A Shingles Vaccine Policy Paved Way for a Stunning Find

In late 2013, Wales changed its shingles vaccine policy: Those people born on or after Sept. 2, 1933, could receive the Zostavax shot; those born before that date could not. The Guardian reports it "created a natural experiment," and one that researchers say now indicates the vaccine does reduce the risk of developing dementia—by 20%. Researchers delved into the health records of more than 280,000 adults who fell on either side of the birthday cutoff, which the New York Times reports was imposed due to limited stocks of the vaccine and because it was believed to not be as effective in people over 80. Yet "individuals born just 1 week before 2 September 1933 are unlikely to differ systematically from those born 1 week later," the authors wrote.

After adjusting for the fact that there wasn't a 100% participation rate among those eligible to get the vaccine, the researchers determined those who were vaccinated had a 20% lower risk of being diagnosed with dementia over the next seven years compared to the camp that did not get the shot. The effect was strongest among women. The Guardian reports the study, published in Nature, follows previous indications that shingles vaccines could have this effect, with Oxford researchers last year observing an even bigger impact among those who took the newer Shingrix (Zostavax has been largely discontinued in favor of the longer-lasting Shingrix, per the Times); researchers say this study shows more of a direct link.

As for why the vaccine could be having the impact, the Guardian shares theories: that it cuts down on inflammation in the nervous system by preventing the virus that causes chickenpox in children from reactivating, or that it causes "broader" changes in the immune system that offer increased protection. Either way, as one shingles researcher puts it to the Times, "If you're reducing the risk of dementia by 20%, that's quite important in a public health context, given that we don't really have much else at the moment that slows down the onset of dementia." (More discoveries stories.)