Study of universal salt iodization on child intellectual quotient development in Hainan province / 中国地方病学杂志

ABSTRACT

Objective To estimate the impact of universal salt iodization on child intelligence quotient (IQ) development in Hainan province. Methods In this is a cross-section study from September in 2008 to April in 2009,the observation group was historical iodine deficiency ward which includes 2 counties and 6 townships,and the control group was non-historical ward which includes 6 counties and 9 townships. Comparison of child IQ distribution according to different geographical housing position(plain,mountainous area,coast),age and sex based on the result of urine iodine examination and the IQ test of children between 8 and 10 years old. Results The median of urinary iodine of children in the observation group was 196.2μg/L which was 2.13 times of the urinary iodine median in the control group(91.9μg/L). The average IQ of children in the observation group was 94.7 which was 8.5 higher than the control group(86.2) ; IQ≤69 rate in this group was 7.7%(91/1179),and it was 8.9 percentage point lower than the control group[16.6%(253/1520)]; IQ≥ 110 rate of the group was 18.3%(216/1179),and it was 10.0 percentage point higher than the control group[8.3%(126/1520)]. The average IQ of children living in mountainous area(83.1) was the lowest in the control group. It was 3.5 and 5.1 lower than that of the children living in the plain(86.6) and coastal area(88.2) respectively; the IQ≤69 rate of children living in mountainous area [20.5%(91/443)]was the highest,and it was 3.8 and 7.1 percentage point higher than that of the children living in the plain [16.7% (89/533)]and coastal areas [13.4% (73/544)]respectively. The average IQ of children aged 8 (97.4) was similar to those aged 9(95.9) in the observation group which was 6.8 and 5.3 higher than that of the children aged 10(90.6) in the same group respectively; However,the average IQ of children aged 8,9 and 10 was close in the control group(86.8,86.3 and 85.6). The average IQ of boys(96.2) was 3.1 higher than that of the girls(93.1),and their IQ≤69 rate[6.3%(37/590)]was 2.9 percentage point lower than that of the girls[9.2% (54/589)]in the observation group. On the other hand,the average IQ(87.2) of boys was 2.1 higher than that of the girls(85.1),and IQ≤69 rate[14.5%(114/787)]was 4.5 percentage point lower than that of the girls [19.0%(139/733)]in the control group. The average IQ of children with different housing geographical position,age and sex in observation group was 5.0-12.4 higher than that of the control group; their IQ≤69 rate was 7.7-13.2 percentage point lower than that of the control group; their IQ≥110 rate was 5.6-13.0 percentage point higher than that of the control group. Conclusions Supplementing salt iodization can improve child intelligence. Supplementing iodine can increase the child IQ and reduce the child mental retardation.