A study on children's intelligence difference with different iodine concentration in drinking water and its influencing factors in Tianjin

Objective To explore the effect of high iodine and other factors on children's intelligence. Methods A total of 399 children aged 7-12 years were randomly selected from the iodine-excess endemial area (water iodine>300 μg/L), iodine-excess area (150-300 μg/L) and non iodine-excess area (water iodine ≤ 100 μg/L). Questionnaire survey was used to collect the general situation of the population and the potential influencing factors of intelligence. Urine samples were tested for urinary iodine and urinary fluoride, and the combined Raven's test for rural China (CRT-RC) was used for intelligence test. Results The level of intelligence quotient (IQ) of 10-12 years old children in the iodine-excess endemial area(107.55±13.81) was significantly lower than that in the iodine-excess area (113.14±10.97) (P=0.019), and the distribulation of IQ was different from that in the control area(P=0.012).The ability of perceived distinguish ability, similarity ability, comparative reasoning ability, series relationship ability and abstract reasoning ability of children aged 10-12 years in the iodine-excess endemial area were lower than those of iodine-excess and non iodine-excess area(all P<0.05). Multivariate Logistic analysis showed that age was a risk factor for intellectual impairment(OR=1.590, 95% CI:1.273-1.986, P<0.001). Conclusion The intelligence level of children aged 10-12 in Tianjin in iodine-excess endemial area decreased. The relationship between iodine and children's intelligence was not found, and further study was needed.