The Burden of Seasonal Influenza and Its Potential Complications Among Older Japanese Adults: A Real‐World Database Study

BACKGROUND: Seasonal influenza may lead to severe complications, including respiratory and cardiovascular disease, that result in considerable healthcare resource utilization (HCRU) and mortality, particularly in older individuals. This real-world study assessed the burden of influenza and its potential complications in older Japanese adults. METHODS: This retrospective claims database analysis (April 2015 to June 2019) included insured individuals aged ≥ 60 years at the start of four consecutive influenza seasons in Japan (October 1 to April 30). The primary endpoint was the incidence of influenza-related emergency room (ER) and outpatient visits, the incidence of hospitalizations, the probability of 30-day inpatient mortality, and 60-day medical costs of influenza or its potential complications. RESULTS: Of 8,974,708 individuals (43.2% male, mean ± standard deviation age 73.8 ± 8.9 years), 370,430 (4.13%) were diagnosed with influenza. Overall, 17.18 (95% confidence interval [CI] 16.32-18.04) and 3893.53 (3880.87-3906.19) per 100,000 individuals had influenza-related ER and outpatient visits, respectively, and 181.50 (178.71-184.28) per 100,000 individuals were hospitalized for influenza. The incidence of influenza-related ER visits and hospitalizations for influenza or potential complications and the probability of 30-day inpatient mortality increased with age. CONCLUSIONS: Seasonal influenza and its potential complications represent a substantial burden that increases with age in Japanese individuals.