Abstract
BackgroundIn many low-income countries, children are at high risk of iodine deficiency disorders, including brain damage. In the early 1990s, Tanzania, a country that previously suffered from moderate to severe iodine deficiency, adopted universal salt iodation (USI) as an intervention strategy, but its impact remained unknown.MethodsWe report on the first national survey in mainland Tanzania, conducted in 2004 to assess the extent to which iodated salt was used and its apparent impact on the total goitre prevalence (TGP) and urinary iodine concentrations (UIC) among the schoolchildren after USI was initiated. In 2004, a cross-sectional goitre survey was conducted; covering 140,758 schoolchildren aged 6 - 18 years were graded for goitre according to new WHO goitre classification system. Comparisons were made with district surveys conducted throughout most of the country during the 1980s and 90s. 131,941 salt samples from households were tested for iodine using rapid field test kits. UIC was determined spectrophotometrically using the ammonium persulfate digestion method in 4523 sub-sampled children.Results83.6% (95% CI: 83.4 - 83.8) of salt samples tested positive for iodine. Whereas the TGP was about 25% on average in the earlier surveys, it was 6.9% (95%CI: 6.8-7.0) in 2004. The TGP for the younger children, 6-9 years old, was 4.2% (95%CI: 4.0-4.4), n = 41,965. In the 27 goitre-endemic districts, TGP decreased from 61% (1980s) to 12.3% (2004). The median UIC was 204 (95% CF: 192-215) μg/L. Only 25% of children had UIC <100 μg/L and 35% were ≥ 300 μg/L, indicating low and excess iodine intake, respectively.ConclusionOur study demonstrates a marked improvement in iodine nutrition in Tanzania, twelve years after the initiation of salt iodation programme. The challenge in sustaining IDD elimination in Tanzania is now two-fold: to better reach the areas with low coverage of iodated salt, and to reduce iodine intake in areas where it is excessive. Particular attention is needed in improving quality control at production level and perhaps the national salt iodation regulations may need to be reviewed.
Highlights
In many low-income countries, children are at high risk of iodine deficiency disorders, including brain damage
In mainland Tanzania, 41% of the population live in geographic areas subjected to iodine-deficiency [6], and many scattered surveys conducted around the country during the 1980s showed that an estimated 25% suffered from some form of iodine deficiency disorders (IDD) [7]
This paper presents the results from the first national survey in mainland Tanzania, conducted in 2004 to assess the extent of iodated salt use, to measure urinary iodine concentrations (UIC), and to estimate total goitre prevalence (TGP) among schoolchildren approximately twelve years after salt iodation was initiated in Tanzania
Summary
In many low-income countries, children are at high risk of iodine deficiency disorders, including brain damage. Lack of iodine at conception causes maternal hypothyroidism, which has dramatic consequences for the foetus, leading to severe and irreversible brain damage These consequences can be prevented by the correction of iodine deficiency (ID) before pregnancy [2] through iodated salt (I-salt) or iodine supplements to pregnant and lactating women [3]. In some areas in the Southern Highlands, the total goitre prevalence (TGP) reached as high as 90% and half the school children were hypothyroid [8]. These areas were among the 27 districts targeted for iodized oil capsules, which were provided biannually to everyone 1-45 years old from 1985 [9]. As universal salt iodation (USI) was satisfactorily implemented, gradually the capsules were phased out in 1996 [10]
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