Objectives To investigate the effect of water-borne excessive iodine on the intelligence of children in China.
Methods Literatures on the relationship between water-borne excessive iodine and the IQ of children were searched by computer from the database and manual retrieval.A total of 9 relevant literatures that met the inclusion criteria were included for Meta-analysis.Meta-analysis was performed with RevMan 5.2.
Results In the 9 literatures involved with 13 researches, 1 392 children were included as a excessive iodine group and 1 175 children as a control group, the IQ in the excessive iodine group decreased 0.17 points (95% CI-0.33, -0.01) significantly lower than that in the control group(Z=2.10, P < 0.05).When literatures were distinguished by water iodine concentration (WI), in the lower water iodine area (WI < 800 μg/L), no significant difference (Z=1.07, P > 0.05) was observed on the IQ of children between the excessive water iodine group and the control group; and in the higher water iodine area (WI > 800 μg/L), the IQ of children in the excessive iodine group decreased 0.23 (95% CI~-0.44, -0.02) points significantly lower than the control group (Z=2.17, P < 0.05).When the data were analyzed by different IQ test methods, the IQ of children tested by CRT in the excessive iodine group decreased 0.9 points (95% CI-2.80, 0.85) lower than the control group, but there was no significant difference between the two groups (Z=1.05, P > 0.05).When the IQ of children was tested by Chinese Binet Intelligence Scale, the excessive iodine group decreased 6.67 points (95% CI-9.62, -3.71) and significantly lower than the control group (Z=4.42, P < 0.05).When the IQ of children was tested by Wechsler Intelligence Scale, the IQ of children decreased 7.23 points (95% CI-10.32, -4.14) and significantly lower than the control group (Z=4.58, P < 0.05).
Conclusions There was no sufficient evidence to prove that excessive water iodine could cause a decrease of IQ in children.
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