In order to improve the iodinenutritional status of the population in Nangqian County, free iodized salt distribution, health education and other intervention measures for iodine deficiency disorders were implemented for 9 consecutive years since 2013. In May 2012 (before iodine supplementation) and September 2021 (after iodine supplementation), the same 5 townships (towns) were selected, and childrenaged 8-10 years old (half male and half female, age balanced) born locally in the central primary school of each township (town) were selected as the survey subjects. Household edible salt samples and random urine samples were collected for saltiodine and urinary iodinedetection; the second revised version of the Chinese Combined Raven's Test (rural version) was used to assess the intelligence quotient (IQ) of children. The Flynn effect (FE) gain was used to adjust IQ, the corrected IQ = (IQ starting point value - current year's IQ value) - FE gain (calculated by 0.74/year). The differences of saltiodine and urinary iodine related indexes, IQ value and corrected IQ were compared before and after iodine supplementation.
Results:
After iodine supplementation, the coverage rate of iodized salt reached 100.00% (300/300), and the consumption rate of qualified iodized salt reached95.00% (285/300), the median urinary iodine increased to 157.20 μg/L, and all indexes met the elimination standard of iodine deficiency disorders. The IQ value of childrenaged 8-10 years old after iodine supplementation was 99.00 ± 14.90, significantly higher than that before iodine supplementation (82.00 ± 13.20, F = 156.82, P < 0.001). The FE gain in 9 years was 6.66, and the actual IQ gain of childrenaged 8-10 years old after iodine supplementation was 10.34. There were statistically significant differences in IQ value before and after iodine supplementation in male and femalechildren ( F = 78.84, 78.88, P < 0.001). After iodine supplementation, there was a statistically significant difference in IQ value between children in the 8-year-old group and the 10-year-old group ( P = 0.010). There were statistically significant differences in IQ value before and after iodine supplementation in 8, 9 and 10 years old groups ( F = 55.23, 65.79, 36.85, P < 0.001).