They’re uncomfortable, embarrassing and tough to get rid of, but cold sores may also be a warning sign of dementia.
Scientists from Sweden published a paper linking the virus behind cold sores, herpes simplex virus-1 (HSV-1), to an increased risk of the memory-robbing disease.
By studying more than 1,000 elderly people over 15 years, researchers found people who had been infected with HSV-1 twice as likely to develop dementia than those who were not infected.
The scientists are unsure why the two conditions may be linked, but it may be because it hides out in your nervous system for life.
At any point, flare-ups can occur, which may cause inflammation inside the nervous system, pressing on and damaging the delicate tissue of the nervous system and brain.
The theory goes that over time, this could lead to some of the changes associated with dementia, like memory loss, brain tissue break down and confusion.
This is just the latest in a series of papers investigating a connection between common viruses and the risk of dementia later in life.
Recently, scientists have also linked the varicella-zoster virus, which is behind chicken pox and shingles, to changes in brain health.
Cold sores are caused by Herpes simplex virus 1. A different strain of the same virus causes the STD leading to genital herpes
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Still, experts say the evidence is mixed, and other studies have found no link between the virus and cognitive decline.
HSV-1 affects between 50 and 80 percent of American adults, according to Johns Hopkins. This virus is similar to, but not the same as, the virus that causes the STD herpes, which is called HSV-2.
The virus is mainly spread through intimate person-to-person contact, like kissing or oral sex, though in some rare cases it can be spread through sharing drinks.
It can also be spread from mother to child in the womb, and can cause serious side affects in children.
Once someone catches the disease, many of the symptoms are manageable and mild. Initial signs include fever, swollen lymph nodes, sore throat and sores inside the mouth and gums.
After the initial flare up, symptoms may disappear completely, before popping up periodically on the side of the mouth or lip as a red, ulcerous sore.
During one of these flare ups, doctors may prescribe antiviral medication or ointment to ease discomfort or instruct patients to take over-the-counter painkillers like ibuprofen to manage inflammation.
For a long time, doctors thought this unsightly visitor was one of the only lingering effects of the disease.
However, in recent years, a more worrying link has emerged.
This includes the team of researchers from Uppsala University, who published their findings in December 2023 in the Journal of Alzheimer’s Disease.
Their study followed 1,002 Swedes, of which 80 percent carry HSV-1, over 70 years old for a 15-year period.
They adjusted for factors like education status and genetic predisposition to Alzheimer’s.
By the end of the study, 32 subjects had developed Alzheimer’s disease and 63 percent had developed another form of dementia – in total representing 11 percent of the participants. Eighty-nine percent of those people had herpes.
Researchers then compared these people to the rest of the group, which hadn’t developed dementia by the end of the study, in which 82 percent of participants had herpes.
Jim Carrey’s HSV-1 and HSV-2 diagnosis became public amid a lawsuit from an ex-girlfriend in 2017 that claimed the actor did not inform her about his condition
After adjusting for some factors that may have affected the data, they concluded those who caught herpes were two times more likely to have developed some form of neurodegeneration.
They note that their limitations include they could not adjust for the affect age may have on the data, nor could they rule out other factors like medications, heart disease and diabetes.
In the US, an estimated 4 percent of adults over 65 have dementia. By comparison, experts at Johns Hopkins estimate between 50 and 80 percent of the populous has HSV-1.
Their paper isn’t the first to link the two.
A 2024 study from researchers in South Korea that used data from a national health insurance service including more than 750,000 people, found people who had HSV and varicella zoster virus (VSV) were more likely to develop dementia.
However, not all the studies investigating these two factors have found a link. A 2019 review from multiple universities in the UK found the link between dementia and HSV-1 was inconclusive, and didn’t establish a strong association.
Dr Jagan PillaI, a cognitive neurologist at the Cleveland Clinic told Parade the studies are not convincing enough to conclude that herpes could cause dementia. Of the 2019 study from the UK, he said: ‘it supports the need for better quality future studies.’
In addition, Dr Monica Gandhi, an infectious disease specialist at UC San Francisco, told Medical News Today the rates of herpes infections in general are much higher than the rates of dementia.
This difference, she said, is evidence that they might not be linked.
She said: ‘Given how common herpes virus infection is [in] young people, I would not let this study concern you too much.’
