Thyroid Research and Practice

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 16  |  Issue : 2  |  Page : 71--75

Iodine nutrition status in schoolchildren of Dhaka city in Bangladesh


Mohammad Atiqur-Rahman, Md Fariduddin, Mashfiqul–Hasan, Nusrat–Sultana, Sharmin–Jahan, Bajarang Kumar Rauniyar, Md Rafiq-Uddin, Jobaida–Naznin, Yasmin–Aktar, Muhammad Abul Hasanat 
 Department of Endocrinology, Bangabandhu Sheikh Mujib Medical University, Shahbagh, Dhaka, Bangladesh

Correspondence Address:
Muhammad Abul Hasanat
Department of Endocrinology, Block D, Room No. 1524, Bangabandhu Sheikh Mujib Medical University, Shahbag, Dhaka
Bangladesh

Abstract

Objectives: The objective of this study was to observe iodine nutrition status (urinary iodine [UI] and total goiter rate [TGR]) of schoolgoing children with the age of 6–12 years in Dhaka city. Materials and Methods: This study comprised 530 schoolchildren of 6–12 years of Dhaka city of Bangladesh selected by multistage random sampling. Goiter classified according to the WHO/ICCIDD/UNICEF, and UI was assessed. UI was estimated using wet digestion method. Results: Iodine nutrition status revealed 83.2% children as deficient, which was relatively more in 6–8 years group (89.5%), followed by 9–10 years (80.6%) and 11–12 years (77.2%), (P = 0.008). Out of 530 children, 55.7% had no goiter (295/530), whereas 20.2% (107/530) had Grade I and 24.2% (128/530) had Grade II goiter. There was no statistical difference for iodine sufficiency/deficiency between the children with or without goiter (χ2 = 0.129, P = 0.719). Highest mean (± standard error of mean [SEM]) and median UI was found in low socioeconomic class (81.48 ± 7.84 and 78.85 μg/L, respectively), followed by average (75.12 ± 6.31 and 65.11 μg/L, respectively) and high socioeconomic status (47.81 ± 2.68 and 34.82 μg/L, respectively) (P < 0.001). UI values were comparably higher in children whose parents were aware of iodized salt intake than those who were not (aware vs. unaware: mean [±SEM], 71.52 ± 8.90 vs. 57.20 ± 2.79, P= 0.116; median 51.43 vs. 38.72). Conclusions: Iodine nutrition status of children in Dhaka city of Bangladesh was found to be insufficient as yet. TGR is still much higher though not solely related to iodine nutrition status. Continuous surveillance over the matter is very much needed for a satisfactory iodine nutrition status.



How to cite this article:
Atiqur-Rahman M, Fariduddin M, Mashfiqul–Hasan, Nusrat–Sultana, Sharmin–Jahan, Rauniyar BK, Rafiq-Uddin M, Jobaida–Naznin, Yasmin–Aktar, Hasanat MA. Iodine nutrition status in schoolchildren of Dhaka city in Bangladesh.Thyroid Res Pract 2019;16:71-75


How to cite this URL:
Atiqur-Rahman M, Fariduddin M, Mashfiqul–Hasan, Nusrat–Sultana, Sharmin–Jahan, Rauniyar BK, Rafiq-Uddin M, Jobaida–Naznin, Yasmin–Aktar, Hasanat MA. Iodine nutrition status in schoolchildren of Dhaka city in Bangladesh. Thyroid Res Pract [serial online] 2019 [cited 2020 Sep 22 ];16:71-75
Available from: http://www.thetrp.net/text.asp?2019/16/2/71/262733


