Dementia is a non-curable neurodegenerative disorder that poses a major global health challenge. Its number is projected to triple in the next 40 years with its associated cost to rise accordingly. Currently, available treatment is limited to drug therapy showing little to modest benefits on patient outcomes. The development of new drugs is slow despite extensive scientific effort and investments on clinical trials. Thus, in response to the lack of effective intervention, a major focus has been placed towards the identification of modifiable risk factors as targets for prevention. In the recent decades, mounting evidence has indicated a potential link between infection and dementia. More recently, several studies have reported that vaccines for common infections, such as flu, may prove effective in preventing disease onset, positioning immunization as a potential strategy for prevention. However, these studies have several limitations and are relatively small-scale. Using a large population-based database and applying state-of-the-art methods, we aim to assess the relationship between common vaccines provided among adults ≥50 years and the development of dementia. Findings can inform future clinical trials, as well as critical stakeholders including health policymakers, clinicians and individuals at risk. If results are promising, we expect that the use of an already available and routinely administered intervention will be cost-effective in reducing the burden of dementia globally.
Given the ageing population and the lack of effective treatment, the prevalence of dementia is projected to rise tremendously in the upcoming years. Nevertheless, a growing evidence has pointed towards the potential benefits of routinely administered vaccines, such as the influenza and pneumococcal vaccine, in reducing the risk of incident dementia. However, previous studies have several methodological shortcomings, rendering study findings difficult to interpret. Thus, future large-scale population-based studies are warranted to confirm the effectiveness of common vaccines in reducing dementia incidence.
Our hypothesis is that exposure to common vaccines, including the vaccine for influenza, pneumonia, shingles, and tetanus, diphtheria and pertussis (TDP), is associated with a lower risk of dementia. To investigate this potential association, we will conduct a cohort study with a nested case-control analysis. We will assemble a cohort of individuals at least 50 years of age between 1 January 1988 and 31 December 2018 and whom will be followed until 31 March 2021. Within this cohort, each dementia case will be matched with up to 40 dementia-free controls on sex, age, cohort entry, and duration of follow-up. Conditional logistic regression will be used to compute odds ratios (OR) and 95% confidence intervals (CI) to estimate the risk of dementia in the vaccinated group, compared with the unvaccinated group. In secondary analyses, we will assess the risk of dementia, stratified based on 1) the individual vaccine, 2) time since first immunization and 3) history of past immunization, age, sex, and socioeconomic status. Finally, we will conduct several sensitivity and ancillary analyses to assess the robustness of our results. Ultimately, we hope the findings from this large population-based study will inform future research and help develop novel strategies to reduce the widespread burden of dementia.
The primary outcome of interest is incident diagnosis of dementia, as identified by Read codes (listed in Appendix 1).
Samy Suissa - Chief Investigator - Sir Mortimer B Davis Jewish General Hospital
Paul Brassard - Corresponding Applicant - McGill University
Antonios Douros - Collaborator - McGill University
Zharmaine Ante - Collaborator - Sir Mortimer B Davis Jewish General Hospital
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