Why Viagra has been linked with better brain health
Viagra can be a wonder drug for men with erectile dysfunction, helping them maintain their sex lives as they age. Now new research suggests the little blue pill may also be beneficial to aging brains.
The findings are based on a massive study of nearly 270,000 middle-aged men in Britain. Researchers at University College London used electronic medical records to track the health of the men, who were all 40 or older and had been diagnosed with erectile dysfunction between 2000 and 2017. Each man’s health and prescriptions were tracked for at least a year, although the median follow-up time was 5.1 years.
During the study, 1,119 men in the cohort were diagnosed with Alzheimer’s disease.
The researchers noticed a distinctive pattern. The men who were prescribed Viagra or a similar drug had an 18 percent lower risk of developing Alzheimer’s disease, compared with men who weren’t given the medication.
The researchers also found an even larger difference in men who appeared to use Viagra more often. Among the highest users, based on total prescriptions, the risk of being diagnosed with Alzheimer’s was 44 percent lower. (Men with erectile dysfunction are instructed to only take Viagra before sex, and no more than once a day.)
“I’m excited by the findings but more excited because I feel this could lead to further, high-quality studies in a disease area that needs more work,” said Ruth Brauer, a lecturer in pharmacoepidemiology at the University College London School of Pharmacy and the principal investigator of the study.
There’s a limit to how much we can conclude from the study results. The findings show an association between lower Alzheimer’s risk and Viagra use, but don’t prove cause and effect. For instance, it may be that Viagra use is a marker for better overall health, and that men who have more sex also are more physically active as well. Physical activity is independently associated with a lower risk of Alzheimer’s disease, Brauer said.
Sildenafil, the generic name for Viagra, was never supposed to be a sex drug. Pfizer had developed the drug as a cardiovascular medication to treat hypertension and chest pain called angina. The company had been conducting clinical trials using sildenafil as a heart medication when some patients reported an unexpected side-effect - erections.
Viagra is part of a class of drugs known as phosphodiesterase Type 5 Inhibitors, or PDE-5 drugs. The drugs work by dilating blood vessels and increasing blood flow throughout the body, including to the penis. Since its discovery as an erectile dysfunction treatment, sildenafil also has been used to treat pulmonary arterial hypertension for both men and women.
The link between heart health and sexual health is strong. Erectile dysfunction can be an early warning sign of coronary artery disease. And an unhealthy vascular system is one of the reasons men start having problems with erections.
Vascular risk factors have also been linked to certain types of dementia, including Alzheimer’s disease, so researchers have been intrigued about whether erectile dysfunction treatments can affect brain health as well.
Animal studies of PDE-5 inhibitors have shown the drug may help prevent cognitive impairment by, in part, increasing blood flow in the brain, but researchers who conducted a review of the available research say the efficacy of the class of drugs “remains unclear.” And Brauer said the findings in animals are only “possible mechanisms” in humans.
“There is an idea that if we can help with improving blood flow in the brain, maybe we can also reduce the risk for Alzheimer’s disease,” said Sevil Yasar, an associate professor of medicine at Johns Hopkins University and the co-author of an editorial that accompanied the study in Neurology.
Stanton Honig, a professor of urology at Yale School of Medicine, said the newest study is far from definitive. “You can’t draw any conclusions” from the study because “there are so many other factors” at play besides whether a man takes a pill for erectile dysfunction.
“Someone who is more likely to take a pill like that at 70, they’re probably more active, they’re more likely involved with their partners, things like that,” Honig said. “There’s too many confounding variables to make a definitive statement that it’s the pills or it’s the patients that are taking the pills that are less likely to be neurologically impaired.”
Brauer said the average “pack” per prescription is four tablets. But it’s not clear if the men took all the tablets prescribed and, if so, how often.
“We do not know if people used the prescribed drugs as intended nor could we measure sexual activity or physical activity levels,” Brauer said. “We need further studies to show if our results would hold up in a group of men without erectile dysfunction and - even better - it would be better to run our study in a group of men and women.”
Previous studies on different populations have come to somewhat contradictory conclusions. A Cleveland Clinic study found a significantly reduced risk of Alzheimer’s disease among those using sildenafil, said Feixiong Cheng, the director of the Cleveland Clinic Genome Center and the principal investigator of the study. But a study by researchers at Harvard Medical School and the National Institute on Aging found “no association” between the use of sildenafil, or other PDE-5 inhibitors, and the risk of Alzheimer’s disease, said Rishi Desai, an associate professor at Harvard Medical School.
Rebecca Edelmayer, the senior director of scientific engagement for the Alzheimer’s Association, said in an email that it remains unclear whether Viagra and similar drugs have an effect on Alzheimer’s risk. “Further research and specifically designed, randomized clinical trials are a necessary step,” she said.
For now, the findings don’t suggest that men should start taking Viagra if they don’t need it. But we do know that Viagra is an effective treatment for erectile dysfunction, and men who are experiencing the problem should see a doctor and discuss both their sexual health and cardiovascular health.
“You should not take Viagra to reduce your risk,” Yasar said. “You should eat healthy. You should exercise. There’s plenty of evidence for that.”
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