Full Text



 Introduction



Iodine deficiency disorder (IDD) is one of the major global public health problems. Over one-half of the children having low iodine intake falls into the following two regions: 76 million in Southeast Asia and 58 million children in Africa.[1],[2] Bangladesh, a country of Southeast Asia, is one of the most affected one by IDD. Goiter is the most visible manifestation of IDD.[3] Iodine nutrition status in any population is generally determined by urinary iodine (UI) concentration, the goiter rate, serum thyroid stimulating hormone and serum thyroglobulin. These indicators are regarded as complementary. In practice, UI is most often used to determine iodine nutrition.[3] In 1993, an extensive IDD survey in Bangladesh revealed low UI concentration (<100 μg/L) in 69%, a goiter rate of 47.1%, and prevalence of cretinism 0.5% population, where children were more affected.[4] Following the release of the survey findings, the Salt Bye-Law was passed in 1994, and by 1995, all registered salt factories in the country were equipped with salt iodization plant with UNICEF assistance, and iodized salt became available throughout the country. Between 1993 and 1999, the total goiter rate (TGR) among the population fell from 47.1% to 17.8%, and biochemical iodine deficiency fell from 68.9% to 43.1%.[5],[6] In 2004–2005, National Survey on IDD and universal salt iodization (USI) revealed a remarkable change in iodine nutrition status. TGR decreased from 49.9% in 1993, 17.2% in 1999, and 6.2% in 2004–2005. Iodine deficiency in children decreased from 69% in 1993 to 42.5% in 1999 and to 33.8% in 2004–2005. Median UI increased from 54 μg/L in 1993 to 126 μg/L in 1999 to 163 μg/L in 2004–2005.[5] However, National Micronutrients Survey 2011–2012 conducted in collaboration of Institute of Cholera and Diarrheal Disease Research, Bangladesh UNICEF, Bangladesh, Global Alliance for Improved Nutrition, and the Institute of Public Health and Nutrition again observed acceleration of iodine deficiency toward 40.0% in 2012.[7] Therefore, continuous surveillance of iodine nutrition status is needed to prevent IDD. This study was designed to determine iodine nutrition status by estimating UI concentration along with the presence of goiter in schoolgoing children of 6–12 years in Dhaka city.

 Materials and Methods



Study design

It comprised 530 children recruited on the basis of multistage random sampling [Figure 1]. Dhaka city is divided into north or south city corporation each having five zones. One school from each zone was selected by simple random method. Fifty students from each school (10 students from each class: Class I to Class V) were selected by systemic random sampling. Data were collected using a semistructured questionnaire. This study was conducted during January 2014–September 2015.{Figure 1}

With prior informed consent, study individuals underwent clinical examination for goiter along with required anthropometry, and relevant history was recorded in a structured questionnaire. Five ml spot urine sample was collected in screw-capped deiodinized plastic cups and transported in a cold box to be preserved within 6 h in tightly sealed deiodinized Eppendorf in duplicate under −20°C until final analysis of UI. Meticulous attention was given to avoid contamination with iodine at all stages. One Eppendorf from each sample was kept in reserve for replicate testing (if necessary). The iodine nutrition status in schoolchildren and classification of goiter were determined according to the recommended WHO/UNICEF/ICCIDD criteria.[3]

Ethical aspects

The study was done after prior approval by the Institutional Review Board. All parents/legal guardians of the students included in this study were informed about the nature of the study and agreed to participate voluntarily in this study. Informed written consent from parents/legal guardians was obtained through the school authority.

Analytic methods

UI was estimated using the wet digestion method of Dunn et al. with modification of Sandell and Kolthoff involving colorimetric estimation of the rate of discoloration of ceric ammonium sulfate as an inverse measure of organic iodine present. Iodine status (as deficient of sufficient) was considered on the basis of UI cutoff at 100 μg/l, as recommended by WHO as well as ICCIDD.[3],[8],[9]

Statistical analysis

Data were analyzed using IBM SPSS Statistics for Windows version 22.0 (IBM Corp, Armonk, NY, USA) and presented as mean (±standard deviation [SD]/standard error) or median (with interquartile range [IQR]) and frequencies as applicable. Comparison among the age groups of children for parametric values (UI and age) was done by one-way ANOVA. Frequency of iodine deficiency among the individuals was compared by Chi-square test. Iodine status was dichotomized as adequate and deficient using the above-mentioned cutoff value to see the independent influence of other factors, namely age, socioeconomic status, and awareness of iodine on human health by multiple regressions analysis. Pearson's or Spearman correlation test was used to see the relationship among the iodine level with age, socioeconomic status, and presence of goiter. P ≤ 0.05 was considered as statistically significant.

