Viagra may help prevent dementia by increasing blood flow in the brain

Sildenafil—better known as Viagra—may reduce the risk of vascular dementia, according to a recent study published in Circulation Research.

After participants took the drug for three weeks, scientists recorded positive changes in the behavior of blood vessels in the brain.

The study, called the OxHARP trial, lays the groundwork for future clinical trials.

Expanding Use of Viagra

Viagra, originally developed to treat angina, became known in the late 1990s as an effective treatment for erectile dysfunction.

Because it is a relatively safe drug and affects many organs such as the heart, liver, kidneys and brain, it is a good candidate for re-use.

For example, scientists have already investigated whether sildenafil can help treat conditions such as chronic pain, cancer, depression, kidney disease, and others.

The latest study looks at whether Viagra can help reduce the risk of developing vascular dementia.

What is vascular dementia?

Vascular dementia is a form of dementia caused by disruption of blood flow or damage to blood vessels in the brain. It often occurs after a stroke. The second most common form of dementia after Alzheimer's disease, vascular dementia accounts for 15-20% of dementia cases in North America and Europe.

Jose Morales, MD, a neurologist and neurointerventional surgeon at the Pacific Neuroscience Institute in Santa Monica, California, who was not involved in the new study, said there are "treatments that can help manage symptoms and slow the progression of the disease." However, "there is no cure," so identifying risk factors and ways to reduce them is important.

Cerebral microvascular disease (CSVD) is one such risk factor. CSVD is an umbrella term for a number of conditions that affect the small blood vessels in the brain.

Alastair Webb, a consultant neurologist at Imperial College London in the UK, provided an overview of CSVD:

"Microvascular disease is chronic damage to the small blood vessels deep inside the brain, causing them to become narrow, blocked and leaky. This damage occurs to some degree in most people as they age, but in some it is more severe, often due to long-term high blood pressure."

"The resulting damage can further reduce blood flow to deep parts of the brain, leading to strokes and dementia," he explained.

How Viagra May Affect Blood Vessels in the Brain

In a recent study, researchers recruited 75 people with neurological signs of CSVD.

Each participant received three-week courses of sildenafil, placebo, and cilostazol, a vascular disease treatment. Each course of medication was separated by a washout period of at least one week.

Testing all three drugs on all participants is called a crossover trial. These studies are powerful because each participant acts as their own control. They also require fewer participants to achieve statistically significant results.

The researchers focused on the following indicators.

• Cerebral pulsatility: Webb described this as "stronger pulsations of blood flow to the brain with each heartbeat."
• Cerebrovascular reactivity: This is "decreased reactivity of the blood vessels in the brain," according to Webb.
• Cerebrovascular resistance: how much resistance there is to blood flow in the vessels.
• Cerebral blood flow: Blood supply to the brain.

Why scientists decided to study sildenafil:

Webb responded: "It causes vasodilation, increasing blood flow and blood vessel reactivity," he said. "So it had the right type of action to improve the blood flow problems seen in our patients, but it was unclear whether it worked in the brain in the same way."

Fewer side effects compared to drugs for poor circulation

The researchers found that sildenafil did not improve cerebral pulsatility compared with placebo. Although Webb "had reason to believe that it would reduce pulsations," the team was not entirely surprised that it did not work that way.

However, sildenafil improved cerebrovascular reactivity and resistance, as well as cerebral blood flow compared with placebo.

Compared to cilostazol, Viagra showed similar results but caused fewer side effects such as diarrhea.

The authors concluded:

"Overall, the improvement of cerebrovascular dynamics with sildenafil provides a new potential therapy for preventing [cerebral microvascular disease] progression that should be tested in clinical trials."

While this is just a start, it is a step toward understanding how to reduce the risk of vascular dementia.

Why Use Viagra to Reduce the Risk of Dementia?

On why Viagra may help reduce the risk of vascular dementia, Rakesh K. Kukreja, a professor of internal medicine at the University of Virginia School of Medicine in Richmond, who was not involved in the study, said:

"Sildenafil is a potent inhibitor of the enzyme phosphodiesterase 5 (PDE5), which breaks down the powerful vasodilator molecule cyclic guanosine monophosphate (cGMP)."

"By preventing the breakdown of cGMP, sildenafil promotes relaxation of blood vessels and improves blood flow. Thus, the increased cerebral blood flow and reduced vascular resistance from sildenafil treatment may impact the risk of dementia," he said.

It is worth mentioning that the results of this study are consistent with earlier studies.

For example, a study in a rodent model of vascular dementia found that Viagra improved cognitive ability and memory. Other rodent studies have found similar results.

In addition, studies in human populations have concluded that Viagra use is associated with a reduced risk of developing Alzheimer's disease. Similarly, Kukreja described another study involving "insurance claims data for 7.23 million people."

In that study, he explained, "sildenafil use was associated with a 69% reduction in the risk of developing Alzheimer's disease."

Addressing lifestyle risk factors for dementia

While more research is needed on Viagra and vascular dementia, there are lifestyle factors that may reduce a person's risk.

Dr Tim Beanland, head of knowledge at the Alzheimer's Society, who was not involved in the study, described some lifestyle factors that increase the risk of vascular dementia:

"We know that what's good for the heart is good for the brain, so a healthy diet and lifestyle, including not smoking or drinking large amounts of alcohol, can help reduce the risk of dementia and other conditions such as heart disease, stroke, diabetes and some cancers."

For people already living with dementia, he said there is "growing evidence that regular exercise, looking after your health and staying mentally and socially active can help reduce the progression of dementia symptoms."

It's Too Early to Use Viagra to Prevent Dementia

The results of this study suggest that sildenafil may help reduce the risk of vascular dementia in people with CSVD. However, it measured changes in aspects of cerebral blood flow over a relatively short period of time.

To get a clearer picture of whether Viagra and similar drugs can actually reduce risk, scientists will need to follow people for many years to assess whether their risk is actually reduced.

Webb plans to continue this line of research:

"It is very important to continue this work. We need to do more research to determine the best dose of the drug and the best drug in this group to use further," he said.

"We're looking to test it in a much larger study to see not only whether it improves blood flow to the brain, but whether it reduces the risk of stroke and dementia," he added.