Research points to a possible link between shingles and cognitive decline. Here's what to know.
Key Takeaways
Cognitive decline is a major public health issue in the US, and shingles could be contributing to its occurrence, according to new research published in Alzheimer’s Research & Therapy.
Researchers looked at 149,327 participants and found that shingles was associated with a higher long-term risk of cognitive decline.
Patients should get the shingles vaccine if possible.
An episode of shingles—a painful, bubbling rash that erupts in patients who’ve had chickenpox—is associated with a significantly higher long-term risk of subjective cognitive decline (SCD), a new study published in Alzheimer’s Research & Therapy has found.[]
The shingles, or herpes zoster virus, lies dormant in the body in people who’ve had chickenpox (the varicella-zoster virus, or human herpesvirus 3), David Cutler, MD, a board-certified family medicine physician at Providence Saint John’s Health Center in Santa Monica, CA, tells MDLinx.[]
“[Shingles] lives in the nerve ganglia, and [when activated] climbs up along the nerves, causing pain and a rash,” Dr. Cutler says. A suppressed immune system or a coexisting infection could trigger a reactivation of the virus, which shows up as shingles and not chickenpox. Age could also play a role. However, Dr. Cutler notes, triggers for shingles aren’t entirely understood.
When improperly treated or left untreated, the fiery, tingling nerve pain can persist for months or even years, Dr. Cutler says. It can lead to long-term nerve pain called postherpetic neuralgia in the area where the rash was located.[]
Another long-term complication? Researchers now think shingles are associated with SCD, the self-reported experience of worsening or more frequent confusion, memory loss, and inability to learn or make judgments, according to the Centers for Disease Control and Prevention (CDC).
SCD occurs early on in patients with Alzheimer’s disease and other dementias, and it can play a major role in reducing a patient’s autonomy and quality of life. It isn’t a diagnosis, as it refers to one’s subjective experience, but it can indicate greater cognitive concerns. In the United States, cognitive decline is a public health problem, with around 11% of people over age 45 experiencing SCD.[] It tends to occur more often in those over the age of 65, although it does also occur in those between the ages of 45 and 64. SCD occurs more frequently in Black and African American populations.[]
A closer look at the study
To determine SCD in patients with and without shingles, the researchers looked at the association between shingles and SCD in 149,327 participants across three large cohorts. These included the Nurses’ Health Study (NHS), NHSII, and Health Professionals Follow-Up Study (HPFS). The researchers calculated risk by looking at SCD scores relative to years since shingles occurred, and compared these findings to patients without a history of shingles.
The findings
Across the cohorts, shingles were associated with an approximately 20% higher long-term risk of SCD.
In the NHS cohort, patients who had shingles 13 years or longer ago saw a higher long-term risk of SCD compared to patients without shingles.
In the NHS II cohort, shingles was associated with higher risk of SCD in both the short term (1–4 years) and long term (13 years or more) since shingles was found.
In the HPFS cohort, SCD risk was higher no matter the timeline since a patient had shingles. In patients with data on APOE ε4—the strongest genetic risk factor for Alzheimer's disease (AD)—the researchers believe the risk for SCD may be higher in male APOE ε4 carriers vs women.[]
There was also an association between a higher long-term risk of SCD in women without a shingles vaccination, but additional research is needed in this area.
The researchers concluded that “herpesviruses may influence the risk of cognitive decline and dementia…through neuroinflammation, cerebral vasculopathy, or direct neuronal damage.”[]
That said, evidence of the relationship between shingles and SCD is conflicting. Despite the findings from the previously mentioned three cohorts, other studies have found no association at all, while others still have found a lower risk of dementia in those who’ve had shingles.
The researchers also noted that findings are inconclusive regarding whether or not vaccination against shingles plays a role in preventing cognitive decline. They say that high-quality prospective cohort studies are needed to better understand this relationship.
There is no conclusive way to prevent SCD, but researchers believe that exercise, healthy diet, and vascular risk management are key. Shingles prevention could also play into risk mitigation.[]
What this means for you
Patients should be educated on risks associated with shingles, especially patients over 50 or those who are immunocompromised.[] Even though vaccination against chickenpox ramped up in the mid-90s (meaning chickenpox cases have reduced by 97%), there is a whole generation of people in their 30s and 40s who haven’t had the vaccination and are therefore at risk of getting shingles.[] More so, Dr. Cutler says, shingles can occur more than once, despite there being the pervasive myth that it cannot. “After having shingles, the body’s immunity against shingles rises again…but only for a time. So you can get it again,” he says. The CDC also recommends that patients over 50 get the shingles vaccine.[]