Objective: Through a two-year follow up program, this study was to analyze the urinary iodine frequency of a cohort in the intervention trial, concerning different doses of salt ionization, so as to explore the selection of appropriate concentration of salt ionization.
Methods: A multistage cluster sampling method was used to select three townships in two countries for community intervention with different doses [(15±5) mg/kg, (25±5) mg/kg, (35±5) mg/kg] of salt ionization.
Results: After intervention, the median of urinary iodine was reduced among the population. The urinary iodine frequencies of (15±5) mg/kg and (25±5) mg/kg among groups of children were mainly concentrated in 100-200 µg/L and 200-300 µg/L paragraphs in A county. While the 300 µg/L paragraph had an overall decline in B county, the 100 µg/L and 200 µg/L paragraph ratio increased but the trend seemed to be slow. The 100-300 µg/L paragraph of the four treatment groups took a larger proportion and kept smooth in a more ideal state. However, the control group still maintained at above 250 µg/L level.
Conclusion: The iodine supplementation should be gradually implemented in Chongqing. The doses of salt ionization should be reduced from the current (35±15) mg/kg to (25±5) mg/kg in the economically developed areas. At the same time, we need to continuously follow the changes of the condition.