Study links shingles infection to cognitive decline: 'Long-term implications'

A study has discovered that having shingles once may increase the likelihood of experiencing long-term confusion and memory loss.

A study led by Brigham and Women's Hospital and Harvard Medical School found that the virus is associated with a higher risk of "subjective cognitive decline," as stated in a Harvard press release.

The journal Alzheimer's Research & Therapy published the findings on Aug. 14.

Early cognitive changes can be detected before they become apparent on standard neuropsychological tests, according to Sharon Curhan, M.D., a physician and epidemiologist at Brigham and Women's Hospital in Boston.

Mild cognitive impairment (MCI) and dementia were also linked to it.

According to Curhan, shingles may increase the risk of dementia through neuroinflammation, cerebral vasculopathy, or direct neuronal damage.

Over a 13-year period, data from three large cohorts of over 150,000 women and men was analyzed by researchers in this study.

According to Curhan, the data was obtained from the Nurses' Health Study, the Nurses' Health Study II, and the Health Professionals Follow-Up Study.

"We were surprised by the large magnitude and long duration of the increased risk."

She stated that the magnitude of the elevated risk may be greater among those who did not receive the shingles vaccine.

The study found that individuals who had shingles experienced a more than 20% increased risk of long-term cognitive decline.

The increased risk was of a large magnitude and duration, and it may differ between women and men, according to Curhan, who shared this with Planet Chronicle Digital.

Women who were not APOE e4 carriers had a higher risk of developing Alzheimer's disease than men who were not carriers, but the risk was even higher among APOE e4 carriers, particularly men.

Dr. Marc Siegel, a senior medical analyst for Planet Chronicle, stated that while he acknowledges that this is an observational study and cannot establish a cause-and-effect relationship, he believes "the observation is real."

"The reactivation of a virus that has been dormant in nerves can cause inflammation, and when this inflammation affects the brain, it can lead to cognitive decline and potentially Alzheimer's disease, as stated by the expert to Planet Chronicle Digital."

Research has examined the link between herpes zoster and other viruses and the development of Alzheimer's and dementia-related diseases, as stated by Heather M. Snyder, PhD, senior vice president of medical and scientific operations at the Alzheimer's Association in Chicago.

Snyder, who was not involved in the study, told Planet Chronicle Digital that it is unclear if the virus is present in individuals due to changes associated with cognitive decline, immune system changes, or some sort of cause and effect.

"When inflammation involves the brain, it is associated with cognitive decline."

A history of shingles is linked to a higher long-term risk of a major cardiovascular event, such as a stroke or heart attack, which could persist for many years after infection, according to Curhan.

What to know about shingles

The CDC states that shingles, or herpes zoster, is a painful rash resulting from the varicella-zoster virus (VZV), which is also the cause of chickenpox.

The rash and blisters usually scab over within seven to 10 days.

In the U.S., approximately one out of every three individuals will experience the infection at some point in their lifetime.

According to Snyder, a significant number of adults carry the herpes zoster virus in their brain cells due to a past infection.

Besides the rash, which usually manifests as a band across the body or face, symptoms may include fever, chills, headache, and nausea, according to the CDC.

Complications like long-term nerve pain can result from the virus in some cases (10% to 18%).

One in every three people in the U.S. will have shingles in their lifetime.

The CDC reports that in addition to the common side effects, rare but severe consequences can occur, such as vision loss, bacterial infections, pneumonia, brain inflammation (encephalitis), hearing impairment, and even death.

These complications are most likely to affect those with compromised immune systems.

Antiviral treatments and pain relief medications are available for those with the condition.

Means of prevention

Shingles has long-term implications, as shown by these findings, emphasizing the significance of public health initiatives to prevent the infection, according to Curhan.

According to the CDC, the vaccination has been proven to be 90% effective in preventing infection and long-term nerve pain in adults aged 50 and above with healthy immune systems.

According to Curhan, shingles vaccination could be a valuable opportunity to reduce the burden of subsequent health issues due to shingles, such as chronic pain, cardiovascular complications, or cognitive decline and dementia, given the growing number of Americans at risk for this painful and often disabling disease and the availability of an effective vaccine.

People aged 50 and above should receive routine shingles vaccinations, according to the CDC, regardless of whether they have experienced shingles before or have received a previous vaccine.

Health care providers should be consulted by anyone who may be eligible for the vaccine or who has questions or concerns about vaccination, according to Curhan.

Siegel echoed the merits of vaccination.

The shingles vaccine (Shingrix) is crucial for individuals over 50 who have had chicken pox or the varicella vaccine to reduce the likelihood of shingles virus reactivation and associated complications, according to the researcher.

Potential limitations

Curhan pointed out that the observational study primarily focused on a White, highly educated population, which suggests that future studies in other populations could enhance the research.

Furthermore, we lacked vaccination status data for the entire study population, which limited our ability to investigate this relationship in the entire sample.

The shingles vaccine was not widely available during much of the study period, and its uptake was generally low, according to Curhan.

The more recent vaccine was not available until after the study.

"Additional studies evaluating the relationship between shingles vaccination status and cognitive decline risk would be informative as the uptake of the newer shingles vaccine increases," Curhan said.

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"We are currently gathering this information from our participants and aim to carry out these studies in the future."