Assessing the impact of COVID-19 pandemic on ambulance transports for self-harm: a population-based study in Osaka Prefecture, Japan

Objectives The COVID-19 pandemic might have affected emergency medical services transports for self-harm in Japan. However, the available data are insufficient to fully understand the pandemic's impact on ambulance transports due to self-harm. This study aimed to investigate the change in the incidence of ambulance transports for self-harm from 2018 to 2021 and to identify vulnerable age groups during the pandemic.Design A population-based observational study using a database from the Osaka Prefectural Government.Setting The database covers the entire area of Osaka Prefecture and included information on ambulance transports and hospital details.Participants Ambulance transport of patients due to self-harm from 2018 through 2021 was investigated.Primary outcome measures The primary outcome was the incidence of ambulance transport for self-harm.Results We analysed 10 843 patients. Their median age was 38 years, and 69.0% were female. We observed an increasing trend of the incidence rate in cases per 100 000 population per year from 29.4 in 2018 to 31.2 in 2021. However, after adjusting for age group, sex and month, there was no difference in the incidence of ambulance transport due to self-harm in 2019 (adjusted incidence rate ratio (aIRR) 1.007; 95% CI 0.955 to 1.063), 2020 (aIRR 1.041; 95% CI 0.987 to 1.098) and 2021 (aIRR 1.022; 95% CI 0.968 to 1.078), compared with 2018. We observed no difference in 21-day mortality from 2018 through 2021. In the age group of 20-29 years, despite no difference in 2019 compared with 2018, we found an 11.7% increase in the incidence of ambulance transport due to self-harm in 2020 (aIRR 1.117; 95% CI 1.002 to 1.245) and no difference in 2021.Conclusions There was no difference in the incidence of ambulance transport due to self-harm and 21-day mortality from 2018 through 2021. However, the incidence rate of ambulance transport due to self-harm in 2020 increased in the age group of 20-29 years.