Researchers Look at the Risk of Dementia After Getting a Shingles Shot
Researchers looked into whether getting the herpes zoster vaccine was linked to fewer diagnoses of dementia in older people. The study looked at seniors in Ontario, Canada, who were 70 years old or older. It used policy-driven eligibility rules to create conditions that were close to random.
Researchers reduced health and behavior differences by comparing people who were born just before and just after eligibility cutoffs. This design enabled vaccination status to serve as the principal variable distinguishing groups. These natural experiments enhance causal interpretation beyond conventional observational studies.
Source: News-Medical/Website
Policy Cutoffs Created Natural Experimental Conditions
In Ontario, the shingles vaccination program was only open to people who were born on certain dates. The main cutoff date was January 1, 1946, which determined who could get the vaccine. A second cutoff date of January 1, 1945, helped with replication.
People on either side of each cutoff had similar baseline traits. The health status, demographics, and access to care seemed to be similar between the groups being compared. This similarity bolsters the hypothesis that outcome disparities indicated vaccination effects.
Electronic Health Records Enabled Long Term Follow Up
The analysis utilized electronic health records from primary care practices covering the period from 1990 to mid-2022. Researchers monitored the incidence of new dementia diagnoses following the initiation of the vaccination program. Longitudinal data facilitated the evaluation of outcomes across prolonged durations.
Survey data added to records to help estimate how many people were getting vaccinated near the eligibility thresholds. This showed that policy rules had a big effect on how many people got vaccinated. The differences in uptake confirmed the assumptions made in the experimental design.
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Fewer Dementia Diagnoses Linked to Vaccination
Over an average of 5.5 years of follow-up, eligible people were diagnosed with dementia less often. Being on the vaccinated side of eligibility was linked to a 2% drop in the absolute number. The fact that confidence intervals did not cross zero shows that the results were statistically strong.
The decrease was consistently observed across both eligibility thresholds analyzed. This consistency boosts faith in the link that was seen. The results indicated a significant impact at the population level among older adults.
Additional Comparisons Supported The Core Findings
Researchers examined dementia trends in Ontario relative to other Canadian provinces. Provinces lacking analogous vaccination programs functioned as controls. Eligible Ontario cohorts exhibited a reduction in new dementia diagnoses following the initiation of the program.
These quasi-experimental comparisons assisted in triangulating results. Variations manifested solely in contexts of vaccination accessibility. This pattern made it less likely that larger trends over time were the cause of the results.
Findings Indicate a Potential Causal Relationship
Authors construed converging results as more indicative of causality than correlation. Natural experiments and interprovincial comparisons exhibited directional alignment. Together, they made the case stronger that getting vaccinated may lower the risk of dementia.
The results surpassed the conclusions that conventional observational studies could reliably ascertain. Researchers simulated randomized exposure by manipulating policy rules. This design made the conclusions more believable.
Consequences for Neuroimmune Health and Prevention
The study suggests that shingles vaccination may prevent or postpone the onset of dementia. The authors underscored the necessity for mechanistic research investigating neuroimmune pathways. Comprehending biological mechanisms may enhance future prevention strategies.
If verified, vaccination could signify a scalable public health measure. Safeguarding older adults from infection may confer cognitive advantages. More research will show what this means for policy and medicine.
