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Intelligence quotient in children with dental fluorosis in rural areas of Paraíba
Introduction:
Concerns about possible neurotoxicity related to fluoride exposure remain controversial, and evidence is heterogeneous across exposure ranges and study settings. This study evaluated the association between dental fluorosis and intelligence quotient (IQ) among children living in rural areas of Paraíba, Brazil.
Methods:
A nested case-control study was conducted within a cross-sectional survey. Participants were matched 1:1 by age and sex. IQ was assessed using Raven's Colored Progressive Matrices and dichotomized as Lower IQ (Levels IV-V) versus Higher IQ (Levels I-III). Dental caries (DMFT/dmft) and fluorosis (TF index) were assessed after cleaning and drying. Fluoride concentration in drinking water was determined using a fluoride ion-specific electrode. Associations with Lower IQ were tested using conditional logistic regression in the matched sample (n=136) and a sensitivity analysis using logistic regression with cluster-robust standard errors.
Results:
In crude matched analyses (68 pairs; n = 136), low family income was associated with Lower IQ (OR = 3.50, 95% CI: 1.15-10.63; p = 0.027), while dental caries showed a borderline association (OR = 1.85, 95% CI: 0.94-3.63; p = 0.075). In the adjusted conditional logistic regression model, associations were not statistically significant (income: adjusted OR = 2.93, 95% CI: 0.89-9.58; p = 0.076; caries: adjusted OR = 1.32, 95% CI: 0.57-3.05; p = 0.514), and dental fluorosis (TF>0) was not associated with Lower IQ (adjusted OR = 1.02, 95% CI: 0.45-2.33; p = 0.965). In the sensitivity analysis using the full analytic sample (n = 175) with cluster-robust standard errors clustered at the school level, low income (adjusted OR = 2.64, 95% CI: 1.04-6.71; p = 0.0416) and dental caries (adjusted OR = 2.13, 95% CI: 1.20-3.78; p = 0.0096) were associated with Lower IQ, whereas dental fluorosis was not (adjusted OR = 0.89, 95% CI: 0.55-1.45; p = 0.6471).
Conclusion:
Socioeconomic disadvantage and dental caries showed the most consistent associations with Lower IQ, whereas dental fluorosis, used as an indirect marker of earlier fluoride exposure during tooth development, was not independently associated with IQ status after adjustment when comparing Lower IQ versus Higher IQ.
