Objective To investigate the influence of dopamine beta-hydroxylase (DBH) gene polymorphism, iodine, fluoride, and their interaction on children's intelligence.
Methods Three schools were selected according to the history of water iodine concentration in Tianjin, and then cluster sampling was performed to select 299 children. Combined Raven's Test was used to measure the children's intelligence level; urine samples were collected and then arsenic-cerium catalytic spectrophotometry and the fluoride-ion selective electrode method were used to measure urinary iodine and fluoride levels, respectively; polymerase chain reaction-restriction fragment length polymorphism was used to determine DBH genotype.
Results The children aged (10-12) years in the high iodine area 2 had a significantly lower intelligence level than those in the high iodine area 1 and the suitable iodine area (108.24±13.69 vs 114.48±11.91/113.10±12.54, F=3.45, P < 0.05). The multivariate logistic regression analysis showed that urinary fluoride was a risk factor for intelligence impairment (OR=2.32, 95%CI: 1.09-4.95, P < 0.05). The DBH gene, urinary fluoride, and urinary iodine had no interaction with intelligence, and the DBH gene had no mediating effect on intelligence impairment induced by iodine and fluoride.
Conclusion The intelligence level of children aged (10-12) years tends to decrease in the areas where the concentration of water iodine is over 300 μg/L in Tianjin. The DBH gene, urinary fluoride, and urinary iodine have no interaction with intelligence, and the DBH gene has no mediating effect on intelligence, which requires further research.
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