Effect of reducing iodine excess on children's goiter prevalence in areas with high iodine in drinking water.

The purpose of the study was to evaluate the effect of removing iodized salt on children's goiter prevalence in high iodine area (HIA). A total of 452 and 459 children aged 8-10 years old were selected by simple random sampling method before and after removing iodized salt from their diet in three towns with median water iodine content of 150-300 µg/l in Hengshui city of Hebei province of China. Their goiter status was judged using the thyroid volume (Tvol) reference for body surface area recommended by the WHO. After removing iodized salt, children's overall median urinary iodine content (MUIC) decreased from 518 (IQR 347,735) µg/l to 416 µg/l (IQR 274,609). Children's MUIC across sex and age group decreased significantly. The overall goiter prevalence in the three towns significantly decreased from 32.96 % (149/452) to 6.54 % (30/459) (P < 0.001). The goiter prevalence in 8-, 9-, and 10-year-old children decreased, respectively, from 38.04 % (35/92), 30.57 % (59/193), and 32.93 % (55/167) to 6.10 % (10/164), 6.75 % (11/163), and 6.82 % (9/132). The goiter prevalence in boys and girls decreased from 34.01 % (83/244) and 31.73 % (66/208) to 6.19 % (14/225) and 6.87 % (16/234), respectively. The decreases in children's goiter prevalence across gender and age groups were all statistically significant. The present study revealed that children's goiter prevalence decreased significantly after removing iodized salt from their diet for about one and half years in the HIA in Hebei province.

Iodised salt contribution to iodine nutrition status of pregnant and lactating women.

Sufficient iodine intake by pregnant and lactating women is crucial to their offspring's cognitive development. The aim of the present study was to explore the impact of iodised salt intake on the iodine status of pregnant and lactating women. Thirty towns were selected from 211 towns in the rural areas of Shijiazhuang city using probability proportionate to size sampling in this cross-sectional survey. In each selected town, forty pregnant women and forty lactating women were randomly selected to contribute urine samples to determine iodine content. The median urinary iodine content (UIC) of 1200 pregnant women in all was 146 (interquartile range (IQR) 88-239) µg/l. The median UIC in the first, second and third trimesters were 166 (IQR 92-276) µg/l, 145 (IQR 83-248) µg/l and 134 (IQR 79-221) µg/l, respectively. The median UIC in the first trimester was significantly higher than that in the third trimester (P= 0.04). The median UIC of 1200 lactating women in all was 120 (IQR 66-195) µg/l. Their median UIC in every 4-week block was higher than the WHO criteria except in weeks 25-28 and weeks 33-36 of lactation. Pregnant women's median UIC did not correlate with median salt iodine (MSI) (P= 0.402); however, there was a linear correlation between MSI and the lactating women's median UIC (P= 0.007). Iodised salt failed to provide adequate iodine to pregnant women possibly due to limited intake of iodised salt during pregnancy, though it was found to provide adequate iodine to lactating women in the rural areas of Shijiazhuang city.

Impact of removing iodised salt on children's goitre status in areas with excessive iodine in drinking-water.

The impact of removing iodised salt on children's goitre status in a high-iodine area (HIA) remains unclear. The aim of the present study was to explore the changes in the prevalence of goitre in children after removing iodised salt from their diet. For this purpose, three towns with the median water iodine content of 150-300 µg/l were selected randomly in Hengshui City, Hebei Province, China. A total of 452 and 459 children were randomly selected from the three towns in order to measure thyroid volume by ultrasound before and after removing iodised salt, respectively. Their goitre status was judged using the criteria of age-specific thyroid volume recommended by the WHO. After removing iodised salt, the overall median urinary iodine content (MUIC) of children decreased from 518 (interquartile range (IQR) 347-735) to 416 (IQR 274-609) µg/l. The MUIC of children across sex and age group decreased significantly except for the age group of 9 years. The overall prevalence of goitre in the three towns significantly decreased from 24·56% (n 111/452) to 5·88% (n 27/459) (P< 0·001). Goitre prevalence in children aged 8-10 years decreased from 33·70% (n 31/92), 23·32% (n 45/193) and 20·96% (n 35/167) to 6·10% (n 10/164), 5·52% (n 9/163) and 6·06% (n 8/132), respectively. Goitre prevalence in boys and girls decreased from 27·05% (n 66/244) and 21·63% (n 45/208) to 6·66% (n 15/226) and 5·15% (n 12/233), respectively. The decreases in the prevalence of goitre in children across sex and age group were all statistically significant. The present study revealed that goitre prevalence in children decreased significantly after removing iodised salt from their diet for about 1·5 years in the HIA in Hebei Province.

Impact of removing iodized salt on the iodine nutrition of children living in areas with variable iodine content in drinking water.

PURPOSE: Excess iodine in drinking water has emerged as a public health issue in China. This study assesses the effectiveness of removing iodized salt on reducing the iodine excess in populations living in high-iodine areas and also to identify the threshold value for safe levels of iodine in water. METHODS: Twelve villages from 5 cities of Hebei Province with iodine content in drinking water ranging from 39 to 313 µg/l were selected to compare the urinary iodine content of children aged 8-10 years before and after removing iodized salt from their diet. RESULTS: For 3 villages where median water iodine content (MWIC) was below 110 µg/l, following the removal of iodized salt (the intervention), the median urinary iodine content (MUIC) reduced to under 300 µg/l decreasing from 365, 380, 351 to 247, 240, 281 µg/l, respectively. However, the MUIC in the 9 villages with MWIC above 110 µg/l remained higher than 300 µg/l. The children's MUIC correlated positively with the MWIC in the 12 villages (p ≤ 0.001). The linear regression equation after removing iodized salt was MUIC = 0.6761MWIC + 225.67, indicating that to keep the MUIC below 300 µg/l (the iodine excess threshold recommended by the WHO) requires the MWIC to be under 110 µg/l. CONCLUSION: Removing iodized salt could only correct the iodine excess in the population living in the areas with MWIC below 110 µg/l. In the areas with water iodine above 110 µg/l, interventions should be focused on seeking water with lower iodine content. This study suggests a threshold value of 110 µg/l of iodine in drinking water to maintain a safe level of dietary iodine.

