Different Concentration Of Iodized Salt For Preventing Iodine Deficiency Disorder

ObjectiveTo know the status in quo of preventing iodine deficiency disorders in Chongqing after universal salt iodization. And describe the characteristic of people's iodine nutrition status after taking iodized salt with different concentration; to table a proposal of iodine content that fit for people in Chongqing.Part 1 Systematic review of different concentration of iodized salt for preventing iodine deficiency disorderMethod use the principle and method of Cochrane review, we searched Cochrane library,MEDLINE,BA,PUBMED,OVID,ISI Web of Knowledge,VIP,Wangfang,CBMDisc,CNKI and hand searched 6 relevant Chinese journals, also all the reference of the paper we have already searched. We screened the studies for eligibility according to the inclusion and exclusion criteria, analyzed the included studies use Revman 4.2 software, and critically appraised the result of different concentration of iodized salt for preventing iodine deficiency disorder. Guide the project of field-test in advance according to the result.Design the iodine concentration of different group and fix on each index to evaluate.Results After screened strictly, thirteen studies were included. Via critically appraised the included studies and performed a descriptive analysis to synthesize the study outcomes, we concluded that urinary iodine level decreased as the concentration of iodized salt went down gradually. When the concentration of iodized salt went down to(35±15)mg/kg, proportion of urinary iodine median less than 100μg/L and more than 300μg/L raised and decreased respectively, and reached the recommended best level gradually.Conclusion The effectiveness of preventing iodine deficiency disorders with various concentration of iodized salt was different. Lower the concentration of iodized salt properly can not only prevent iodine deficiency disorders but also reduce the side effect of excess iodine intake to the minimum. And it can also save a lot of iodine resource. According to the result of systematic review, combined with the epidemiology standard to evaluate children's urinary iodine which raised by WHO,United Nations Children's Fund and International Council for the Control of Iodine Deficiency Disorders, we finally decided three concentration, there were 15±5mg/kg,25±5mg/kg,and 35±15mg/kg. thereinto,15±5mg/kg and 25±5mg/kg were trial groups, 35±15mg/kg was comparison group. Part 2 Iodine deficiency disorders and Iodine nutrition status of spot-area in ChongqingMethod Use method of cross-sectional study, selected Yunyang which economy was not so good and Bishan which economy was good, respectively located in the east and west of Chongqing, classified all the towns of the two countries according to its economy as good,middle and bad. Then use stratified randomization sampling method to selected three towns as field which geography condition,traffic circumstances,medical treatment condition were similar, cropper,diet custom and epidemic situation of iodine deficiency disorder and were the same, requested its feasibility is well. Selected children aged 8～10 in each three primary school, each group of children were thirty(half boy and half girl)as our object. Inspected iodine content of drinking water and soil around where people lived. We also inspected iodine content of children's urinary and their family table salt. Children's thyroid volume and intelligence quotient were inspected at the same time. Children aged ten took investigate of health education questionnaire.Results the iodine content of drinking water was less than 10 ?/L, two countries were all iodine deficiency region. Urinary iodine median of two countries were more than fitting range WHO suggested (100～200 ?/L), Yunyang is higher than Bishan (278.64 ?/L compared with 240.65 ? /L), its difference has statistical meaning (H=7.42,P<0.01), goiter rate were all more than five percent, didn't reach the standard of eliminating iodine deficiency disorders.Conclusion After universal salt iodization in Chongqing, people's iodine nutrition status had improved markedly, but children's goiter rate was still not achieve to the standard of IDD estimate, and the urinary iodine level in spot-area was a little higher if intaking iodized salt of present concentration in the long-term. The baseline situation of six towns were the same, achieve the condition of community intervention. The content of iodized salt should be adjusted if we wanted to make the urinary iodine to the best level.Part 3 Field trial of preventing iodine deficiency disorders with different concentration of iodized saltMethod Taking the field trial in the towns which were selected with 15±5mg/kg,25±5mg/kg and 35±15mg/kg concentration in salt, all the resident were as the object. Use simple randomization method to decide town who will be in which groups.Results After ten months intervention, the result showed iodized salt coverage rate was passable. Urinary iodine median of group 15±5mg/kg compared with comparison group, its difference had statistical meaning (Bihan: H=10.5496,P=0.0012;Yunyang:H=11.8960,P=0.0006). Urinary iodine was increased along with the addition of iodine in salt. We did a linear correlation showed urinary iodine had a good relativity with iodine in salt(r=0.18207,P<0.0001). There were no differences between the proportion of children's urinary iodine less than 100 ?/L before and after intervention with 15±5mg/kg iodine content. The result of thyroid inspection showed there were no differences of goiter rate between different towns after taking iodized with different content when using palpate or B ultrasonic, even each town compared with itself before and after intervention. Clue to the phenomena that using three groups of different iodine content we designed to preventing iodine deficiency disorders, its effect was consistent.Conclusion After ten months intervention with three different iodine content, urinary iodine of people using 15±5mg/kg ionized salt was more reasonable. Band goiter rate together, we judged the suitable iodine concentration in salt for local people in Chongqing may low down properly.