A recent study has found a potential link between taking erectile dysfunction medication, such as Viagra, and a reduced risk of developing Alzheimer’s disease. The study showed that men who were prescribed Viagra were 18% less likely to develop the most common form of dementia compared to those who did not take the medication. The risk reduction was even greater in men who had received 21 to 50 prescriptions of the medication, with a 44% lower risk of Alzheimer’s. However, it is important to note that this was an observational study and cannot confirm whether the medication actually protects against Alzheimer’s or if those who are less prone to the condition are simply more likely to take the medication.
“We can’t say that the drugs are responsible, but this does give us food for thought on how we move into the future,” said the lead author Dr Ruth Brauer at University College London. “We now need a proper clinical trial to look at the effects of these drugs on Alzheimer’s in women as well as men.”
Brauer and her team studied the medical records of over 260,000 men who were diagnosed with erectile dysfunction but had no signs of memory or cognitive issues. Of these men, slightly more than half were taking medications known as PDE5 inhibitors, which include sildenafil (sold as Viagra), avanafil, vardenafil, and tadalafil. The study followed the men for an average of five years, during which any new cases of Alzheimer’s disease were recorded.
Around the world, an estimated 55 million people are living with dementia, which is mostly caused by Alzheimer’s disease. There are new drugs that can clear abnormal proteins from the brain, and they have shown promise in slowing down the progression of the disease. However, the effects of these medicines seem to be only marginally effective.
The drug called Viagra was initially created to manage angina and high blood pressure. However, during a trial in Merthyr Tydfil involving Welsh miners, they noticed that the medication had an unexpected effect during the night. This led to the drug becoming a popular erectile dysfunction pill, generating billions of dollars.
Veins and arteries are relaxed by PDE5 inhibitors, which results in improved blood flow. This improved blood flow in the brain has been shown to protect against Alzheimer’s in animal studies. Additionally, PDE5 inhibitors have been found to increase levels of the cGMP compound, which may also help safeguard brain cells. PDE5Is may reduce Alzheimer’s disease risk in animals, but evidence in humans is inconclusive.
The journal Neurology published the findings, but there are other potential explanations for them. The researchers were unable to account for varying levels of physical and sexual activity among the men due to unreliable medical record-keeping. It is possible that the most physically and sexually active men, who were already at a low risk for Alzheimer’s, were also the most likely to use Viagra or similar medication.
Previous studies have produced conflicting results concerning the effects of Viagra on Alzheimer’s. In 2021, researchers at the Cleveland Clinic in Ohio reported a 69% decrease in the risk of Alzheimer’s among Viagra users, while a 2021 study at Harvard found no protective effect in patients with pulmonary hypertension.
If PDE5 inhibitors do protect against Alzheimer’s, the drugs would be expected to work in women as well as men. “We think it would be very worthwhile to run a trial in a wide group of people,” Brauer said.
“This is a significant development, as repurposing existing drugs for the prevention of dementia is a promising strategy to stop dementia from developing in the first place,” said Dr Ivan Koychev, a senior clinical researcher at the University of Oxford.
Developing drugs for Alzheimer’s disease is a costly and time-consuming process, according to Dr. Leah Mursaleen, who is the head of research at Alzheimer’s Research UK. She also warned that conducting a blinded placebo-controlled trial – in which neither doctors nor patients know who receives which medication – would be difficult due to the significant effects of the drugs.
“Being able to repurpose drugs already licensed for other health conditions could help accelerate progress and open up new avenues to prevent or treat dementia-causing diseases,” she added.
Dr Madhav Thambisetty, who is a senior investigator at the US National Institute on Aging, conducted a study in 2021, which revealed that Viagra did not offer any protective benefits. He expressed concerns that unmeasured factors such as sleep quality or diabetes management may lead to inaccurate findings. Moreover, he raised doubts about the plausibility of sildenafil, a drug that is only used by patients with erectile dysfunction when necessary, having the ability to alter the course of a chronic and progressive neurodegenerative disease.
“Although sildenafil can reach the brain through the bloodstream, it is important to consider whether its levels in the brain can be maintained at sufficiently high concentrations for a prolonged period of time. This may be necessary to alter the course of Alzheimer’s disease,” he stated. “This question is particularly relevant when comparing drugs like sildenafil, which are used only as needed, to drugs that are taken daily or multiple times a day over an extended period.”
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References:
1. Adesuyan, M., Jani, Y. H., Alsugeir, D., Howard, R., Ju, C., Wei, L., & Brauer, R. (2024). Phosphodiesterase Type 5 Inhibitors in Men With Erectile Dysfunction and the Risk of Alzheimer Disease: A Cohort Study. Neurology, 102(4), e209131.
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