General characteristics of participants.

The relationship between individuals’ socioeconomic characteristics and their health outcomes is widely acknowledged. However, the specific mechanisms through which these factors are interconnected have not been studied sufficiently. The current study investigated the association among socio-economic status (education of parents, economic status of family) and perceived health mediated by physical activity and sedentary time (purpose for study or not), before and during Covid-19. Three cross-sectional and population-based representative surveys from 2019, 2020, and 2021 were utilized. Overall, 167,099 Korean adolescents (57,303 in 2019, 54,948 in 2020, 54,848 in 2021) participated. A multi-group structural equation model showed that socio-economic status was associated with perceived health through physical activity and sedentary behaviors. Both measures of socio-economic status were positively associated with sedentary time for study purposes, but negatively associated with purposes other than study. Higher education of parents negatively predicted physical activity, whereas higher economic status of family positively predicted physical activity. The impact of socio-economic status on sedentary time tended to increase after the pandemic. Covid-19 significantly affected adolescents’ health and health-related behaviors. Comprehensive policies considering adolescents’ socio-economic status and their physical activity and sedentary time would mitigate the health effects of the pandemic.