Drug Discov Ther. 2023;17(1):60-65. (DOI: 10.5582/ddt.2022.01111)

Age distribution and disease severity of COVID-19 patients continued to change in a time-dependent manner from May 2021 to April 2022 in the regional core hospital in Japan

Kawaura F, Kishi T, Yamamoto T, Nakayama S, Goto T, Tsurusawa R, Katagiri T, Yamanouchi K, Matsuo A, Kobayashi-Watanabe N, Imamura T, Hirooka Y, Takagi K, Umemura T, Fujimoto K, Hayashi S, Takamori A

The present retrospective study aimed to examine the real-world data regarding time-dependent changes in the age distribution of patients with coronavirus disease 2019 (COVID-19) as well as the severity and infectivity in a regional core hospital in Japan. Patients with COVID-19 who visited the fever outpatient branch in Takagi Hospital during phase I (May 1 to December 31, 2021), and during phase II (January 1 to April 30, 2022) were evaluated. The age distribution of outpatients and the characteristics of inpatients aged > 75 years were compared between phases I and II. The age distribution of outpatients shifted from the older generation in phase I to the younger generation in phase II (p < 0.01). Disease severity might be reduced in a time-dependent manner with a decrease in the hospitalization rate (phase I: 145/368 (39.4%); phase II: 104/1496 (7.0%); p < 0.01) and mortality rate (phase I: 10/368 (2.7%); phase II: 7/1496 (0.5%); p < 0.01). The number of patients increased in phase II (374.0/month) compared to that in phase I (36.8/month). Regarding the older inpatients, the disease severity of COVID-19 and hospitalization days were reduced in phase II compared to those in phase I (p < 0.01, each). In conclusion, the present study suggests a change in the age distribution of patients with COVID-19, a decrease in toxicity, and an increase in infectivity of severe acute respiratory syndrome coronavirus 2 in a time-dependent manner.

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