Risk factors for goiter in primary school girls in Qom city of Iran
S M Mousavi1, N Tavakoli2 and F Mardan2Received 21 October 2004; Revised 19 September 2005; Accepted 27 September 2005; Published online 23 November 2005.
Top of pageAbstractObjective: Goiter is endemic in Iran. The iodine deficiency disorders program was begun a few years ago in Iran, and the coverage of iodized salt is sufficient now. But, in a periodic yearly medical examination of primary school girls in Qom, the prevalence of goiter was above 30% in 2002. This survey was designed to study the risk factors of goiter in those students.
Design: The study was a randomized (multistage, proportional simple random sampling) case study.
Subjects and interventions: We selected and performed thyroid examinations in 1050 girl students in primary schools in Qom city of Iran in 2002. We found 284 cases: girls in primary schools had goiter in accordance with the clinical exam of World Health Organization classification. Among students who did not present with goiter in the clinical exam, we randomly selected 288 students as the control group. We used a questionnaire to evaluate them for the risk factors of goiter. ages of cases and controls were 8.71.3 and 8.91.3 years, respectively. There is no significant difference between the two groups regarding history of soya,
card for humanity, kale, turnip, fish, daily iodized salt usage, education and job of mothers, monthly family income, nationality, immigration and residential situation. By using multinomial logistic regression, we found that storage of iodized salt in open containers, odds ratio (OR): 2.201 (1.412 P value P value=0.041, district 2 of Qom city, OR: 2.880 (1.376 P value=0.005, and district 3 of Qom city, OR: 2.051(1.032 P value=0.041,
cards humanity, were the major risk factors for goiter in this population.
Conclusions: In this study, the main risk factors for goiter were storage of iodized salt in open containers, medium SES and also living in specific districts of Qom city. As the coverage of iodinized salt is over 95% in Iran, we advise the education of the family about storage of iodized salt in closed containers. We also recommend the study of the other risk factors of goiter in the different geographical areas of Iran, because of differences in the SES and nutritional habits.
Sponsorship: This study was supported by issuing permission letters for our activities: (not funding support) Qom Health Network and Medical Services, Qom Medical University, Qom Primary School Education Office, Fathemieh Medical University.
Keywords: goiter, risk factors, iodized salt storage, Iran
Top of pageIntroductionIodine is a mineral substance, which is essential for the development and growth of the human body. Iodine deficiency disorders (IDD) affect people before they are born and change children’s and adults lives. One of the most important and well known global nutritional problems is iodine deficiency, and its deficiency is the most common preventable cause of mental disability in the world (IDD Key Messages Generic Tool Kit 4). It is estimated that more than one billion people, concentrated primarily in less developed countries, are unable to consume adequate levels of iodine. Only during the last decade, it has been realized that IDDs are the leading cause of intellectual impairment (Hetzel, 1993). Goiters are the most obvious sign of IDD.
Risk factors for goiter are those that do not seem to be a direct cause of the disease, but seem to be associated in some way. Having a risk factor for goiter makes the chances of getting the condition higher, but does not always lead to goiter. The risk factors for goiter include: iodine deficiency (the most common), geographic regions with low iodine, malnutrition, goiterogen such as turnips poverty, pregnancy and a low level of education. The involvement of other factors (dietary or nondietary) besides iodine deficiency might interact in the genesis of thyroid enlargement (Zali et al., 1994).
The IDD program begun 15 years ago in Iran, using iodized salt with potassium iodated, and its coverage was sufficient (urban 95% and rural 92%) in 2000. In the periodic yearly medical examination of primary school girls in Qom city of Iran, we found that the prevalence of goiter was 30% in 2002. Why was the prevalence of simple goiter high in this population, in spite of the sufficient iodized salt coverage in this city, and after over 15 years past the IDD program? The aim of the present study was to answer this question and to examine the relations between demographic variables, habits and socioeconomic factors for goiter in these girls.
Top of pageMaterials and methodsStudy designQom city is 120 km southwest of Tehran, the capital of Iran,
playing cards against humanity, and its population is about 1 000 000. It is divided into four district areas. This case controlled study was conducted from January to May 2002, according to Qom city districts and the latest census of the number of girls in primary schools, using multistage, proportional simple random sampling. With the assumption of goiter prevalence 30%, =0.05, d=0.05 and power 80%, we selected and performed thyroid exams in 1050 girl students in primary schools. All of them were clinically examined for the presence of goiter. Examination of the thyroid gland was made by inspection and palpation according to the criteria endorsed by the World Health Organization (WHO) and the International Council for The Control of Iodine Deficiency Disorders (ICCIDD/UNICEF/WHO, 1990).
Classification of goiter is as follows:We found 284 cases of girls in primary schools who had goiter by clinical exams with WHO classification. Of students who had no goiter in clinical exam, we randomly selected 288 students as a control group. We measured age, weight, height in all cases and in the control group. Age, weight and height of each student was compared with the growth chart of weight per height and height per age, and categorized into three groups: under percentile 3, between percentile 3 and 97, and over percentile 97, for each student. Then we interviewed the mothers of these students with a simple data collection form.
Questionnaire (data collection form)We used 24 closed questions to detect the demographic variables, physical thyroid exams, goiterogen consumption, type and amount of salt usage and its type of storage, family socioeconomic situation (SES) (we classified the families into three categories socioeconomically with regard to family income, mother’s educational level, house situation, immigration and area of the city), and the nationality. We made our questionnaire standard after interviewing 30 randomly selected girls’ mothers from each group.
Statistical methodsWe used SPSS 11.5 for Windows software to manage the data and to perform descriptive and analytic statistical tests. To examine the association of each factor with the case and control groups, we used the Pearson 2 test, Fisher exact test (two sided) and Student’s t test. Univariate logistic regression analysis was performed to calculate OR with CI 95%. P value
Top of pageResultsAll students were females. ages of cases and controls were 8.71.3 years (range 7 years) and 8.91.3 years (range 6 years), P value was 0.022. There is a statistically significant difference between cases and controls with regard to age, but this statistical difference was seen due to the high sample size, and it was not clinically significant (mean age of cases and controls had 2.4 months difference), but we measured its effect by multinomial logistic regression analysis.
In Table 1, we showed the mean of weight and height of cases and controls. As the mean of weight and height in the two groups showed a statistically significant difference, we measured their effects by multinomial logistic regression analysis.
In the cases group, the frequency of grade I goiter was 236 (83.1%) and grade II was 48 (15.9%). We did not find any grade III goiter in these students.
There were no significant differences between cases and controls with regard to height/age percentile, history of kale, turnip, soya, fish, iodine and salt consumption during the 1 month before, mean daily salt usage,
crimes against humanity game, mothers’ job, mothers’ education, family poverty, family SESs, immigration and nationality. But we found a statistical significant difference between cases and controls in the frequency of weight/height percentile and also type of salt storage in the houses. These associations and their ORs has been shown in Tables 2, 3 and 4.