 Results



Mean age (±SD) of the participants was 9.18 ± 1.51 years. Of them, 275 (51.9%) were boys and 255 (48.1%) were girls. In the socioeconomic context, 59.3% were of good status, 31.9% average, and 8.8% of poor economic status. About 60% of children had normal body mass index (BMI), whereas 20.6% were underweight, 10.9% overweight, and 9.2% were obese. Out of 530 children, 55.7% had no goiter (295/530), the rest 20.2% (107/530) had Grade I, and 24.2% (128/530) had Grade II goiter [Table 1].{Table 1}

Only 16.79% of participating children had sufficient iodine nutrition status on the basis of UI excretion. Among 83.21%, who had deficient iodine nutrition, 42.64% were moderately deficient, 22.26% mildly deficient, and 18.30% severely deficient [Figure 2].{Figure 2}

The highest mean (±standard error of mean) and median UI were observed in the age group of 11–12 years (72.52 ± 5.05 μg/L and 63.85 μg/L, respectively), followed by 9–10 years (60.01 ± 3.85 μg/L and 40.12 μg/L, respectively) and 6–8 years (49.20 ± 4.83 μg/L and 33.38 μg/L, respectively), which was statistically different (P = 0.005). However, overall iodine deficient status was 83.2%, which was relatively more in the 6–8 years group (89.5%), followed by the age group of 9–10 years (80.6%) and 11–12 years (77.2%), which was significantly different (P = 0.008) [Table 2]. Unlike the age groups, there was no significant difference for the mean value of UI (boys vs. girls 57.67 ± 2.85 μg/L vs. 59.65 ± 4.60 μg/L, P = 0.710) between the two gender groups, and median values were nearly equal (40.74 μg/L and 38.88 μg/L, respectively). Frequency of iodine deficient status was more than 80% in both boys (80.4%) and girls (86.3%) as shown in [Table 3]. As shown in [Table 4], median (IQR) UI was relatively better in low socioeconomic status (78.85 [44.32–110.00] μg/L), followed by average (65.11 [29.72–102.68] μg/L) and high (34.82 [21.50–53.39] μg/L) UI. [Figure 3] depicts the frequency of goiter in relation with deficient or sufficient UI status. UI excretion was significantly and positively correlated with age of children (r = 0.145, P = 0.001) and awareness about iodine on health (r = 0.091, P = 0.036), whereas BMI (r = −0.173, P < 0.001) and socioeconomic condition (r = −0.300, P < 0.001) were significantly and negatively correlated with UI. There was no correlation between goiter and UI excretion [Table 5].{Table 2}{Table 3}{Table 4}{Figure 3}{Table 5}

Multiple regression analysis revealed that age (P = 0.001), socioeconomic condition (P = 0.009), and BMI (P = 0.001) were independent predictors of UI excretion [Table 6].{Table 6}

 Discussion



USI has been introduced in almost each and every country of the world, including Bangladesh encompassing people of all ages and socioeconomic strata. The present study was designed to assess the iodine nutrition status in terms of UI and goiter in schoolgoing children of 6–12 years, a vulnerable group of population for IDD, in Dhaka city of Bangladesh.

