Abstract
To determine iodine levels in salt and iodine deficiency prevalence in school-aged children in 16 districts in Tanzania with previous severe iodine deficiency. A cross-sectional study in schoolchildren. Systematic probability sampling was used to select schools and subjects for goitre assessment and urinary iodine determination. Sixteen districts randomly selected from the 27 categorised as severely iodine-deficient in Tanzania. The study population was primary-school children aged 6-18 years who were examined for goitre prevalence and urinary iodine concentration (UIC). Salt samples from schoolchildren's homes and from shops were tested for iodine content. The study revealed that 83.3% of households (n=21,160) in the surveyed districts used iodised salt. Also, 94% of sampled shops (n=397) sold iodised salt, with a median iodine level of 37.0 ppm (range 4.2-240 ppm). Median UIC in 2089 schoolchildren was 235.0 microg l(-1) and 9.3% had UIC values below 50 microg l(-1). The overall unweighted mean visible and total goitre prevalence was 6.7% and 24.3%, respectively (n=16,222). The age group 6-12 years had the lowest goitre prevalence (3.6% visible and 18.0% total goitre, n=7147). The total goitre prevalence had decreased significantly in all districts from an unweighted mean of 65.4% in the 1980s to 24.3% in 1999 (P<0.05). We believe this difference was also biologically significant. ConclusionThese findings indicate that iodine deficiency is largely eliminated in the 16 districts categorised as severely iodine-deficient in Tanzania, and that the iodine content of salt purchased from shops is highly variable.
Highlights
Starting in 1986 iodised oil capsules (IOCs) were distributed to the 27 districts most severely affected by iodine-deficiency disorders (IDD), i.e. those with a median urinary iodine concentration (UIC) # 20 mg l21, visible goitre (3 þ 2 þ 1b) prevalence $ 10% or total goitre prevalence $ 30%4
In wholesale/retail shops, 94% of the 397 salt samples tested using test kits had iodine $15 ppm. This proportion would be considered adequate according to the World Health Organization (WHO) criterion for iodised salt sold in shops at district level[1]
This study suggests that iodine prophylaxis consistently pursued from the mid 1980s to 1999 improved iodine
Summary
Starting in 1986 IOCs were distributed to the 27 districts most severely affected by IDD, i.e. those with a median urinary iodine concentration (UIC) # 20 mg l21, visible goitre (3 þ 2 þ 1b) prevalence $ 10% or total goitre prevalence $ 30%4. The unweighted mean total goitre prevalence in the 16 districts was 24.3%, range 4.1–49.4% (Table 1).
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