Iodine nutritional status before and after the adjustment of edible salt iodine level in Xi'an City

Objective To understand the current situation of iodine deficiency disorders (IDD), iodine nutritional status and implementation situation of the prevention and control measures before and after the adjustment of edible salt iodine level in Xi'an City, and to provide a basis for scientific prevention and control of IDD. Methods In 2011, seven counties (areas) of Xi'an City were selected, including Lintong, Weiyang, Chang'an, Lantian, Gaoling, Zhouzhi and Huxian, and five subareas were selected according to the five directions as east, west, south, north and centre in each county(area), one township was selected in the centre subarea and two townships were selected in other subareas, four villages were selected in every township, edible salt samples of eight households were selected in every village to detect salt iodine. Six areas of Xi'an City were selected, including Yanta, Beilin, Yanliang, Lianhu, Xincheng and Baqiao, one township was selected according to the five directions as east, west, south, north and centre in each county, four villages were selected in every township, edible salt samples of 15 households were selected in every village to detect salt iodine. One school was respectively selected according to the five directions as east, west, south, north and centre in 13 counties, 42 children aged 8-10 were selected in every school to detect goiter. Two schools were selected in Beilin, Lianhu and Xincheng, respectively, 30 children aged 8-10 were selected in every school to detect urine iodine. The remaining 10 counties were respectively divided according to the five directions as east, west, south, north and centre, two schools were selected in the centre subarea, 30 children aged 8-10 were selected in every school to test urine iodine, one school was selected in other subareas, 15 children aged 8-10 were selected in every school to detect urine iodine. In 2015, 13 counties were selected, one township was selected according to the five directions as east, west, south, north and centre in each county, four villages were selected in every township, and edible salt samples of 15 households were selected in every village to detect salt iodine. One school was selected in every township, 42 children aged 8-10 were selected in every school to detect goiter. Meanwhile, 40 children aged 8-10 were selected in every school to detect urine iodine. Results The median of salt iodine was 33.70 mg/kg in 2011, which was higher than that in 2015 (24.96 mg/kg), the difference was statistically significant (Z = 31.059, P﹤ 0.05). In 2012 and 2015, the coverage rates of iodized salt were 99.79% (3 808/3 816) and 99.90% (3 896/3 900), consumption rates of qualified iodized salt were 99.32% (3 791/3 816) and 97.64% (3 808/3 900). The rate of weighted goiter in 2011 was 2.76%, which was higher than that in 2015 (1.17%), the difference was statistically significant (χ2 = 15.11, P﹤0.01). The median of urinary iodine was 292.5 μg/L in 2011, which was higher than that in 2015 (259.0 μg/L), the difference was statistically significant (Z = 2.862, P ﹤ 0.05). Conclusion The population iodine nutritional status is more than sufficient in Xi'an City after adjustment of edible salt iodine level, there is still a space for lowering the iodine level in edible salt. Key words: Iodine; Salt; Goiter; Urine; Analysis