Statistical analysis of factors affecting the result of using iodized salt in controlling of iodine deficiency disorders in Zhangjiakou from 2000 to 2008 / 中国地方病学杂志

ABSTRACT

Objective To find out the relation between element (non-iodized salt and iodized salt that below standard) and epidemic strength of iodine deficiency disorders and level of iodine, in order to find out the factors affecting the result of using iodized salt in controlling of this disorders. Methods Retrospective analyses was used in the study. Six counties were selected randomly from Zhangjiakou every year from 2000 to 2008, and these counties were randomly divided into non-iodized salt group (the ratio of non-iodized salt > 5%), iodized salt below standard group (the ratio of qualified iodized salt < 95%) and control group (the ratio of using qualified iodized salt > 95%). The indexes from different groups were compared as well as the ratio of large thyroid syndrome in children aged 8-10 years and the level of iodine in urine. Results The number of iodized salt monitored were 12 468 units from 2000 to 2008. We examined 5655 children's thyroid and collected 4404 urine samples. The median was 30.1 mg/kg for the average of iodized salt and 7.30% (232/3180) for ratio of non-iodized salt in noniodized salt group, while 30.9 mg/kg and 93.10%(3776/4056) in iodized salt below standard group, and 32.0 mg/kg and 99.27%(5194/5232) in control group. Compared the median of the three groups[5.31%(78/1468) ,4.84% (92/1902) ,2.06% (47/2285)], we observed significant difference (χ2 = 72.07, P < 0.05), especially the ratio of large thyroid in non-iodized salt group which was apparently higher than that of the control group (χ2 = 8.70, P < 0.017). However there was no significant difference between iodized salt below standard group and non-iodized salt group(χ2 = 6.83, P > 0.017) and control group(χ2 = 5.65, P > 0.017). The median of urinary iodine was 188.20 μg/L in non-iodized salt group, 219.62 μg/L in iodized salt below standard group and 262.39 μg/L in control group, indicated that the index in control group was higher than that of others. Conclusion Both of non-iodized salt and iodized salt below standard have effect on prevalence of child iodine deficiency disorders, especially the non-iodized salt.