Thirty-year follow-up observation of the impact of iodine fortification strategy on intellectual development of children / 中华地方病学杂志

ABSTRACT

Objective:To follow up and observe the intellectual development of school children aged 8 to 10 in Baicheng County, Xinjiang Uygur Autonomous Region, which was a severe iodine deficiency disorders region in history, before and after effective control of the disease, in order to evaluate the impact of iodine supplementation on protection of children's intellectual development and provide a theoretical basis for scientific supplements of iodine.Methods:From 1989 to 2018, Combined Raven's Test for Rural in China (CRT-RC) was used to observe the intellectual development status of 660 Uyghur school children aged 8 to 10 in Baicheng County in 1989, 2002, 2006, 2012 and 2018, respectively. Children's intelligence quotient (IQ) was calculated using CRT-RC's 1987 normal sample of rural children in the same age group; the data of average iodized salt coverage rate (C-IS) and childhood goiter rate (GR) from multiple local surveys and the median urinary iodine (MUIC) of children were collected, combined with the "Criteria for Elimination of Iodine Deficiency Disorders" (GB 16006-2008) and the United Nations International Children's Emergency Fund (UNICEF) recommended standards, the status of iodine deficiency during children's growth (IDG) was divided into complete exposure to iodine deficiency, no exposure, and semi-exposed. The Flynn effect (FE) gain was calculated using norm samples of children aged 8 to 10 in 1987, 1996 and 2006 of CRT-RC, and the differences in children's intellectual development after FE correction before and after IDG reached the standard were compared.Results:The IQ of children were (81.67 ± 14.13), (83.26 ± 14.05), (89.68 ± 13.58), (98.50 ± 14.33) and (103.23 ± 15.25) points in Baicheng County in 1989, 2002, 2006, 2012 and 2018, respectively, the difference between different years was statistically significant ( F = 58.357, P < 0.01). The three indicators of C-IS, GR, and MUIC didn't meet the standards during the IDG evaluation period in the 1989, 2002, and 2006 groups, which were the complete exposure to iodine deficiency; in the 2012 group, only the MUIC met the standard, which was semi-exposed; in the 2018 group, three indicators all met the standard, which was no exposure. The FE gains of 1987 with 1996, 1996 with 2006 were 0.96 points/year and 0.74 points/year, respectively; after FE correction, the actual gains of IQ of 2002 and 2006 compared with 1989, 2012 and 2018 compared with 2006 were - 9.57, - 6.11, 4.38, and 4.67 points, respectively. Conclusions:In iodine deficiency areas, intermittent iodine supplementation (1989 - 2009) for children exposed to iodine deficiency during growth still cannot effectively protect children's intellectual development; continuous and effective iodine supplementation (2010 - 2018) with iodized salt as the core and covering children's growth period has obvious positive effects on protection of children's normal intellectual development. In the future, we will continue to observe the influence of IDG full-cycle suitable iodine nutrition on children's intellectual development.