Research looking into the connection between herpes and dementia could lead to new antiviral drugs.
As evidence accumulates that herpes may increase the risk of developing dementia, researchers are beginning to move on to the next step:
Finding out whether drugs that fight herpes might keep dementia at bay.
Several studies from Taiwan published earlier this year cemented, for many researchers, a strong likelihood of a connection between herpes and dementia.
That raised the possibility of one day proving the connection and developing treatments around it.
Researchers have been already trying to pursue those next steps.
A new paper published last month summed up the recent findings from Taiwan and elsewhere.
But it also laid out a road map for future research toward the development of an antiviral drug that might one day help prevent dementia.
That prevention is a sort of holy grail right now. Experts estimate more than 10 percent of people between ages 65 and 74 and a quarter of people over 85 have dementia, of which Alzheimer’s is the most common form.
And those numbers are rising.
In the new review paper, author Ruth Itzhaki, PhD, writes that “even if the effects [of a treatment] were merely a delay in onset of the disease, this would still be enormously beneficial for patients, carers and the economy.”
Itzhaki, a neuroscience professor at the University of Manchester in England and a longtime proponent of the possibility of a herpes-dementia connection, told Healthline she’s currently pursuing funding to conduct clinical trials in the United Kingdom on antivirals that could be used against Alzheimer’s.
A similar clinical trial is already underway in the United States.
Researchers are giving people with Alzheimer’s who have tested positive for the herpes strains HSV-1 or HSV-2 the common anti-herpes drug valacyclovir. It’s available under the brand name Valtrex.
Essentially, they’re trying to repurpose a drug used for cold sores and chickenpox for a currently irreversible neurodegenerative disease.
But it might work. It just might take a while to find out.
It might work because the connection between the two conditions seems pretty strong, and there’s mounting evidence herpes may even be a cause of dementia.
Itzhaki says a causal relationship hasn’t yet been established by current research, but it’s been “strongly suggested.”
The Taiwanese studies concluded that herpes strains HSV-1, HSV-2, HHV-6A, HHV-6B, and HHV-7 increased the risk of participants developing dementia.
Another study in Taiwan found anti-herpes drugs prevented dementia in 90 percent of participants.
How the drugs might work
Here’s how the drug treatment is thought to work.
Nearly everyone has at least one strain of herpes.
It can manifest as things like chickenpox or cold sores or genital herpes, but then it goes dormant — for months or years or decades.
If and when the strain does reawaken later on, it can sometimes take different forms and cause different conditions. The strain that causes chickenpox, for instance, can later show up as shingles.
It’s possible some of those strains could reawaken and show up in the brain to cause or worsen dementia.
But because of that long dormancy, proving that connection or causality is a waiting game.
The Valtrex clinical trial, for example, isn’t expected to have results until 2022.
Itzhaki proposes a vaccine for HSV-1 as an even better option than an antiviral treatment. However, she notes there isn’t one yet, and a vaccine trial “would presumably have to extend for many years to find the outcome.”
So, there will remain for at least a while a possibility that the current evidence of a connection is being influenced by some overlooked factor.
“It has to be replicated in other countries,” Itzhaki said. “It’s very unlikely but not impossible that there could be some sort of peculiar local effect.”
Other possible factors
There’s also the possibility there could be something associated with the herpes virus — but not the virus itself — that may be upping the risk of dementia, Itzhaki adds.
For instance, herpes might’ve made it more likely that people have certain types of bacteria that, possibly, increase the risk of dementia.
Or both herpes and the bacteria could be risk factors or causes.
Some research has found a connection between some oral bacteria and dementia.
Itzhaki notes in her paper that bacteria could be “leading to the disease in the sizeable proportion of [Alzheimer’s] patients whose illness is not accounted for by HSV1.”
Trials that target herpes viruses specifically would be able to determine whether they’re at least one of the causes. But they might not stave off all dementia in all patients, even if herpes is a cause of dementia.
“Treatment is going to be tried, which might or might not work. It might not work because of other factors that have been overlooked,” Itzhaki said. “But if it doesn’t work, it won’t be because the concept [of a herpes-dementia connection] is wrong. It will be because of other stuff interfering.”
But she’s eager to get started investigating.
Data on a possible herpes cause for dementia has “been ignored or dismissed for three decades, very unfortunately for those who developed [Alzheimer’s] during that period and who therefore had no chance of benefiting from the information,” she writes in the paper.
She adds that “surely, now is the time to rectify the situation” by finding a treatment.
The bottom line
As evidence accumulates that herpes may increase the risk of developing dementia, clinical trials are starting to test that connection.
These trials may lead to a treatment that might prevent dementia, including Alzheimer’s.
Results would still be many years away, but a new paper lays out a road map for how that research could progress and what new treatments might work.