The dementia It is one of the main causes of disability and dependency among older people worldwide, with more than 57 million people affected in 2021 and almost 10 million new cases a yearaccording to the World Health Organization (WHO). In turn, the shinglescaused by the reactivation of the varicella-zoster virus (the same as chickenpox), affects up to a third of adults throughout their lives and its incidence increases with age, especially after the age of 50.
Given these numbers, a recent association between both pathologies that could be the key, even more so in prevention: vaccination against this infection could result in fewer cases of cognitive decline in old age and dementiaaccording to a study.
Both diseases disproportionately affect older adults and women, both due to a higher prevalence and the associated burden of care. Dementia, which encompasses different disorders – mainly Alzheimer’s – represents the seventh cause of death globally and creates enormous challenges for families and health systems.
Faced with this panorama, science has begun to illuminate a crucial link: repeated reactivation of varicella-zoster virus may contribute to dementia riskand getting vaccinated against shingles appears to be one of the few preventive strategies with real potential to mitigate that risk.
This is demonstrated by a recent large-scale study published in Nature Medicine and spread by Washington Postwhich documented that Reducing virus outbreaks through vaccines may result in fewer cases of cognitive decline in old ageespecially among women and older adults.
When the varicella-zoster virus causes chickenpox in childhood, remains dormant in the nervous system for decades. In adulthood, with aging or immunosuppression, it can reactivate as herpes zoster, an infection that, beyond the pain and rash, begins to be unequivocally associated with neurological damage.
“The big question was whether this reactivation only generated physical discomfort or whether it also left a lasting imprint on the brain,” he said. Anupam Jenainternist at Massachusetts General Hospital, in conversation with Washington Post.
The study published in Nature Medicine followed the medical records of more than 100 million Americans and showed that those who had two or more episodes of shingles presented a 7% to 9% increased risk of dementia in the following years, compared to those who only went through one outbreak.
The hypothesis: each new reactivation triggers an intense inflammatory responsecapable of subtly but persistently damaging brain areas linked to memory, attention and cognitive processing.
“Dementia is determined by genetic, metabolic and environmental factors, but this finding suggests that reducing viral load over time—and avoiding multiple reactivations—could become a concrete tool to mitigate the risk,” he explained. Patrick Schwabsenior director of artificial intelligence at GSK and co-author of the research.
Complementary studies, such as Baltimore Longitudinal Study of Aging published in Neurologyverify that symptomatic herpetic infections are associated with accelerated loss of white matter volume —especially in the temporal lobe— and progressive decrease in attention span.
Although not all studies agree on the magnitude of the effect, the trend is clear: More Episodes of Shingles Equate to Higher Risk of Cognitive Decline in the next decade of life.
The great novelty of recent years is that the Shingles vaccination not only protects against painful outbreaksbut also reduces the risk of dementia significantly. By analyzing millions of patients, work in Nature Medicine documented that immunized people presented 27% to 33% lower risk of dementia in the three years after application.
This effect varies depending on the type and number of doses: those who received two doses of the recombinant regimen Shingrix enjoyed greater protection (27% less at three years; 17% less at five years), and this benefit was especially visible in women over 80 years oldwhich reached up to a 39% less risk three years after vaccination.
The comparison with the previous vaccine, Zostavax (now withdrawn in several countries), shows additional advantages: those who received both doses of Shingrix had a 18% less risk than those immunized with Zostavax at five years of follow-up. “The results were really remarkable for their consistency,” Schwab said. Other studies, reviewed in Systematic Reviews & Meta-Analysis (2024), confirm a global reduction of up to 32% after vaccination.
However, protection is not indefinite: “When the vaccine action is attenuated, both the incidence of herpes zoster and the risk of dementia tend to rebound, which suggests that we may need booster doses in the medium or long term,” he clarified. Schwab.
The vaccination It is safe, widely available and recommended by the WHO for people over 50 years of age and immunosuppressed patients. “You want to have five more years to play with your grandchildren and five more years to drive very well. That is priceless,” summarized the neurologist. A. M. Barrett of the Massachusetts VA Health System.
