstrate a causal relationship between sildenafil and Alzheimer’s disease. Researchers will need to conduct clinical trials with a placebo control to see how well the drug works.
Other researchers said the findings offer a new avenue for research but don’t yet provide solid answers.
“Being able to repurpose a drug already licensed for health conditions could help speed up the drug discovery process and bring about life-changing dementia treatments sooner,” Susan Kohlhaas, PhD, director of research at Alzheimer’s Research UK, told the Science Media Centre.
“Importantly, this research doesn’t prove that sildenafil is responsible for reducing dementia risk, or that it slows or stops the disease,” she continued. “If you want to discuss any treatments you are receiving, the first port of call is to speak to your doctor.”
And doctors won’t likely recommend it as a treatment just yet either.
“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,” Tara Spires-Jones, PhD, deputy director of the Centre for Discovery Brain Sciences at the University of Edinburgh, told the Science Media Centre.
A version of this article first appeared on WebMD.com.