Long COVID among the first three waves of COVID-19 in Japan: a multicentre cohort study

Objectives Severe acute respiratory syndrome coronavirus 2 significantly impacts Japan with a high number of infections and deaths reported. Long coronavirus disease (COVID) characterised by persistent symptoms after COVID-19 has gained recognition but varies across studies. This study aimed to investigate the differences in long COVID among patients hospitalised during Japan's first three waves of the pandemic. Design Multicentre prospective cohort study. Setting 26 medical facilities across Japan between February 2020 and February 2021. Participants In total, 1066 hospitalised patients diagnosed with COVID-19 were included with 206, 301 and 559 patients in the first, second and third waves, respectively. Data were collected using electronic data capture and patient-reported outcome forms. Primary and secondary outcome measures Long COVID was assessed at 3, 6 and 12 months after COVID-19 diagnosis. Results Significant differences were observed between the waves in various baseline and clinical characteristics such as age, body mass index (BMI), comorbidities, the severity of COVID-19, complications and treatment during hospitalisation. Long COVID, particularly dyspnoea, was most prevalent in the first wave. Multivariate logistic regression analysis confirmed a significant positive association between the first wave and long COVID including dyspnoea after adjusting for age, sex, BMI, smoking status and COVID-19 severity. Conclusions Patients hospitalised during the first wave had a higher risk of experiencing long COVID, especially dyspnoea, than those hospitalised during the other waves. These findings underscore the need for continued monitoring and managing long COVID in COVID-19 survivors, particularly in those hospitalised during the first wave. Trial registration number UMIN000042299.