Could Viagra Lower Your Risk for Alzheimer’s Disease?

A study conducted in the U.K. and reported by TIME Magazine offers evidence that the erectile dysfunction (ED) drug Viagra (generic name: sildenafil) may help lower risk of Alzheimer’s disease. As one of a group of drugs known as phosphodiesterase Type 5 inhibitors, Viagra works by relaxing blood vessels and increasing blood flow in the penis. In a study published in Neurology, researchers found that these types of drugs were also associated with a lower risk of Alzheimer’s. The study analyzed the health records of nearly 270,000 men in the U.K. who were diagnosed with erectile dysfunction from 2000 to 2017. The researchers compared rates of Alzheimer’s disease among men who had been prescribed sildenafil to those among men who had not been prescribed the drug. Men who were prescribed the medication had an 18% lower risk of having Alzheimer’s than those who were not. The reduction was greater among men who got 20 or more prescriptions over the study’s five-year follow up period. “We didn’t have strong expectations [but] we definitely found a protective effect,” said the senior author of the study paper.

Two earlier studies, both conducted in the U.S., reached conflicting conclusions: one found a 69% lower Alzheimer’s risk among ED drug users while the other found no correlation. But there were said to be “confounding factors” affecting the latter study, and after controlling for those factors the connection between the drugs and a lower risk of Alzheimer’s remained. Speculation focuses on the possibility that because ED drugs work by relaxing the blood vessels and increasing blood flow, that effect may extend to the brain, where improved circulation could help to clear the buildup of toxic proteins linked to Alzheimer’s disease. Animal studies have also shown that the drugs indirectly increase levels of a brain chemical called acetylcholine, which is involved in memory, learning, and attention. One additional correlation is that the studies found the ED drugs had a stronger protective effect among men 70 years or older compared to men under 70. So the drugs appear to have a greater benefit among individuals at the greatest risk of Alzheimer’s.

So far only correlation, but not causality, has been documented. One limitation of the study is that the scientists only had data on the number of prescriptions the men received, and could not verify if they filled the prescriptions or used the medications properly. They could also not account for how much physical or sexual activity the men were doing. It’s possible that men using erectile dysfunction meds are more sexually and physically active than other men, which might be a causative factor. The senior author on the U.K. study said he hopes that other researchers will further explore the potential of ED drugs by conducting trials to address these issues by including men without erectile dysfunction, and also by including women in studies. He suggests that if the connection remains strong, these drugs could potentially provide another way for people to protect themselves from Alzheimer’s and its neurodegenerative manifestations.

Could Alzheimer’s Disease Be “Transmissible”?

The short answer is that it’s possible but highly unlikely and would occur only in the rarest of circumstances. But as reported by AARP, British researchers have found evidence of the possibility. In a report published in the journal Nature Medicine, the researchers identified five individuals who developed symptoms of Alzheimer’s before age 55 after having been treated in their youth with human growth hormone extracted from cadavers. The researchers speculate that a plausible explanation for the early onset dementia was that the human growth hormone the people were given contained amyloid beta proteins, which caused plaque deposits to develop in their brains. These amyloid plaques are considered a key component of the disease. The researchers were quoted as saying, “The clinical syndrome developed by these individuals can, therefore, be termed iatrogenic [medically induced] Alzheimer’s disease, and Alzheimer’s disease should now be recognized as a potentially transmissible disorder.”

It is important to note that cadaver-extracted growth hormone is no longer a procedure that’s used. Researchers emphasized that cadavers haven’t been the source of growth hormone for decades. It’s now created synthetically. Equally important, even if the association with growth hormone did lead to developing early Alzheimer’s, it in no way means the disease is “contagious.” Because “transmissible” does not mean “contagious,” as in being able to be acquired through ordinary contact. “There is no risk that the disease can be spread between individuals or in routine medical care,” read one expert’s statement.

AARP went on to say that from 1963 to 1985, about 7,700 children in the U.S. were given growth hormones extracted from cadavers. The Food and Drug Administration (FDA) suspended this use in 1985, after finding that four young adults likely contracted Creutzfeldt-Jakob Disease (CJD), a fatal brain disorder, from treatments they received two decades earlier. CJD also involves clumps of misformed amyloid proteins.

If there is any “plus” to this finding, it is that the possible connection between human growth hormone and Alzheimer’s disease may offer new avenues of research into cures and treatments for the disease. The lead author of the research said if Alzheimer’s and some other neurological conditions share similar disease processes to CJD, “this may have important implications for understanding and treating Alzheimer’s in the future.”