Goitre prevalence and epidemiological features in children living in areas with mildly excessive iodine in drinking-water.

The prevalence of goitre in areas with mildly excessive iodine in drinking-water is still under debate. The aim of the present study was to explore the prevalence of goitre and its epidemiological characteristics in these areas using WHO criteria. To this end, three towns with a median water iodine (MWI) of 150-300 µg/l were selected randomly in Hengshui City of Hebei Province of China, and one town with a MWI of 105 µg/l was chosen as a control. A total of 452 children in the three towns and 120 children in the control town were randomly selected to measure thyroid volume (T vol) by ultrasound. The goitre status of these children was judged using the criteria recommended by the WHO. The overall goitre prevalences in the three towns were 24·6 % (111/452) by age-specific T vol and 33·0 % (149/452) by body surface area (BSA)-adjusted T vol, which were significantly higher than that in the control town by both age-specific T vol (14·0 % (17/120), P= 0·015) and BSA-adjusted T vol (17·5 % (21/120), P= 0·001). Significant differences were found neither in goitre prevalences across sex by both age-specific T vol (P= 0·078) and BSA-adjusted T vol (P= 0·692) nor in that across age group by both BSA-adjusted T vol (P= 0·461) and age-specific T vol (P= 0·183). The present study found a high prevalence of goitre in children living in areas with mildly excessive iodine in drinking-water in Hebei Province. No significant differences were found in goitre prevalences across sex and age group. These results suggest that the T vol reference values recommended by the WHO could be too low for Chinese children.

An epidemiological survey of children's iodine nutrition and goitre status in regions with mildly excessive iodine in drinking water in Hebei Province, China.

OBJECTIVE: To identify children's iodine nutrition and goitre status in areas with mildly excessive iodine in drinking water. DESIGN: A cross-sectional survey. Probability proportional to size sampling was employed to randomly select children from thirty townships where the median iodine content in drinking water ranged from 150 to 300 µg/l; their urinary iodine concentrations were determined and their thyroid volumes were measured by ultrasound. Drinking water samples and salt samples from the villages where the children lived were collected using a systematic sampling method. SETTING: Hebei Province of China. SUBJECTS: A total of 1259 children aged 8-10 years (621 boys and 638 girls). RESULTS: Children's median urinary iodine concentration was found to be 418·8 µg/l, and the iodine concentration was >300 µg/l for 68·3 % (248/363) of the urine samples. Children's median urinary iodine concentration in villages with median salt iodine >10 mg/kg was significantly higher than that in villages with median salt iodine <5 mg/kg (442·9 µg/l v. 305·4 µg/l, P ≈ 0). The goitre rate of 1259 children examined by ultrasound was 10·96 %. CONCLUSIONS: The iodine intake of children living in areas with mildly excessive iodine in drinking water in Hebei Province was found to be excessive. The measured iodine excess in the sampled children is exacerbated by consumption of iodized salt. Goitre was identified in these areas; however, due to the limitation of the current criteria for children's thyroid volume, a comprehensive assessment of the prevalence of goitre in these regions could not be made and further study is required.

Control of iodine deficiency disorders following 10-year universal salt iodization in Hebei Province of China.

OBJECTIVE: To evaluate the effectiveness of universal salt iodization (USI) for the control of IDD in Hebei province since it was implemented in 1995, identify the problems currently encountered in the implementation of USI and provide practical proposals for addressing these problems. METHODS: Probability proportionate to size sampling (PPS) was employed in the surveillance of IDD, for which a total of 1200 school children aged 8-10 years were randomly selected from 30 counties around the whole province during each IDD survey. The iodine content of salt was determined quantitatively with the titration method. The iodine content of urinary samples was measured by the method of ammonium persulfate oxidation. RESULTS: The coverage of iodized salt increased from 65.0% in 1995 to 98.0% in 1999, then decreased to 88.1% in 2005 which was below the national standard of 90%. The median urinary iodine of children aged 8-10 years varied between 160.1 microg/L and 307.4 microg/L, which was above the national standard. The proportion of urinary samples with iodine content above 300 microg/L was over 30% in 2005, implying exorbitant iodine nutrition among the children. The goiter rate (TGR) among children aged 8-10 years dropped from 11.8% in 1995 to 2.7% in 2005, indicating that the spread of endemic goiter was under control. CONCLUSION: Preliminary elimination of IDD was achieved by USI in Hebei province. Nevertheless, some problems still existed in USI such as non-iodized salt competition, over iodization and un-standardized iodization. In order to address these problems, the management and supervision of salt market needs to be strengthened to prevent non-iodized salt from reaching households; updating equipment and modifying techniques are also necessary to ensure the quality of iodized salt; to clarify the causes of excessive urinary iodine content, the various sources of iodine from the diet need to be investigated in the future.