Associations of household income and parental education with early childhood caries: the Japan Environment and Children's Study.

BACKGROUND: Although the prevalence of early childhood caries (ECC) has declined over the past few decades, it remains a significant public health concern in Japan. Socioeconomic disparities in ECC risk have been reported; however, the extent to which these disparities exist across different indicators of socioeconomic status (SES) and the degree to which early oral health practices help explain them remain unclear. This study evaluated the association between parental SES and ECC and examined the extent to which early oral health behaviors contributed to these associations.

METHODS: We analyzed the data from 68,312 children and their parents participating in the Japan Environment and Children's Study, a nationwide birth cohort recruited between 2011 and 2014. Parental SES, including household income equivalized using the OECD-modified equivalence scale and educational attainment, was assessed using self-reported questionnaires. Diagnoses of dental caries from birth to age 4 years were reported retrospectively by caregivers when the child was 4 years old. Multivariable logistic regression was used to examine associations between SES and ECC. Mediation analyses were conducted to evaluate whether oral health behaviors at age 2, including fluoride application, tooth brushing practices, continued bottle feeding, and frequency of between-meal snacks, mediated these associations. All models were adjusted for demographic and potential confounding factors.

RESULTS: Overall, 23.0% of children had been diagnosed with caries by age 4 years. The higher prevalence was consistently observed among children from lower SES backgrounds starting at around age 2 years. Both lower household income and lower parental educational attainment were associated with higher odds of ECC. The highest odds were observed among children whose parents had secondary-level education (adjusted odds ratio: 1.52; 95% confidence interval: 1.44-1.59). Although oral health behaviors mediated these associations, each behavior accounted for less than 5% of the total effect.

CONCLUSION: Lower household income and parental educational attainment were consistently associated with a higher risk of ECC from early childhood. Mediation analyses using oral health behaviors assessed at age 2 indicated that these behaviors explained a small proportion of the observed socioeconomic disparities, suggesting a small contribution of individual behaviors to early-life socioeconomic inequalities in ECC.