Iodine Nutritional Status and Its Associated Factors Among Children and Adolescents in Zhejiang Province Ten Years After the Downward Adjustment of the National Salt Iodization Policy

Background: Iodine nutrition requires continued surveillance after changes in salt iodization policy. This study evaluated iodine status and associated factors among children and adolescents in Zhejiang Province, ten years after the national salt iodization standard was lowered. Methods: A cross-sectional survey employing a stratified, multistage cluster sampling design was conducted in 2022. A total of 688 participants aged 6–17 years with complete data on urinary iodine concentration, household salt iodine concentration, geographic classification, and key questionnaire variables were included in the analysis. Multivariate logistic regression analysis was performed to identify factors independently associated with iodine sufficiency. Results: Among 688 participants, the median household salt iodine concentration was 21.50 mg/kg, and iodized salt coverage was 64.68%. The median urinary iodine concentration (UIC) was 191.4 μg/L; however, 15.26% of participants had UIC < 100 μg/L. Participants in coastal areas had lower UIC levels and lower household iodized salt coverage than those in inland areas. Multivariate logistic regression analysis identified age, geographic region, and household use of iodized salt as factors significantly associated with iodine sufficiency. Conclusions: The overall iodine nutritional status among children and adolescents aged 6–17 years in Zhejiang Province is adequate. However, a certain proportion of iodine deficiency persists. Continued, targeted monitoring and health education on the appropriate use of qualified iodized salt are warranted, particularly in coastal areas and among younger children.