Shingles linked with higher risk of experiencing cognitive decline

Share on Pinterest
If a person has had shingles, they are at higher risk of subjective cognitive decline, which may lead to further cognitive issues, says a new study.
Anyone who has had chickenpox in their lives is at risk of getting shingles due to its virus that never leaves the system, and which causes shingles.
The study underscores the value of being vaccinated against shingles.
Men with a certain gene are at somewhat higher risk of cognitive issues than women.
People who have had shingles, or herpes zoster, at some point in their lives have an increased risk of developing subjective cognitive decline later on, says a new study from Brigham and Women’s Hospital, in Boston, MA.
shingles
The study, which appears in Alzheimer’s Research & Therapy, finds a 20% increase in the chances that a person will eventually experience a sense of cognitive decline if they have had shingles.
Alzheimer’s Research & Therapy
Research regarding a connection between herpes zoster and cognitive issues has been inconclusive. However, there have been several studies recently that have established a link between higher rates of shingles vaccinations and lower rates of dementia, which is essentially a confirmation of the same relationship.
studies
dementia
Shingles is a product of the varicella zoster virus (VZV), the same virus that causes chickenpox. After chickenpox resolves, the virus remains in the body. Anyone who has had chickenpox still carries the VZV virus, and may develop shingles unless they are vaccinated against it.
Almost all adults over the age of 50 in the United Sates are likely to carry the VZV virus due to the prevalence of chickenpox in their childhoods.
The recent study also found that having had shingles carried a higher risk of subjective cognitive decline for men who carried the gene APOE4 — associated with cognitive impairment and dementia — compared to women.
What is ‘subjective’ cognitive decline?
Subjective cognitive decline, or SCD, “is a state when self-perceived cognitive decline is present, but objective cognitive impairments cannot be detected,” explained the first author of the study, Tian-Shin Yeh, MD, MMSc, PhD, a postdoctoral fellow at Harvard University, speaking to Medical News Today.
Tian-Shin Yeh, MD, MMSc, PhD
Ozan Toy, MD, MPH, of Neuropsychiatric Consultants, PC, who was not involved in the study, also told us that: “[SCD] is what it sounds like. A patient [with SCD] may feel that they are having issues with their memory or other cognitive functions. It may not be detected either through conversation with a physician, or it may not be detected through formal cognitive testing.”
Ozan Toy, MD, MPH
“With normal aging, it’s not uncommon for many people to feel their memory is not quite as sharp as it used to be, and maybe they don’t tend to recall things as well as they used to. But then when you actually go into the clinic, and they do objective testing, we may not actually really see anything that’s objectively sort of wrong, if you will,” Toy added.
If no issue is found, “[t]hat doesn’t necessarily mean that there’s no objective problem per se. It could be missed,” he also cautioned. That may be because “[w]hat’s commonly used in neurology clinics is a mini-mental status examination, where you’re assessing a patient who may potentially be at risk for mild cognitive impairment.”
For a more thorough examination, said Toy, “sometimes we do neuropsychological testing, which is a very comprehensive battery of cognitive tests performed by a neuropsychologist. And that’s really the most detailed testing that you could do for a patient in terms of their cognitive function.”
Can subjective cognitive decline progress to dementia?
While SCD may be mild, the concern is that it may lead to more serious cognitive issues later on.
Noting that “not everyone will progress to mild cognitive impairment [MCI] or dementia, some studies have shown that people with SCD have a higher risk of progression to MCI and dementia,“ Yeh told us.
“For instance, about 7% progress to dementia and 21% to mild cognitive impairment,” she explained, adding that “[t]hose with SCD have about 2.2 times higher risk of developing dementia compared to those without SCD.”
As for the link with genetic risk, the study’s finding of a higher incidence of SCD among men with the APOE4 gene remains unexplained for now.
“This sex difference,” said Yeh, “is intriguing but not yet fully understood. Previous research has shown sex differences in how the APOE genotype and other risk factors relate to Alzheimer’s disease and neurodegeneration.”
“These differences could be due to genetic factors, hormonal influences, or differences in how [Alzheimer’s] pathology develops in men versus women.”
Yeh called for further research to better understand the mechanisms behind these sex-specific effects.
‘Vascular connection’ between shingles and cognition
Yeh explained that “[t]he varicella zoster virus (VZV) has been associated with increased risk of vascular diseases, including stroke.”
stroke
“Data from our cohorts showed that herpes zoster was associated with up to 38% higher long-term risk of stroke, persisting for 12 years or longer,” she added.
“This vascular connection may be relevant to cognitive decline and dementia risk because cerebrovascular changes, even at a subclinical level, can contribute to cognitive impairment. Inflammation and direct neuronal damage from VZV reactivation [after post-chickenpox dormancy] may play a role. The link between VZV, vascular health, and cognitive outcomes highlights the complex interplay between infectious agents, vascular health, and brain function as we age.”
– Tian-Shin Yeh, MD, MMSc, PhD
The most important takeaway from the study is that provides another compelling reason to get vaccinated against shingles if you have not already done so.