The Characteristics of Iodine Nutrition Status in China after 20 Years of USI: An Epidemiology Study Covering 31 Provinces

Abstract

Background: The mandatory universal salt iodization (USI) program has been implemented in China for about twenty years to correct iodine deficiency. At present, the actual iodine nutrition status of Chinese residents and whether they are adversely affected by iodine excess are issues of general concerns. \n \nMethod: A nationally representative cross-sectional study was conducted. 78,470 participants, aged 18 or older, were enrolled from all 31 provincial regions of mainland China. The participants were interviewed and given a questionnaire. Urine iodine concentration (UIC) were measured by ICP-MS (inductively coupled plasma mass spectrometry) method. The goiter was examined by thyroid ultrasonography. The iodine category was based on the criteria of WHO. \n \nResults: The iodized salt coverage is 95·37% in the general population. The median urine iodine (MUI) was 177·89μg/L (interquartile range, 117·89-263·90μg/L) in the general population with goiter prevalence 1·17% (95%CI, 0·95-1·43%). The MUI was 199·7(interquartile range, 128·46-303·02) in school age children with prevalence of goiter 3·50% (95% CI, 2·93% to 4·13%). The percentage of moderate iodine deficiency (UIC<50μg/L) was 3·43%. The subjects with adequate iodine and more than adequate iodine in total accounting for 63·44% of the whole population. The data also manifested that gender, age, ethnic, geographic factors, BMI, smoking habits, education and income levels have a certain degree of influence on the iodine nutrition level. \n \nConclusion: The mandatory USI program in China has successfully eliminated iodine deficiency disorders for 20 years. Our epidemiological investigation suggested that the iodine nutrition level of Chinese residents is generally within the safe range. \n \nFunding Statement: This work is supported by the Research Fund for Public Welfare from National Health and Family Planning Commission of China (Grant No. 201402005). \n \nDeclaration of Interests: There is no conflict in interest. \n \nEthics Approval Statement: The research protocols were approved by the Medical Ethics Committee of China Medical University.