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. 2024 Nov;18(11):e70032.
doi: 10.1111/irv.70032.

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

Takeshi Arashiro  1 , Yuki Tajima  2 , Yohei Ban  3 , Matthew M Loiacono  4 , Masayo Ideguchi  5 , Caroline de Courville  6
Affiliations

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

Takeshi Arashiro et al. Influenza Other Respir Viruses. 2024 Nov.

Abstract

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.

Keywords: Japan; aged; healthcare costs; hospitalization; human; influenza; mortality.

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Conflict of interest statement

All named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship, take responsibility for the integrity of the work as a whole, and have given their approval for this version to be published.

Takeshi Arashiro is a cooperative researcher with the National Institute of Infectious Diseases, Japan, and is an employee of Sanofi K.K. Yuki Tajima is an employee of Sanofi K.K. Yohei Ban has received consultancy fees from Sanofi K.K. and is an employee of Intage Healthcare Inc. Masayo Ideguchi is a full‐time employee of Sanofi K.K. and holds stock and/or stock options in the company. Matthew M Loiacono and Caroline de Courville are full‐time employees of Sanofi and hold stock and/or stock options in the company.

Figures

FIGURE 1
FIGURE 1
Study population flow. †Individuals who were diagnosed with influenza (defined as International Classification of Disease–10th revision diagnostic codes J09–J11; excluding suspected influenza) before the start of each influenza season or were prescribed an anti‐influenza drug during the same period.
FIGURE 2
FIGURE 2
Probability of mortality within 30, 60, or 90 days of influenza onset among individuals with mortality data and influenza diagnosis. †Defined as International Classification of Disease–10th revision diagnostic codes J09–J11. ‡Sensitivity analysis. CI, confidence interval.
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