Drugs commonly used to treat erectile dysfunction may reduce the risk of Alzheimer's disease, finds a new study led by UCL researchers.
The authors of the new Neurology paper found that men prescribed erectile dysfunction drugs were 18% less likely to develop Alzheimer's disease years later.
The study included 269,725 men who were diagnosed with erectile dysfunction and who did not have any memory or thinking problems at the start of the study. Just over half (55%) were taking phosphodiesterase type 5 inhibitor drugs, including sildenafil (sold as Viagra), tadalafil (Cialis), vardenafil and avanafil, and were compared to those with erectile dysfunction but not prescribed the drugs.
Erectile dysfunction drugs work by dilating blood vessels and were initially developed to treat hypertension and angina. They act on a cell signalling messenger that has also been investigated for its links to memory. These drugs are also able to cross the blood-brain barrier and may affect brain cell activity. Animal research has found phosphodiesterase type 5 inhibitors to have some neuroprotective benefits.
For the current study, based on prescription records, the researchers found that men who were prescribed erectile dysfunction drugs were 18% less likely to develop Alzheimer's disease later on (after the researchers adjusted the findings for potential confounding factors such as age, underlying health conditions, co-prescribed medications and smoking status), with an average follow-up time of 5.1 years. This association was strongest among men who had been issued the most prescriptions, suggesting that using the drug more regularly might have a greater impact on Alzheimer's risk.
Among the men prescribed erectile dysfunction drugs, 749 developed Alzheimer's disease, which corresponds to a rate of 8.1 cases per 10,000 person-years. Person-years represent both the number of people in the study and the amount of time each person spends in the study. Among the men who were not prescribed the drugs, 370 developed Alzheimer's disease, corresponding to 9.7 cases per 10,000 person-years.
Lead author Dr Ruth Brauer (UCL School of Pharmacy) said: "Although we're making progress with the new treatments for Alzheimer's disease that work to clear amyloid plaques in the brain for people with early stages of the disease, we desperately need treatments that can prevent or delay the development of Alzheimer's disease.
"More research is needed to confirm these findings, learn more about the potential benefits and mechanisms of these drugs and look into the optimal dosage. A randomised, controlled trial with both male and female participants is warranted to determine whether these findings would apply to women as well."
First author, PhD student Matthew Adesuyan (UCL School of Pharmacy) said: "While we cannot say based on our findings whether the drugs themselves were reducing people's risk of Alzheimer's disease, the results are encouraging and may point to a new way to reduce Alzheimer's risk."