In this study, it was found that both median and mean UI concentration of schoolchildren are moderately deficient and vary among the age groups. Higher was the age, better was the UI concentration. There was no difference in iodine status either between boys and girls or between the schoolchildren with or without goiter. However, iodine status varied significantly among socioeconomic strata, higher UI in low socioeconomic group whereas lowest in the high socioeconomic group. The group who were relatively aware of importance of iodized salt had better UI concentration. UI concentration also showed inverse relationship with BMI. Goiter rate was found to be 44.3%, which is higher than that in previous studies.[5] It was interesting to observe that more than 80% of children despite taking iodized salts were found to have a UI level lower than the cutoff 100 μg/L as recommended by the WHO/ICCIDD/UNICEF.

The observed lower UI in high socioeconomic group than that of low socioeconomic group may be attributable to the fact that children of high socioeconomic group are fond of fast foods which contains less iodine. However, iodine insufficiency was not different among children with or without goiter. Furthermore, the presence of goiter gradually increased with the increment of age. Therefore, it seems pertinent to assume that goiter is also influenced by other factors than merely iodine insufficiency as, for example, part of pubertal changes in children and goitrogens.[10],[11]

Implementation of USI has improved iodine nutrition status, which was observed in the survey of 1993, 1999, and 2004–2005. However, the present observation does not fit with the trend indicating some loopholes in this matter. The paradox behind the decline in iodine nutrition status is really illusive, as all the children were taking iodized salt. Hence, the issue becomes highly debatable in context to the appropriateness of iodization, all through the procedure from packaging, marketing, and consumption.

Children of younger age group exhibited significantly lower level of UI in the present study, which might have been caused by their dependence on milk and milk-based formulas lacking sufficient iodine. Reduced iodine intake may cause reemergence of IDD as described by Li et al. in 2001.[12] In 1990, the median UI excretion of Australian schoolchildren was around 200 μg/L, which decreased to <100 μg/L a decade later. The major postulated reasons for this decrement were the reduction of iodine in milk since the dairy industry replaced iodine-rich cleaning solutions with other sanitizers and <10% of the local population were using iodized salt during the study period. In another study, Ara et al.[13] found that though median UI concentration of adolescent girl was 125 μg/l at national level, it was considerably low in Dhaka division (95 μg/l). They justified the observation as part of washout effect of soil Iodine resulting from heavy rainfall and recurrent flood in this area.

TGR in this study among the schoolchildren was found to be 44.3% (Grade 1 = 20.2% and Grade 2 = 24.1%), which indicates that we are still far from reaching the target of USI according to the WHO/ICCIDD/UNICEF recommendation. Nevertheless, many studies around the globe revealed high prevalence of goiter among the children. Rao et al. found that the goiter prevalence was 30% among schoolchildren in coastal Karnataka.[10] Chandra et al. reported 33.1% in North 24 Parganas in West Bengal.[11] Other researchers also found a high prevalence of goiter ranging from 39.5% in Metekel zone, northwest Ethiopia[14] to 36.7% in Semirom, Iran.[15] However, in the present study, we did not observe any remarkable relationship between UI excretion and goiter, which compels to think that there might be a role of other goitrogens or thyroid autoimmunity. The real picture could only be revealed after mass scale survey among children.

Wet digestion method based on Sandell–Kolthoff reaction used for UI estimation in this study is a simple, reliable, and feasible test for epidemiological studies. However, the result produced by the method cannot be considered unchallenged as the other ions can interfere the exact reading. Furthermore, care should be taken during the measurement of UI in conditions of very low and very high UI because, in such situation, the extreme values may erroneously produce similar reading.[16]

 Conclusions



Overall iodine nutrition status of children in Dhaka city is not yet up to the mark. TGR is still much higher and does not seem to be solely related to iodine nutrition status, rather other prevailing goitrogens or autoimmunity may be related. Continuous surveillance over USI is mandatory to achieve the expected satisfactory iodine nutrition status.

Financial support and sponsorship

The study was funded by the National Institute of Population Research Training (NIPORT), Bangladesh.

Conflicts of interest

There are no conflicts of interest.

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