Common vaccines and the risk of incident dementia: a population-based cohort study


 
 
 Observational studies suggesting that immunizations may strongly decrease the risk of dementia had several methodological limitations. Thus, we assessed whether common vaccines are associated with the risk of dementia.
 
 
 
 We assembled a population-based cohort of dementia-free individuals in the UK’s CPRD aged ≥50 years between 1988 and 2018. Using a nested case-control approach, we matched each case of dementia with four controls. Conditional logistic regression yielded confounder-adjusted odds ratios (ORs) with 95% confidence intervals (CIs) of dementia associated with common vaccines >2 years before the index date compared with no exposure during the study period. Moreover, we applied a 10-year lag period and used active comparators (participation in breast or prostate cancer screening) to account for detection bias.
 
 
 
 Common vaccines were associated with an increased risk of dementia (OR, 1.38; 95% CI, 1.36-1.40), compared with no exposure. Applying a 10-year lag period (OR, 1.20; 95% CI, 1.18-1.23) and comparing versus prostate cancer screening (OR, 1.19; 95% CI, 1.11-1.27) but not versus breast cancer screening (OR, 1.37; 95% CI, 1.30-1.45) attenuated the risk increase.
 
 
 
 Common vaccines were not associated with a decreased risk of dementia. Unmeasured confounding and detection bias likely accounted for the observed increased risk.
