Effect of iodine excess on intelligence development in 8～10 years old pupils

Objective To explore the effect of iodine excess (IE) on the intelligence development and mental retardation of pupils compared with those living in the areas of adequate iodine intake from dringking water.Methods The samples of 8-10 years old pupils were randomly divided into four groups of NI,IE-300,IE-500,IE-1000,in which the medium of iodine concentration in water was 19.70,367.90,655.95,and 1440.45μg/L respectively.The group of NI was control group,others were study groups.The indicators of IQ were tested by Raven's scale,and thyroid checked by ultrasonic were observed.Results The averages IQ points of the groups of NI,IE-300,IE-500,IE-1000 were 99.55,100.22,100.45 and 97.56.No statistic significance of average difference of IE groups compared with NI was found with ANOVA test in he level of α=0.05.The rates of IQ70 of groups of IE-300 to 1000 were 1.92%,2.99%,and 0,compared with the 1.86% of NI.No statistic significance of rate difference of IE groups compared with NI was found with chi-square test in the level of α=0.05.Furthermore,the total goiter rates of each group were located between 0-2.94%.Using logistic regression,education level of pupil's mothers was the main factor,which caused the mental retardation.Conclusion For the children living in the IE environment of iodine 300-1500μg/L in water,their brain dvelopment was normal,and IE couldn't be a risk factor of mental retardation.