Exploratory analysis of regional factors influencing early childhood caries status in 5-year-old children: evidence from national oral health surveys of China, 2005–2015

BACKGROUND: Currently, regional disparities of early childhood caries (ECC) remained underexplored. This study aimed to investigate the associations of regional factors with temporal variations of ECC among 5-year-old children in China using data from the 3rd National Oral Health Survey of China (the 2005 survey) and the 4th National Oral Health Survey of China (the 2015 survey). METHODS: Post-stratification-weighted data combining the two rounds of cross-sectional National Oral Health Surveys were used for establishing negative binomial regression models, with the number of decayed, missing and filled deciduous teeth (dmft) served as the outcome variable. Regional factors, including geographic region, per capita Gross Domestic Product (GDP), proportion of public health expenditure, dentists per million population, economic Gini coefficient and health Gini coefficient, were enrolled as explanatory variables. At individual level, sociodemographic characteristics, early childhood factors, oral health behaviors and parent-reported oral health status were added to the regression models as covariates. Sensitivity analyses were conducted on those whose mother finished the questionnaires. RESULTS: The study sample included a total of 24,014 study participants (11,099 in the 2005 survey and 12,915 in the 2015 survey). Analysis revealed that in the 2005 survey, children in northeastern China showed significantly worse dental caries status compared to western regions, while provinces with higher GDP per capita values exhibited slightly poorer dental caries outcomes. In the 2015 survey, both northeastern and eastern regions demonstrated significantly higher childhood caries prevalence than western regions, with a positive correlation remaining in public health expenditure ratio and income Gini coefficient with caries status. Analyses of pooled survey data exhibited disparities between survey years, while geographic region and GDP per capita maintained statistical significance. Sensitivity analysis showed consistent trends. CONCLUSION: Dental caries of 5-year-old children in China was associated with regional factors such as geographic location, GDP per capita, public health expenditure ratio and income Gini coefficient under certain circumstances, highlighting the need for regionally differentiated policy-making and more balanced public health resource allocation in comprehensive ECC prevention.