Key findings
This study analyzed 18-year trends in subjective health and its association with demographic and behavioral factors using a nationally representative cohort of South Korean adolescents, including the COVID-19 pandemic era, and yielded several key findings. The prevalence of adolescents reporting high subjective health increased before the COVID-19 pandemic; however, this trend reversed during the early and mid-pandemic (2020–2022). Subsequently, in the late-pandemic period (2023), it slightly increased. AAPC before the COVID-19 pandemic showed consistent improvement in subjective health status, however, the decline observed during the COVID-19 pandemic in all demographic groups highlights the widespread impact of the global health crisis on perceived health. Socio-demographic factors such as female sex, low academic achievement, low household income, and obese BMI were consistently associated with a lower likelihood of reporting high subjective health. Conversely, positive behavioral factors, such as regular breakfast consumption, sufficient fruit intake, sufficient physical activity, sufficient sleep, usually brushing teeth, and low stress levels, were associated with higher subjective health. These associations became more pronounced during the pandemic, suggesting that healthy lifestyle choices may have offered resilience against its challenges.
Comparison with previous studies
Previous studies have documented the importance of a healthy lifestyle for improving and maintaining physical and mental health. However, many of these studies have been limited by relatively small sample sizes, such as those conducted in Belgium (n = 6,054)17, South Korea (n = 7,700)18, and China (n = 161,744)19, leading at times to inconclusive evidence and controversial findings. In contrast, our study utilized large, population-based national data to examine trends and associated factors in self-rated health, offering more robust and generalizable results. This approach provides a clearer understanding of the determinants of adolescent subjective health.
In comparison with previous studies, several investigations corroborate our main findings regarding the detrimental impact of the COVID-19 pandemic on subjective health across diverse populations. Specifically, a Polish study found that COVID-19 convalescents who experienced symptomatic manifestations exhibited a higher propensity for developing nervousness, tension, and anxiety compared to those with milder symptomatology, with female and younger participants demonstrating particular vulnerability to post-recovery psychological distress20 Furthermore, a longitudinal cohort investigation of older individuals in England documented a systematic deterioration in mental health and well-being, characterized by persistent socioeconomic inequities, predominantly affecting women and non-partnered people21. Moreover, research conducted in the Netherlands established that lockdown measures exerted differential impacts on individuals with chronic conditions and urban residents, resulting in diminished self-reported health status22. These investigations collectively substantiate our findings by elucidating how sociodemographic variables influenced the varying degrees of subjective health deterioration across distinct population segments during the pandemic period.
Plausible mechanisms
Before the COVID-19 pandemic, there was an increase in the percentage of adolescents reporting high subjective health, potentially due to South Korea’s economic growth. Economic growth has been associated with better nutrition, enhanced public health infrastructure, and more effective medical technology, leading to improved public health23,24. The steady increase in South Korea’s gross domestic product before the pandemic likely contributed to the rising trend in subjective health. However, the COVID-19 pandemic led to a decline in subjective health, likely due to reduced socialization opportunities from lockdowns and stay-at-home orders25. Increased consumption of substances like alcohol and tobacco during the pandemic exacerbated this decline26,27. Remote learning and increased time at home disrupted regular routines, leading to more sedentary behavior and a preference for quick, unhealthy foods over balanced meals28.
The mechanisms underlying the decline in subjective health during the pandemic can be linked to the interruption of positive health behaviors and routines. School closures and social distancing measures limited access to healthy meals and physical activity opportunities provided by schools29. Increased screen time and lack of structured schedules contributed to poor sleep hygiene and higher stress levels. The pandemic’s economic impact disproportionately affected low-income families, exacerbating existing health disparities. Additionally, the social isolation resulting from lockdowns had a profound effect on mental health, particularly among adolescents who rely heavily on peer interactions for emotional support30.
According to previous research, significant gender differences have been observed in physical activity, with males more frequently meeting the World Health Organization’s guidelines, which recommend engaging in at least 60 min of moderate-to-vigorous physical activity daily31. Adequate physical activity is strongly associated with lower stress levels and a healthier BMI, which may help explain the consistently lower subjective health reported among adolescent females compared to males32,33.
Understanding these mechanisms is crucial for developing comprehensive policies that address both immediate and long-term health challenges adolescents face. School-based nutritional programs, mental health services, physical activity promotion, and economic policies supporting low-income families are necessary to mitigate the adverse effects of such crises34. Furthermore, the lower odds of females reporting high subjective health, further reduced by the pandemic, suggest a need for sex-specific health interventions to address the unique challenges faced by female adolescents.
Policy implications
Adolescence is a critical stage marked by significant physical and psychological changes, necessitating efforts to promote mental health and well-being35. The decline in subjective health among adolescents during the COVID-19 pandemic is alarming, requiring targeted policies to restore previous levels of subjective health, particularly for those with vulnerable demographics36. Key recommendations include implementing school-based nutritional programs that provide healthy meals, promoting oral hygiene, encouraging physical activity through school and community initiatives, enhancing access to mental health services and stress management programs, promoting good sleep hygiene, and providing additional educational support such as tutoring and mentoring to improve academic performance and health perceptions16,37.
Strengths and limitations
This study has multiple strengths. First, we used large-scale, population-based, nationwide data on adolescents to examine trends in subjective health before and during the COVID-19 pandemic. Second, despite the challenges of collecting individual data during the COVID-19 pandemic, our analysis was based on data gathered through non-face-to-face methods unaffected by the COVID-19 pandemic. Third, unlike objective health, subjective health encompasses unquantified aspects of well-being, thereby broadening the scope of research.
However, this study has several limitations. First, the data were collected only from the South Korean adolescent population, so the findings may not apply to other regions of the world due to cultural differences and variations in countries’ responses to the COVID-19 pandemic. Large-scale international research is required to find global associations between adolescents’ subjective health and the COVID-19 pandemic. Second, because only adolescents attending school were allowed to participate, the sample might not represent all Korean youth between the ages of 12 and 18 years. However, only approximately 1.8% of those between the ages of 12 and 18 do not attend school in Korea. Third, a self-report questionnaire was used to collect information about adolescents’ subjective health, which may underestimate the prevalence of these issues due to reporting bias38.
