[…] Scientists at Stanford University led the research, published in Nature. They compared people born before and after they were eligible to take the shingles vaccine in a certain part of the UK, finding that vaccinated people were 20% less likely to be diagnosed with dementia over a seven year period. More research is needed to understand and confirm this link, but the findings suggest shingles vaccination can become a cost-effective preventative measure against dementia.
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the researchers took advantage of a natural experiment that occurred in Wales, UK, over a decade ago. In September 2013, a shingles vaccination program officially began in Wales, with a well-defined age eligibility. People born on or after September 2, 1933 (80 years and under) were eligible for at least one year for the shingles vaccine, whereas people born before then were not.
The clear cutoff date (and the UK’s well-maintained electronic health records) meant that the researchers could easily track dementia rates across the two groups born before or after September 1933. And because the people in these groups were so close together in age, they also shared many other factors in common that could potentially affect dementia risk, such as how often they saw doctors regularly. This divide, in other words, allowed the researchers to study older people in Wales during this time in a manner similar to a randomized trial.
The researchers analyzed the health records of 280,000 residents born between 1925 and 1942. As expected, many vaccine-eligible people immediately took advantage of the new program: 47% of people born after the first week of the eligibility date were vaccinated, while practically no one born before the cutoff date received the vaccine, the researchers noted.
All in all, the researchers calculated that shingles vaccination in Wales was associated with a 20% decline in people’s relative risk of developing dementia over a seven-year period (in absolute terms, people’s risk of dementia dropped by 3.5%). They also analyzed data from England, where a similar cutoff period was enacted, and found the same pattern of reduced dementia risk (and deaths related to dementia) among those vaccinated against shingles.
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“For the first time, we now have evidence that likely shows a cause-and-effect relationship between shingles vaccination and dementia prevention,” Geldsetzer said. “We find these protective effects to be large in size—substantially larger than those of existing pharmacological tools for dementia.”
There are still unanswered aspects about this link. Researchers aren’t sure exactly why the vaccine seems to lower dementia risk, for instance. Some but not all studies have suggested that herpes zoster and other germs that linger in our bodies can overtly cause or worsen people’s dementia, so the vaccine might be having a direct preventative effect there. But it’s also possible the vaccine is triggering changes in the immune system that more broadly keep the brain sharper, and that other vaccines could do the same as well.
Importantly, this latest study only looked at the earlier Zostavax vaccine, which has largely been replaced by the more effective Shingrix vaccine. This might mean that the results seen here are an underestimate of the benefits people can expect today. Just last July, for instance, a study from researchers in the UK found evidence that the Shingrix vaccine reduced people’s risk of dementia noticeably more than Zostavax. This finding, if further supported, would also support the idea that the herpes zoster virus is contributing to dementia.
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Source: Unique Study Is Latest to Show Shingles Vaccine Can Help Prevent Dementia
Robin Edgar
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