When comparing the effect with other vaccines recommended in older adults, such as flu or tetanus, studies show that observed protection against dementia is more robust with shingles vaccines.
A study led by Maxime Taquet at the University of Oxford, for example, highlights that those who received Shingrix lived, on average, 164 more days without a dementia diagnosis in the six years following immunization, compared to those who received other vaccines. This benefit, although it may seem modest, takes on enormous relevance at a population level, considering the magnitude and continuous advance of the dementia epidemic.
There are still open questions about biological mechanisms: Does the vaccine prevent the disease or only delay its appearance? Why is it more effective in women? “The dominant hypothesis is that by reducing the frequency of viral reactivation and associated inflammation, the cascade that leads to chronic neuronal damage is attenuated,” the authors conclude in Nature Medicine. However, research is ongoing to determine whether booster doses could improve and prolong the protective effect.
Not all works agree on the magnitude and generalization of these findings. A large Danish study published in Neurology (2022), which included more than 1.2 million adults, did not find an increased risk of dementia after shingles, except in the very rare cases of central nervous system infection.
“Contrary to our prediction, we observed that herpes zoster was even associated with a small relative decrease in the risk of dementia, although the difference, in absolute values, is not very relevant,” he concluded. Sigrun Schmidtmain author.
The meta-analysis More recent studies point to a balance: they find a 14% increase in the risk of post-shingles dementia, moderate attenuation by antivirals, and a greater preventive impact with vaccination.
They also warn about selection biases, differences by geographical area and multiple confounding factors, although the most robust studies use active controls and adjust for hundreds of variables to minimize these effects.
“We still do not know if the vaccine prevents or simply delays the onset of dementia, nor why it especially benefits women,” he points out. John Toddresearcher at the University of Oxford. The current consensus among experts is that the varicella-zoster virus and repeated immune and inflammatory responses are a modifiable risk factor, but not the only one nor necessarily the determining factor in all cases.
There are regional and demographic differences in the results: some studies in Asia find more marked elevations in risk than those in Europe, possibly associated with genetic factors, differences in access to treatment or their own epidemiological patterns.
Furthermore, scientists emphasize that although vaccination shows protective effects, these could be influenced by the fact that people who decide to get vaccinated tend to have better self-care behaviors and greater contact with the health system. “What we see may be partially mediated by variables that we have not yet been able to fully measure or control,” he warns. Patrick Schwab.
Another open question refers to the duration of protection and the difference between preventing the onset of dementia or just postponing it. Analysis of long-term data suggests that, although risk curves diverge after vaccination, they tend to converge again as efficacy decreases (as shown by the experience with Zostavax in more than a decade of follow-up), which reinforces the need to propose dynamic strategies for populations at risk.
Science still needs to unravel whether the protective effects are equally robust for different subtypes of dementia (such as Alzheimer’s, vascular, frontotemporal) and, above all, in which demographic groups vaccination campaigns should be prioritized if a greater benefit is sought on a population scale.
Shingles: symptoms and prevention
- Pain, itching, tingling, or numbness preceding the rash; blisters on a side band of the body or face. In some cases, fever, headache and fatigue.
- If it affects the ocular area, it is an emergency: consult immediately.
- The Shingrix recombinant vaccine is indicated for people over the age of 50, even in those who have already had shingles.
Dementia: warning signs and recommendations
- Frequent forgetfulness, difficulty following conversations, disorientation, mood swings, problems performing daily tasks.
- Keeping the mind and body active, socializing, eating healthy, and controlling vascular risk factors protect the brain in the long term.
- Consult if there are any signs of cognitive impairment, for early diagnosis and better opportunities for care.
When to consult
- In the case of shingles: painful rash and blisters in older adults: go early, early antiviral treatment improves prognosis.
- Dementia: When noticing signs of memory loss or behavioral changes in family members or yourself, seek medical advice.
- Emotional and social support and support networks are key for those who live with dementia.
