[Repeated cross-sectional studies on urinary iodine and iodine content of salt among school-aged children from 2012 to 2014 in Yuhuan County, Zhejiang Province].

Objective: To investigate the iodine status and its change among school-aged children in their morning urine and eating salt from 2012 to 2014 in Yuhuan County, Zhejiang Province, China.

Methods: Three repeated cross-sectional studies were carried out at a same primary school in 2012, 2013 and 2014, respectively. Three classes were randomly selected from each of 3 to 5 grade by the cluster-stratified sampling every year. Totally, 1343 out of 1350 eligible children aged 8 to 10 years old were involved into this study. Their morning urine and salt eating at home were collected and tested.

Results: The overall median of urine iodine was 116.0 μg/L, and no significant change was found over year. The overall proportions of subjects with urine iodine < 50 μg/L, < 100 μg/L, and ≥ 300 μg/L were 4.8%, 38.6% and 3.5%, respectively, and there were little differences over year, gender and grade of children. An overall median of iodine from 1343 salt samples was 0.0 mg/kg and no year difference was statistically observed. The proportions of subjects consumed iodized salt significantly decreased from 25.1% in 2012 to 21.8% in 2013 and to 14.2% in 2014. There was a significant difference in urine iodine between subjects taken iodized salt or not and also a weak positive correlation between salt iodine and urine iodine.

Conclusion: The nutritional status of iodine is overall stable, proper and safety in recent 3 years among school children in Yuhuan County. The coverage rate of iodized salt is very low.