A recent study published by researchers at the Harvard-affiliated Brigham and Women’s Hospital has identified a troubling correlation: those who suffer from shingles could face a 20% higher risk of long-term subjective cognitive decline, which is among the first indicators of Alzheimer's disease and other dementias. The study, appearing in Alzheimer's Research & Therapy, highlights an increased concern for the nearly universal demographic over 50 in the U.S., who carry the varicella zoster virus (VZV) responsible for both chickenpox and shingles.
While the mechanics of how VZV interacts with cognitive functions are still not fully understood, evidence points to the fact that almost all those past the half-century mark are at potential risk for the virus's reactivation, which may be linked to cognitive impairments and memory loss; perhaps in part due to VZV's associated vascular diseases or its direct effect on nerve and brain cells, this association was highlighted by Sharon Curhan of the Channing Division for Network Medicine at BWH, who stated, “Given the growing number of Americans at risk for this painful and often disabling disease and the availability of a very effective vaccine, shingles vaccination could provide a valuable opportunity to reduce the burden of shingles and possibly reduce the burden of subsequent cognitive decline,” as reported by The Harvard Gazette.
Previous examinations of the relationship between shingles and cognitive health have not always been consistent, with certain studies indicating an increase in dementia risk post-shingles, while others show no significant correlation. Notably though, recent indicators suggest that immunization against shingles may lead to a lower risk of dementia; this angle was probed by accessing data from three expansive studies—the Nurses' Health Study, the Nurses' Health Study 2, and the Health Professionals Follow-Up Study—encompassing 149,327 individuals who provided health updates biennially, including any episodes of shingles and their experiences with cognitive decline.
In the light of this research, scientists uncovered that a history of shingles was significantly and independently linked with a roughly 20 percent elevation in the hazard of subjective cognitive decline in both sexes, yet intriguingly, it's worth noting that this risk was particularly pronounced in men carrying the APOE4 gene associated with dementia, the study, helmed by Curhan and first author Tian-Shin Yeh, formerly of the Harvard T.H. Chan School of Public Health, stressed that further inquiry is vital, as Curhan pointed out, "We’re evaluating to see if we can identify risk factors that could be modified to help reduce people’s risk of developing shingles," as noted by The Harvard Gazette.
Despite the study's strengths, its limitations are as informative as its findings: its observational nature, reliance on self-reported data, and a participant pool primarily composed of white, highly educated individuals signal the need for a broadened scope in future research endeavors. With backing from GlaxoSmithKline Biologicals SA Supported Studies Programme Protocol 216148, these researchers aim to not only better understand shingles and its implications on health outcomes like cognitive decline and cardiovascular disease but also possible preventative measures, including immunization efficacy.
