Study links shingles to increased risk of cognitive decline

MADRID, (EUROPA PRESS). – A new study led by researchers at Brigham and Women’s Hospital (United States) found that a shingles outbreak is associated with a 20 percent higher long-term risk of subjective cognitive decline.

According to the researchers, the study’s findings support the idea of ​​getting vaccinated against shingles to reduce the risk of contracting it. The results are published in Alzheimer’s Research & Therapy.

“Our results show the long-term implications of shingles and highlight the importance of public health efforts to prevent and promote shingles vaccine uptake,” said senior author Sharon Curhan.

“Given the increasing number of Americans at risk for this painful and often disabling disease and the availability of a highly effective vaccine, shingles vaccination could provide a valuable opportunity to reduce the burden of shingles and possibly reduce the burden of subsequent cognitive decline,” he added.

Shingles, medically known as herpes zoster, is a viral infection that often causes a painful rash. Shingles is caused by the varicella-zoster virus (VZV), the same virus that causes chickenpox. After a person has chickenpox, the virus stays in their body for the rest of their life. Most of the time, the immune system keeps the virus at bay. Years or even decades later, the virus can reactivate as shingles.

Nearly all Americans over the age of 50 have been infected with VZV and are therefore at risk for shingles. There is increasing evidence that herpes viruses, including VZV, may influence cognitive decline. Subjective cognitive decline is an individual’s self-perceived experience of worsening or increased frequency of confusion or memory loss. It is a form of cognitive decline and one of the first noticeable symptoms of Alzheimer’s disease and related dementias.

Previous studies on shingles and dementia have been conflicting. Some research suggests that shingles increases the risk of dementia, while others suggest no association or a negative association. In recent studies, the shingles vaccine was associated with a reduced risk of dementia.

To learn more about the relationship between shingles and cognitive decline, Curhan and her team used data from three large, well-characterized studies of men and women over long periods: the Nurses’ Health Study, the Nurses’ Health Study 2, and the Health Professionals Follow-Up Study.

The study included 149,327 participants who completed health status surveys every two years, including questions about shingles episodes and cognitive decline. Those who had shingles were compared with those who had not.

Curhan co-designed the study with first author Tian-Shin Yeh, a former fellow at the Harvard T.H. Chan School of Public Health. The researchers found that a history of shingles was significantly and independently associated with an increased risk—about 20 percent higher—of subjective cognitive decline in both women and men. The risk was highest among men who carried the APOE4 gene, which is linked to cognitive decline and dementia. The same association was not true for women.

Researchers don’t know the mechanisms that link the virus to cognitive health, but there are several possible ways it may contribute to cognitive decline. There is growing evidence linking VZV to a vascular disease called VZV vasculopathy, in which the virus causes damage to blood vessels in the brain or body. Curhan’s group previously found that shingles was associated with an increased long-term risk of stroke or heart disease.

Other mechanisms that may explain how the virus can cause cognitive impairment include brain inflammation, direct damage to nerve and brain cells, and activation of other herpesviruses.

Limitations of this research include that it is an observational study, that the information is based on self-reports, and that it included a predominantly white and highly educated population. In future studies, researchers hope to learn more about the prevention of shingles and its complications.

“We are looking at whether we can identify risk factors that could be modified to help reduce people’s risk of developing shingles,” Curhan said. “We also want to study whether the shingles vaccine can help reduce the risk of adverse health outcomes from shingles, such as cardiovascular disease and cognitive decline.”