Analysis of intelligence quotient of school children surveyed in Dalian city of Liaoning province during 2006 to 2009

Abstract

Objective To obtain scientific data for control of iodine deficiency disorders(IDD) by reviewing the surveillance information of school children intelligence quotient(IQ) after the implementation of universal salt iodization. Methods One thousand five hundred and eighty children were selected from 11 primary school in Dalian city of Liaoning province during 2006 to 2009. IQ was measured by Combined Raven Test-C2(CRT-C2) in China. Groups of IQ were classified as outstanding(≥ 130), excellent (120- 129), above average (110- 119), average (90 - 109), below average(80 - 89), margin(70 - 79), low(≤69). Urinary samples of children were collected randomly. Urinary iodine were determined by As-Ce catalytic spectrophotometry. The growth characteristics of IQ were analyzed according to surveillance year and born year. Results The average IQ of children aged 8-10 were 110.4 ± 14.0,112.5 ± 12.4,117.2 ± 11.4,116.2 ± 12.6, respectively, increased year by year from 2006 to 2009. Its average annual increase from 2007 to 2009 were 2.1,3.4,1,9 compared with the IQ in 2006 respectively. The medians of urinary iodine were 224.7,266.7,222.1 μg/L from the year 2007 to 2009, respectively, which were all between 200 - 300 μg/L and can be classified as more than adequate level. The average IQ of children born during the year of 1994 to 2000 were 106.7 ± 13.0,108.1 ± 13.9,108.5 ± 13.4,111.3 ± 14.3,113.6 ± 12.5,115.3 ± 12.3,119.8 ± 11.2, respectively. Its average annual increase from 1995 - 2000 were 1.4,0.9,1.5,1.7,1.7,2.2 compared with the IQ born in 1994 respectively. The ratio of IQ in margin group and low group were all below 2% ; the ratio was increasing in excellent group and outstanding group and decreasing in average group and below average group significantly year after year(x2 = 52.471,34.329,66.483,11.148, all P<0.01). Conclusions Universal salt iodization improves IQ scores. IQ index should be brought into the surveillance project and put in use in IDD control. Key words: Iodine; Deficiency diseases; Salts; Intelligence