Men prescribed erectile dysfunction drugs were 18% less likely to go on to develop Alzheimer's disease than men who were not, according to research from University College London published in the online issue of the journal Neurology. The five-year study drew on the medical records of nearly 270,000 men with erectile dysfunction, and the association was strongest among those issued the most prescriptions during the study period.
The drugs in question, known as PDE5 inhibitors and sold under brand names including Viagra, widen blood vessels to increase blood flow. They were originally developed as treatments for high blood pressure, and the new findings have prompted the researchers to call for further work on whether the same compounds might have a role in preventing Alzheimer's, the most common cause of dementia.
The appeal of a result like this lies in the shortcut it might offer. As Dr Leah Mursaleen, Head of Research at Alzheimer's Research UK, points out, developing a new drug for a disease like Alzheimer's is expensive and can take many years, so finding a new use for a medicine already licensed for another condition could speed up progress and open fresh routes to preventing or treating the diseases that cause dementia.
The study has clear limits. It tracked prescriptions, not consumption, so the researchers had no way of knowing whether the men actually took the drugs they were given. An association found in medical records also cannot establish that the drugs were responsible for the lower rate of Alzheimer's diagnoses. Confirming or ruling out a genuine protective effect would require dedicated trials.