Cold sores and dementia: The unexpected connection

Cold sores are annoying, unwanted, and often catch us off-guard, but new research suggests these small nuisances could be an unexpected caution flag for a much scarier health concern – dementia.

Researchers in Sweden have unearthed a link between cold sores and a heightened risk of developing the memory-stealing ailment.

In a long-term study that followed over a thousand elderly individuals for 15 years, a worrying pattern emerged.

The participants who had endured an infection by HSV-1, the pesky herpes virus that causes cold sores, were twice as likely to fall prey to dementia.

Even though the team couldn’t pinpoint a concrete reason for this alarming correlation, they theorized it might lie with the virus’s insidious behavior.

Cold sores: harbingers of inflammation?

Once inside your body, the herpes virus (HSV-1) makes its home in the nerve cells – indefinitely. It gives rise to intermittent flare-ups, which could trigger inflammation within the nervous system.

This inflammation may stress and harm the delicate tissue within your nervous system and brain.

Over time, the resulting damage might potentially set the stage for symptoms associated with dementia, like confusion, memory impairment, and gradual breakdown of brain tissue.

This new understanding adds another layer of complexity to the ongoing investigation regarding the link between common viruses and an increased risk of dementia in later life.

In fact, researchers have also implicated the varicella-zoster virus, the culprit behind ailments like chickenpox and shingles, in affecting brain health.

However, the evidence does not point unequivocally towards a positive correlation in this case, and some studies have refuted any link between these viruses and cognitive decline.

HSV-1 and us: an unwanted relationship?

According to data from Johns Hopkins University, the HSV-1 virus affects between 50 and 80 percent of American adults.

Although closely related, this virus is distinct from HSV-2, the pathogen involved in sexually transmitted herpes.

HSV-1 primarily spreads through intimate contact such as kissing or oral sex, and can even pass from mother to child in the womb, potentially causing serious side effects in children.

HSV-1: a manageable menace?

Once infected, the symptoms can be mild and manageable.

Usual initial signs include a fever, swollen lymph nodes, a sore throat, and sores on the mouth and gums.

After the first flare-up, symptoms can disappear entirely, only to reappear periodically as a red, ulcerous sore on the mouth or lip.

In such instances, doctors usually prescribe antiviral medication or suggest over-the-counter painkillers to alleviate the discomfort and manage inflammation.

For the longest time, we were under the impression that these unsightly cold sores were the only lingering effects of HSV-1, but recent years have brought a more sinister link to light.

The Swedish study: cold sores and dementia risk

The team of researchers who brought this potential link to our attention hail from Uppsala University and published their findings in the Journal of Alzheimer’s Disease in December 2023.

Their rigorous study followed 1,002 Swedes, of which 80 percent carried HSV-1, over a 15-year span.

By the end of the study, 32 subjects had developed Alzheimer’s disease and 63 percent developed some form of dementia – representing 11 percent of the participants in total.

The majority of these individuals, about 89 percent, had herpes.

Even though the team took into account factors like education and genetic predisposition to Alzheimer’s, they were unable to adjust for the effect of age or the potential impact of other health concerns like heart disease and diabetes.

A tale of two studies

The Uppsala study is not the first to explore the relationship between herpes and dementia.

A 2024 study from South Korea involving over 750,000 participants also found that those with HSV and the varicella-zoster virus were more likely to develop dementia.

However, a 2019 review from several UK universities found the link between dementia and HSV-1 inconclusive, and it failed to establish a strong association.

The verdict

Dr Jagan PillaI from the Cleveland Clinic believes the studies are not convincing enough to conclude that herpes could cause dementia.

Regarding the 2019 UK study, he suggests that we need better quality studies in future.

Along the same lines, Dr Monica Gandhi, an infectious disease specialist at UC San Francisco, points out that herpes infection rates are significantly higher than dementia rates, casting doubt on a potential connection.

“Given how common herpes virus infection is [in] young people, I would not let this study concern you too much,” she states, reassuringly.

While the link between cold sores and dementia remains tenuous, what is certain is that more comprehensive and high-quality studies are needed.

The full study was published in the journal Journal of Alzheimer’s Disease.

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