Project Leader Yumiko Imai of the National Institute of Biomedical Innovation, Health and Nutrition (NIBIOHN) and her colleagues performed a large-scale analysis of COVID-19 sequelae using electronic medical records of approximately 120,000 cases and revealed the incidence trends based on age and vaccination rate. Approximately 10% of sequelae, including headache, malaise, and taste and smell disorders that originated in the acute phase persisted in the post-COVID-19 period. Meanwhile, the rates of depression and disuse syndrome (various symptoms resulting from reduced activity) that persisted in the post-COVID-19 period were as high as 20-50% in the older age group. Further, the level of required nursing care tended to increase after the onset of COVID-19 in adults aged 60 and above. The study was published in the JMA Journal, the scientific journal of the Japan Medical Association and the Japanese Association of Medical Sciences.
The research group collected electronic medical record data of 122,045 inpatients and outpatients at the Tokushukai Group hospitals and clinics who were diagnosed with COVID-19 between January 1, 2020 and June 30, 2022. The data were analyzed for three study periods based on different COVID-19 strains and vaccination rates.
As a result, among patients who experienced headache, malaise, and taste and smell disorders in the acute phase (within two weeks of a COVID-19 diagnosis), approximately 1 in 10 patients had prolonged symptoms in the post-COVID-19 period. Especially in older adults aged 60 and above, depression and disuse syndrome persisted in the post-COVID-19 period in 2-5 out of 10 patients. While depression and disuse syndrome were observed to a greater extent in older patient groups, malaise/fatigue, and taste and smell disorders were observed to a greater extent in adults aged 20-50.
Compared with Period 1 (when the original and Alpha variants were dominant), Period 2 (Delta variant) and Period 3 (Omicron variant) had significantly lower incidence rates of sequelae. A difference in vaccination rates in the three study periods might have affected the incidence rates of sequelae.
Although the incidence rates of sequelae—ranging from less than 1% to approximately 3% overall—seems low when compared to the rates reported previously in questionnaire surveys targeting a few dozen to several hundred patients, the results of the current study, based on physicians' diagnoses, are considered to better reflect reality.
Imai stated, "We are now willing to develop a system that predicts the clinical course of viral infection including its sequelae by building an AI model based on large-scale clinical data."
Publication: JMA Journal
Title: Post-Coronavirus Disease 2019 Syndrome in Japan: An Observational Study Using a Medical Database
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