A recent study has uncovered a surprising connection between the shingles vaccine and a reduced risk of dementia. The findings suggest that the vaccine may offer more than just protection against the painful rash caused by shingles.
By analyzing the health records of over 200,000 individuals, the researchers discovered that the findings could potentially revolutionize our understanding of the complex relationship between viral infections and cognitive decline.
The Evolution of Shingles Vaccines
Shingles, caused by the reactivation of the varicella-zoster virus, has long been a concern for older adults. The previous vaccine, Zostavax, provided protection for about five years. However, Shingrix, developed using newer vaccine technology, offers stronger and longer-lasting immunity.
In November 2023, Shingrix replaced Zostavax on the National Immunisation Program in Australia, making it freely available to those at highest risk of shingles complications, including adults aged 65 and over, First Nations people aged 50 and older, and younger adults with certain immune-compromising medical conditions.
A Groundbreaking Study
Researchers in the United Kingdom seized the opportunity presented by the transition from Zostavax to Shingrix in the United States. By analyzing electronic health records, they compared 103,837 people who received Zostavax between 2014 and 2017 with an equal number who received Shingrix.
The results were astonishing: those who received Shingrix experienced a 17% increase in “diagnosis-free time” during the six-year follow-up period, translating to an average of 164 extra days without a dementia diagnosis.(ref)
The study used a unique “natural experiment” design. The rapid switch from Zostavax to Shingrix in the US allowed researchers to compare outcomes in a large population before and after the change, minimizing potential confounding factors.
By the end of the study, about the same proportion in each group had developed dementia, but those who received Shingrix were diagnosed significantly later on average.
Gender Factor
Interestingly, the benefits of Shingrix in terms of dementia risk were more pronounced for women. This finding aligns with the known higher risk of dementia in women due to various biological factors, such as increased sensitivity to certain genetic mutations and hormonal differences.
Women are disproportionately affected by Alzheimer’s disease, the most common form of dementia. Nearly two-thirds of Americans with Alzheimer’s are women.(ref)
Researchers believe this disparity is influenced by a complex interplay of factors, including longer life expectancy, biological differences, and unique life experiences. The more pronounced protective effect of Shingrix in women offers an intriguing avenue for further research into gender-specific dementia prevention strategies.
The Infection-Dementia Link
The idea that vaccinations against viral infections could lower the risk of dementia is not new.
Previous research has shown associations between vaccines for diphtheria, tetanus, polio, and influenza and reduced dementia risk. Notably, untreated infections with the herpes simplex virus, closely related to the varicella-zoster virus that causes shingles, have been linked to an increased risk of Alzheimer’s disease.
Several studies have suggested that viral illnesses may play a role in the development of dementia. For example, human herpesvirus 6A (HHV-6A) and human herpesvirus 7 (HHV-7) have been found in postmortem brain tissue samples of people with Alzheimer’s disease at levels up to twice as high as non-Alzheimer’s samples.(ref)
Researchers have also proposed that herpes simplex virus 1 (HSV-1), in combination with the APOE4 gene, may considerably increase Alzheimer’s risk.
Potential Mechanisms
While the exact mechanisms behind the shingles vaccine’s protective effect against dementia remain unclear, researchers have proposed two potential pathways:
- Certain molecules produced during fetal development, which can cause inflammation and accelerate aging, may be reactivated by viral infections like shingles in adulthood. Suppressing these infections through vaccination could hypothetically mitigate this risk.
- Specific proteins produced by viruses and harmful gut bacteria may support the toxic actions of Amyloid-β, a protein implicated in Alzheimer’s disease. In laboratory conditions, these proteins have been shown to accelerate the onset of dementia.
Further research is needed to elucidate the precise biological processes linking viral infections, the immune system, and cognitive decline.
Understanding these complex interactions could pave the way for novel preventive and therapeutic strategies targeting the infection-dementia link.
Read Next:
Nancy Maffia
Nancy received a bachelor’s in biology from Elmira College and a master’s degree in horticulture and communications from the University of Kentucky. Worked in plant taxonomy at the University of Florida and the L. H. Bailey Hortorium at Cornell University, and wrote and edited gardening books at Rodale Press in Emmaus, PA. Her interests are plant identification, gardening, hiking, and reading.
