Association of long-duration breastfeeding and dental caries estimated with marginal structural models.

PURPOSE: To estimate the association between breastfeeding 24 months or beyond and severe early childhood caries (S-ECC). METHODS: Within a birth cohort (n = 715) from low-income families in Porto Alegre, Brazil, the age 38-month prevalence of S-ECC (>/=4 affected tooth surfaces or >/=1 affected maxillary anterior teeth) was compared over breastfeeding duration categories using marginal structural models to account for time-dependent confounding by other feeding habits and child growth. Additional analyses assessed whether daily breastfeeding frequency modified the association of breastfeeding duration and S-ECC. Multiple imputation and censoring weights were used to address incomplete covariate information and missing outcomes, respectively. Confidence intervals (CIs) were estimated using bootstrap resampling. RESULTS: Breastfeeding 24 months or beyond was associated with the highest adjusted population-average S-ECC prevalence (0.45; 95% CI, 0.36 to 0.54) compared with breastfeeding less than 6 months (0.22; 95% CI, 0.15 to 0.28), 6-11 months (0.38; 95% CI, 0.25 to 0.53), or 12-23 months (0.39; 95% CI, 0.20 to 0.56). High-frequency breastfeeding enhanced the association between long-duration breastfeeding and caries (excess prevalence due to interaction: 0.13; 80% CI, -0.03 to 0.30). CONCLUSIONS: In this population, breastfeeding 24 months or beyond, particularly if frequent, was associated with S-ECC. Dental health should be one consideration, among many, in evaluating health outcomes associated with breastfeeding 24 months or beyond.