a nationwide, multilevel, register-based, repeated cross-sectional study
Objectives: This study examines the geographic variation and trends in the distribution of dental caries among adolescents in Danish municipalities between 1995 and 2013. Moreover, the study explores the trends in the association between childhood socioeconomic position (SEP) and dental caries experience between 1995 and 2013. Methods: Nationwide repeated cross-sectional studies were conducted on 15-year-olds in Denmark from 1995 (n=49173), 2003 (n=50512), and 2013 (n=51214). Data on the outcome, dental caries experience (represented by the decayed, missing, and filled surfaces [DMFS] index), were obtained from the national dental register of the Danish Health Authority. Data on individual-level social variables (childhood SEP, immigration status, country of origin, number of children and persons in the family, and household type) were obtained from administrative registers at Statistics Denmark. Municipality deprivation data (GINI coefficient; proportion of poor, unemployed, low educated, and unmarried/non-cohabiting individuals; proportion of household overcrowding and single parent households) were obtained from Statistics Denmark’s Statbank (Statistikbanken). Measures of childhood SEP included previous year’s parental education, occupational social class, and household equivalized disposable income. Geo-mapping of trends in dental caries experience was undertaken for the 275 Danish municipalities. Multilevel Bayesian conditional autoregressive models with the zero-inflated negative binomial (ZINB) distribution as the outcome distribution were used to evaluate the association between childhood SEP and dental caries experience, hierarchically adjusting for individual and contextual covariates, while also assessing the spatial autocorrelation between neighboring municipalities using a neighborhood adjacency matrix.Findings-to-date: Caries prevalence among Danish adolescents declined from 71% in 1995 to 63% in 2003 and 45% in 2013. In single-level multivariable ZINB models, in all three years, clear gradients were observed in terms of caries differentials in all three SEP categories, with statistically significant associations (Type 3 p values, <0.0001). In unadjusted analyses, considerable variation in dental caries experience across the municipalities was observed.