Influenza vaccination reduces dementia in patients with chronic obstructive pulmonary disease: a nationwide cohort study

This study aimed to explore the protective potential of influenza vaccination against occurrence of dementia in patients with chronic obstructive pulmonary disease (COPD), who are expected to be more vulnerable to influenza infection. This nationwide retrospective cohort study enrolled patients with COPD (aged ≥60 years) from 1 January 2001 to 31 December 2012 by using the Taiwan National Health Insurance Research Database. By applying time-dependent Cox proportional hazard model, we used multivariate analysis to calculate the adjusted HR (aHR) with 95% CI of dementia in relation to influenza vaccination among patients with COPD. Besides, patients were partitioned into four groups according to the vaccination number (unvaccinated, 1, 2-3 and ≥4 total vaccinations) to investigate the dose-response effect of vaccinations on the dementia incidence. This cohort study included 19 848 patients with COPD, and 45% of them received influenza vaccination. The aHR of dementia was 0.68 (95% CI: 0.62 to 0.74, p<0.001) comparing vaccinated patients with unvaccinated ones. Furthermore, there was a trend of dementia risk reduction with the vaccination number. For patients who received 2-3 vaccinations, the aHR was 0.81 (95% CI: 0.73 to 0.90), and for those received 4 vaccinations, the aHR was 0.44 (95% CI: 0.40 to 0.50), with p for trend <0.001. In conclusion, annual influenza vaccination can reduce the risk of dementia in patient with COPD in a dose-dependent manner.