Childhood obesity and dental caries: an ecological investigation of the shape and moderators of the association.

BACKGROUND: Despite sharing a common risk factor in dietary sugars, the association between obesity and dental caries remains unclear. We investigated the association between obesity and dental caries in young children in England in an ecological study. METHODS: We analysed data from 326 lower tier English local authorities. Data on obesity and dental caries were retrieved from 2014/15 to 2016/17 National Child Measurement Programme and 2016/17 National Dental Epidemiology Programme. We used fractional polynomial models to explore the shape of the association between obesity and dental caries. We also examined the modifying effect of deprivation, lone parenthood, ethnicity, and fluoridation. RESULTS: Best fitting second order fractional polynomial models did not provide better fit than the linear models for the association between obesity and prevalence and severity of dental caries; therefore, the linear model was found suitable. Despite significant association, after adjusting for the effect of deprivation, obesity was neither associated with prevalence (coefficient = 0.2, 95% CI - 0.71, 0.75), nor with severity (coefficient = 0.001, 95% CI - 0.03, 0.03) of dental caries. In fully adjusted models, the proportion of white ethnicity and being in fluoridated areas were associated with a decrease in dental caries. The association between obesity and dental caries was moderated by the effect of deprivation, white ethnicity, and lone parenthood. CONCLUSIONS: The association between obesity and dental caries was linear and moderated by some demographic factors. Consequently, interventions that reduce obesity and dental caries may have a greater impact on specific groups of the population.