Making use of a Welsh vaccination policy that set strict and defined eligibility criteria for receiving the herpes zoster (shingles) vaccine, researchers have found that shingles vaccination may also significantly reduce the probability of dementia. The findings were published yesterday in Nature.
Previous research has found an association between the shingles vaccine and reduced dementia risk. However, those studies could not determine whether adults who chose to get vaccinated had other fundamental differences in lifestyle or motivation than adults who did not, noted Markus Eyting, Ph.D., of Stanford University, and colleagues.
In 2013, Wales instituted a policy whereby individuals born after September 2, 1933, were progressively eligible for a live-attenuated shingles vaccine; those born before that date were never eligible. Eyting and colleagues noted that this created a “natural experiment” in which they could avoid many confounding variables present in earlier studies.
Drawing on electronic health record registries, the researchers compiled data on 282,541 adults born between September 1, 1925, and September 1, 1942, who were dementia-free prior to the rollout of the vaccine program. These naturally occurring comparison groups did not differ appreciably from each other in ways that might affect the risk for dementia.
During a follow-up period of seven years, a little more than 14,000 adults in the study sample had at least one diagnosis of shingles, while around 35,000 were newly diagnosed with dementia. After adjusting for age differences, the researchers found that adults who were eligible for the shingles vaccine had an 18.8% lower risk of a shingles diagnosis than the ineligible adults, while adults who actually received the vaccine had a 37.2% lower risk of shingles. Similarly, adults eligible for the vaccine had an 8.5% reduced risk of a dementia diagnosis during the follow-up period, while those who took the vaccine had a 20% reduced risk. Differences were seen even between individuals born weeks before or after the eligibility date. This protective effect was stronger among women than men.
The researchers replicated these findings in a larger study that combined the populations of Wales and England—which had a similar vaccine rollout initiative—and used a different variable for assessing dementia (death certificates showing death with dementia as a primary cause).
“Our substantial effect sizes, combined with the relatively low cost of the zoster vaccine, imply that, if these findings are truly causal, the zoster vaccine will be both far more effective as well as cost-effective in preventing or delaying dementia than existing pharmaceutical interventions,” Eyting and colleagues concluded.
For related information, see the Psychiatric News article “Dementia Cases Projected to Double: Clinicians, Policymakers Can Help Reduce Risk.”
(Image: Getty Images/iStock/CatLane)
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