Abstract
BACKGROUND: Childhood obesity has increased markedly in Thailand, yet nationwide data on clinical outcomes, and the impact of the COVID-19 pandemic remain limited, particularly form Southeast Asia. We examined nationwide trends in hospital-based obesity prevalence, associated comorbidities, and mortality among hospitalized Thai children from 2015 to 2023, with specific focus on pandemic-related changes. METHODS: We conducted a retrospective analysis of all pediatric hospital admissions using National Health Security Office data. The study period covered from 2015 to 2023, including hospitalized children aged 1 month to < 18 years. The study period was stratified into pre-pandemic, pandemic, and post-pandemic phases. Obesity was defined using ICD-10-TM diagnosis codes. We used logistic regression to quantify associations between obesity and comorbidities and Cox proportional hazards models to examine mortality risk factors. Standard errors were adjusted for clustering at the hospital level. RESULTS: Among 14,483,566 hospitalized children, 42,168 included an obesity diagnosis, yielding an overall prevalence of 29.1 (95% CI: 28.8–29.4) per 10,000 hospitalized children. Obesity prevalence more than doubled during the pandemic, rising from 20.1 per 10,000 pre-pandemic to 45.3 per 10,000 during and remaining elevated at 45.5 per 10,000 post-pandemic. Children with obesity exhibited significantly increased odds of serious comorbidities, with the highest associations observed for nonalcoholic fatty liver disease (NAFLD) (adjusted OR 223.67, 95% CI 121.22–412.71) and orthopedic conditions (adjusted OR 117.59; 95% CI 66.82–206.93). The pandemic period was associated with divergent trends in comorbidity patterns: metabolic complications increased, with type 2 diabetes rising 28% (combined OR 1.28, 95% CI 1.09–1.52) and NAFLD increasing 64% post-pandemic (OR 1.64, 95% CI 1.54–1.75), while conditions requiring routine screening showed apparent decreases during pandemic, including documented obstructive sleep apnea (OR 0.55, 95% CI 0.42–0.71) and metabolic syndrome (post-pandemic OR 0.37, 95% CI 0.31–0.45). In-hospital mortality among children with obesity was 4.7 per 1,000 children. Cardiovascular comorbidities conferred the highest mortality risk (adjusted HR 5.86, 95% CI 3.57–9.61). CONCLUSION: Childhood obesity among hospitalized children in Thailand increased sharply during the COVID-19 pandemic and remained elevated through 2023. Obesity was strongly associated with metabolic and orthopedic complications, and indicators of glycemic dysregulation worsen during the pandemic. These findings support strengthening pediatric obesity prevention and implementing systematic screening programs and risk stratification to inform service planning and clinical guidance in Thailand and potentially across Southeast Asia. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12889-026-26570-7.