# A cross-sectional study investigating the association between parental daily brushing, extended breastfeeding, or parental smoking habit and early childhood dental caries in 4-year-old children: the Japan Environment and Children’s Study

## TL;DR

This study found that irregular brushing, extended breastfeeding, and parental smoking increase the risk of tooth decay in 4-year-old children.

## Contribution

The study identifies specific parental behaviors linked to early childhood dental caries using a large national cohort.

## Key findings

- Occasional parental brushing increases ECC risk compared to routine brushing.
- Extended breastfeeding is strongly associated with higher ECC odds.
- Parental smoking, especially by mothers, significantly raises ECC risk.

## Abstract

Dental caries is estimated to affect almost half of preschool children worldwide and is associated with low academic performance in school age and poor health in adulthood. Thus, the prevention of dental caries is an important issue that must be addressed. The objective of this study was to clarify the factors associated with early childhood dental caries (ECC) in 4-year-old children.

This study was part of an ongoing nationwide cohort study; the Japan Environment and Children’s Study. Approximately 100,000 expectant mothers were recruited from 15 Regional Centers between January 2011 and March 2014. Questionnaires were regularly administered to participating mothers. Data on the presence of ECC at 4 years of age, frequency of parental brushing, continuation of breastfeeding, parental smoking habits, and other factors considered to be related with development of ECC were obtained from the datasets released in October 2019 and April 2021. Then, the data were statistically analyzed.

After excluding 25,990 cases due to missing data referring to the prevalence of ECC, 74,310 cases were analyzed. The logistic regression analysis revealed that occasional parental brushing (adjusted odds ratio (aOR) 1.33, 95% confidence interval (95% CI) 1.27–1.39) was associated with significantly increased odds for ECC when compared to routine parental brushing. In addition, extended breastfeeding (aOR 2.07, 95% CI 1.86–2.29), continued smoking of mothers (aOR 1.42, 95% CI 1.30–1.55), and continued smoking of fathers (aOR 1.25, 95% CI 1.20–1.31) were associated with increased odds for ECC.

Irregular parental brushing, extended breastfeeding, and parental smoking habits were found to be associated with increased odds for ECC in 4-year-old children.

The online version contains supplementary material available at 10.1186/s12887-025-05997-8.