Impact of Long-Term Statin Therapy on Influenza Incidence and Overall Mortality: A Real-World Data Analysis

Background/Objectives: The study’s goal is to assess the association between long-term statin therapy and influenza incidence, influenza severity, and all-cause mortality. Methods: Two population-based dynamic cohorts (exposed and unexposed to statins) were followed from 2010 to 2019. Participants were 60 years or older; frail patients were excluded. The primary outcomes were influenza incidence, influenza-related intensive care unit (ICU) admission as a proxy for severity, and all-cause mortality. The exposed cohort comprised new statin users with a minimum of two pharmacy invoices within 90 days of enrollment. Adjusted risk ratios (aRRs) for influenza incidence, ICU admission, and mortality rate were calculated using Poisson regression. Results: The initial study population of 639,564 individuals was evenly split into exposed (319,782) and unexposed (319,782) cohorts; mean age was 71 years (standard deviation: 8 years), and 57% were women. Compared to non-users, new statin users showed a higher influenza incidence [9.39 (95% confidence interval: 9.36–9.42) vs. 7.64 (7.61–7.66) per 1000 person-years], ICU admission [1.65 (1.65–1.66) vs. 1.36 (1.35–1.36) per 1000 person-years], and overall mortality rate [97.09 (96.75–97.43) vs. 94.15 (93.82–94.47) per 1000 person-years]. Adjusted analysis revealed no significant association between statin use and influenza incidence [aRR: 1.04 (0.98–1.10)] or influenza-related ICU admission [aRR: 1.03 (0.89–1.19)] and shifted the effect on mortality from harmful to beneficial [aRR: 0.88 (0.87–0.89)]. Conclusions: Despite new users’ greater vulnerability at the start of treatment, our findings indicate that statins do not influence influenza incidence or severity but reduce all-cause mortality, warranting further exploration of their anti-inflammatory properties.