Iodine status of 8 to 10 years old children within 20 years following compulsory salt iodization policy in Shanghai, China

Abstract

Abstract Background In 1996, Shanghai implemented universal salt iodization and has became the last provincial unit in China to carry out this intervention. In this study, we summarized achievements in past 20 years, to provide suggestions and evidence for the next stage of iodine supplementation. Methods This study summarized and analyzed monitoring data of children from 1997, 1999, 2005, 2011, 2014, and 2017 in Shanghai. In each monitoring year, 30 streets or towns were selected using the probability-proportional-to-size sampling technique. One primary school was selected from each street or town by a simple random sampling technique. From each school, 40 children aged 8 to 10 years were randomly selected. The number of children was divided equally by sex and age. Results In 1997, 1999, 2005, 2011, 2014, and 2017, median urinary iodine (MUI) was 227.5 μg/L, 214.3 μg/L, 198.1 μg/L, 181.6 μg/L, 171.4 μg/L, and 183.0 μg/L, goiter rate was 3.07, 0.40, 0.08, 0.08, 0.86, and 1.90%, and median thyroid volume (MTvol) was 2.9 mL, 1.2 mL, 2.4 mL, 1.0 mL, 1.8 mL, and 2.8 mL, respectively. There was a linear correlation between goiter rate and median thyroid volume (MTvol) (r = 0.95, P = 0.014). Household salt iodine concentration (SIC) was dropping every monitoring (P < 0.05). There was a significant difference among different household SIC groups in MUI in 1999 and 2017, and in MTvol in 1999 (P < 0.05). No significant differences were detected in the other years. Conclusions In Shanghai, the iodine status of 8 to 10 years old children is adequate. Household SIC have little effect on iodine status of children. Future studies should analyze the dietary sources of iodine, especially from pre-packaged and prepared-away-from-home foods or meals. The regular monitoring of iodine status is important to human health.