Shingles vaccine's potential impact on dementia risk examined
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In a groundbreaking study conducted by researchers at Stanford Medicine, the link between the shingles vaccine and the risk of dementia has been explored. The research focuses on older adults in Wales, specifically those born on or after September 2, 1933, who were eligible for the live-attenuated shingles vaccine (Zostavax).
The study, which employs a regression discontinuity design, offers promising results. It suggests that the shingles vaccine could potentially protect the brain, with reductions in dementia risk ranging from about 17% to 33%, depending on the study and population examined.
One key finding is a natural experiment in Wales, where individuals born just after a cutoff date for shingles vaccine eligibility at age 70 received the vaccine while those born before did not. This design approximates a randomized trial by comparing similar groups around a policy cutoff, helping infer causality. The study revealed an approximately 17% reduction in dementia incidence among vaccinated individuals compared to unvaccinated controls.
Large retrospective cohort studies in the U.S. have also found that the newer shingles vaccine, Shingrix (recombinant zoster vaccine, RZV), is associated with an 18-33% lower risk of all-cause dementia compared to unvaccinated or flu-vaccinated groups.
The protective effect may involve prevention of herpes zoster virus reactivation and related neuroinflammation believed to contribute to dementia pathology. Additionally, the adjuvant AS01 used in Shingrix may have immune-modulatory effects that further reduce dementia risk.
However, it's important to note that while these observational studies provide strong evidence of association, they cannot fully prove causality. Further research is ongoing to confirm mechanisms and causal effects.
The shingles vaccine is recommended for adults aged 50 and older, particularly those at higher risk of dementia, as it may provide both direct protection against shingles and a secondary benefit in lowering dementia risk.
Interestingly, the study found that the effect of the vaccine on reducing dementia risk was significantly stronger in women compared to men. Women in the study group who received the shingles vaccine experienced a 20% lower chance of developing dementia over the next seven years.
Pascal Geldsetzer, M.D., Ph.D., one of the researchers, stressed the need for randomized clinical trials before making firm claims about the vaccine's effect on dementia risk. Despite this, the study's results suggest that the shingles vaccine may have a protective effect against dementia, beyond its effects on shingles itself.
The study's findings could potentially lead to further research into the mechanisms by which the shingles vaccine may reduce the risk of dementia. The study's results may also be significant for public health recommendations regarding the shingles vaccine and its potential benefits for reducing the risk of dementia.
It's worth mentioning that the group eligible for the shingles vaccine had a 47.2% vaccination rate, while the group just before the birthdate cutoff had only a 0.01% vaccination rate. This disparity in vaccination rates could have implications for public health strategies aimed at increasing vaccination rates among older adults.
In conclusion, emerging evidence from natural randomized trials and regression discontinuity designs supports that shingles vaccination is linked to a substantial reduction in the risk of dementia. However, definitive causal proof awaits further research. These findings highlight shingles vaccination as a promising potential intervention for dementia prevention in older adults.
The shingles vaccine, such as Shingrix, might not only protect against shingles but also promote health-and-wellness by potentially reducing the risk of dementia, particularly in older women. Meanwhile, the ongoing research on the mechanisms and causal effects of the shingles vaccine on mental-health aspects like dementia continues to gain significance in the field of science.
