Can someone help me understand this? How does this mean a 50% increase in dementia?
Results: Common vaccines were associated with an increased risk of dementia (OR, 1.38 [95% CI, 1.36-1.40]), compared with no exposure.
Edit: Adding Grok's feedback
The study at https://pubmed.ncbi.nlm.nih.gov/36542511/ is titled "Common Vaccines and the Risk of Incident Dementia: A Population-based Cohort Study," published in the Journal of Infectious Diseases in 2023 (PMID: 36542511). It is a large population-based cohort study (using a nested case-control design) of dementia-free adults aged ≥50 years in the UK's Clinical Practice Research Datalink, followed from 1988 to 2018.
The researchers investigated whether exposure to common vaccines (administered more than 2 years before dementia diagnosis/index date) was linked to dementia risk, compared to no exposure during the study period.
Key quantitative finding on increased dementia risk:
Common vaccines were associated with a 38% increased risk of incident dementia, with an adjusted odds ratio (OR = 1.38, 95% confidence interval [CI]: 1.36–1.40) compared to no exposure.
However, the authors emphasize that this observed increase is not causal. Sensitivity analyses showed attenuation (weakening) of the association when accounting for potential biases:
With a 10-year lag period (exposure >10 years before index date): OR = 1.20 (95% CI: 1.18–1.23), a 20% increased risk.
When using active comparators like prostate cancer screening participation: OR = 1.19 (95% CI: 1.11–1.27).
Breast cancer screening comparator did not attenuate it as much (OR = 1.37, 95% CI: 1.30–1.45).
The study's conclusion states that common vaccines were not associated with a decreased risk of dementia (contrary to some prior observational suggestions). The apparent increased risk was likely explained by unmeasured confounding (e.g., healthier people more likely to get vaccinated and screened) and detection bias (vaccinated individuals may have more healthcare contact, leading to earlier dementia diagnosis).
No hazard ratios (HRs) were directly reported in the abstract (it used ORs due to the case-control matching), and the study does not claim vaccines truly cause higher dementia rates—rather, the raw association is confounded. This contrasts with some other studies on specific vaccines (e.g., influenza or herpes zoster) that have reported protective associations against dementia.
Thank you!
Can someone help me understand this? How does this mean a 50% increase in dementia?
Edit: Adding Grok's feedback
The study at https://pubmed.ncbi.nlm.nih.gov/36542511/ is titled "Common Vaccines and the Risk of Incident Dementia: A Population-based Cohort Study," published in the Journal of Infectious Diseases in 2023 (PMID: 36542511). It is a large population-based cohort study (using a nested case-control design) of dementia-free adults aged ≥50 years in the UK's Clinical Practice Research Datalink, followed from 1988 to 2018.
The researchers investigated whether exposure to common vaccines (administered more than 2 years before dementia diagnosis/index date) was linked to dementia risk, compared to no exposure during the study period.
Key quantitative finding on increased dementia risk:
However, the authors emphasize that this observed increase is not causal. Sensitivity analyses showed attenuation (weakening) of the association when accounting for potential biases:
The study's conclusion states that common vaccines were not associated with a decreased risk of dementia (contrary to some prior observational suggestions). The apparent increased risk was likely explained by unmeasured confounding (e.g., healthier people more likely to get vaccinated and screened) and detection bias (vaccinated individuals may have more healthcare contact, leading to earlier dementia diagnosis).
No hazard ratios (HRs) were directly reported in the abstract (it used ORs due to the case-control matching), and the study does not claim vaccines truly cause higher dementia rates—rather, the raw association is confounded. This contrasts with some other studies on specific vaccines (e.g., influenza or herpes zoster) that have reported protective associations against dementia.