A Reduction in the Number of Hospitalized Cases of Acute Meningitis during the COVID-19 Pandemic in Japan.

Objective The changes in the prevalence of acute meningitis during the coronavirus disease 2019 (COVID-19) pandemic remain unclear. This study aimed to compare the prevalence of acute meningitis before and during the COVID-19 pandemic in Japan. Methods We retrospectively reviewed the Japanese nationwide administrative medical payment system database, Diagnosis Procedure Combination (DPC), from 2016 to 2022. A total of 547 hospitals consistently and seamlessly offered DPC data during this period. The study period was divided into the following three periods: April 2016 to March 2018 (fiscal years 2016-2017), April 2018-March 2020 (2018-2019), and April 2020-March 2022 (2020-2021). Results Among the 28,161,806 patients hospitalized during the study period, 28,399 were hospitalized for acute meningitis: 16,678 for viral/aseptic type, 6,189 for bacterial type, 655 for fungal type, 429 for tuberculous, 2,310 for carcinomatous type, and 2,138 for other or unknown types of meningitis. A significant decrease during the pandemic was confirmed in viral (n=7,032, n=5,775, and n=3,871 in each period; p<0.0001) and bacterial meningitis (n=2,291, n=2,239, and n=1,659; p<0.0001) cases. Meanwhile, no decrease was observed in fungal meningitis (n=212, n=246, and n=197; p=0.056) or carcinomatous meningitis (n=781, n=795, and n=734; p=0.27). The decrease in the number of tuberculous meningitis cases was equivocal (n=166, n=146, and n=117; p=0.014). The decrease during the pandemic was more remarkable in younger populations aged <50 years than in older populations, both for viral and bacterial meningitis. Conclusion The number of hospitalized cases of acute meningitis clearly decreased during the COVID-19 pandemic, especially for viral and bacterial meningitis in younger populations aged <50 years.