Huda, Syed Nazmul; (1998) Iodine nutrition, cognition and school achievement of Bangladeshi school children. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Two studies were conducted concerning the association between iodine deficiency and levels of school achievement, cognition and motor skills in Bangladeshi school children. In 3 rural, severely iodine-deficient areas, 2003 children were screened for T4 and TSH. 170 children with T4 <45 nmol/L (hypothyroid) were identified and compared with 170 children with T4 >70 nmol/L (euthyroid), matched for school and grade on the following: Wide Range Achievement Test, 8 cognitive function and 3 fine motor function tests, anthropometry and social background. The hypothyroid children performed worse than the euthyroid children on reading and spelling and in one cognitive function test. A factor analysis of cognitive and motor function tests yielded 2 factors, a general cognitive and a fine motor one. There was a significant difference between the groups in the general cognitive factor, after controlling for socio-cultural and biological variables. Parental education, food deprivation, household possessions and home stimulation made significant independent contributions to the children's development. An unplanned increase in T4 levels occurred in all groups between the time of screening and enrolment, though urinary iodine measures remained moderately deficient. A double-blind placebo-controlled trial was conducted with 305 hypothyroid children (screening T4 <51 nmol/L) and 304 euthyroid children (T4 >60 nmol/L). Four months after treatment, urinary iodine levels improved in the iodine- treated group, but there was no effect on T4 or TSH. No benefit was observed on any cognitive function test. Post-hoc analyses showed that change in T4 levels was significantly associated with changes in two cognitive function tests and one fine motor function test. The results of the case-control study suggest that iodine deficiency associated with hypothyroidism detrimentally affects school achievement and cognition. However, the treatment trial indicates that children with moderate iodine deficiency in the presence of normal T4 may not benefit in these functions from IPSO treatment.

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