Fluoridated Water Modifies the Effect of Breastfeeding on Dental Caries

Breastfeeding is important for health and development. Yet, the interaction between breastfeeding duration and usage of fluoridated water on caries experience has not been investigated. This study examined exposure to fluoridation as an effect modifier of the association between breastfeeding duration and caries. The 2012 to 2014 national population-based study of Australian children involved parental questionnaires and oral epidemiological assessment. Children were grouped by parent-reported breastfeeding duration into minimal (none or <1 mo), breastfed for 1 to <6 mo, breastfed for 6 to 24 mo, and sustained (>24 mo). Residential history and main water source used for the first 2 y of life were collected to group children into exposed (WF) and nonexposed (NF) to fluoridation. Socioeconomic status, infant formula feeding, and sugar-sweetened beverage (SSB) consumption data were collected. The prevalence and severity of caries in children aged 5 to 6 y were primary outcomes. Multivariable regression models with robust error estimation were generated to compute prevalence ratios (PRs) and mean ratios (MRs) for 3 breastfeeding groups against the reference (breastfed for 6-24 mo). Of the 5- to 6-y-old children, 2,721 were in the WF and 1,737 were in the NF groups. The groups had comparable distributions of socioeconomic factors, infant formula feeding, and SSB consumption. There were U-shape distributions of caries experience among breastfeeding groups, being more pronounced among NF children. Among NF children, the minimal and sustained breastfeeding groups had significantly higher PR (1.4 [1.1-1.9] and 1.8 [1.4-2.4]) and MR (2.1 [1.4-3.3] and 2.4 [1.4-4.1]) than the reference group. However, among the WF children, this association between breastfeeding duration and caries attenuated after adjustment for other factors. The study contributes evidence of a nonlinear (U-shape) association between breastfeeding duration and dental caries. Early life exposure to fluoridated drinking water attenuated the potential cariogenic effect of both lack of and sustained breastfeeding.