Iodine deficiency and functional performance of schoolchildren in Benin

T. van den Briel-van Ingen

Research output: Thesisinternal PhD, WU


The notion that iodine deficiency may lead not only to goiter and cretinism, but to a much wider range of disorders, from stillbirth and abortions, to hearing problems and mental and physical underdevelopment began to be accepted beyond the research community since the early 1980's. In 1990 it was estimated that these problems, collectively called iodine deficiency disorders (IDD), presented a public health problem in 118 countries and that over 40 million people were affected by some degree of mental impairment. Children who have been exposed to iodine deficiency in the pre- and early post-natal phases of life show varying degrees of mental and psychomotor retardation, depending on the duration and degree of the deficiency. Adequate maternal iodine intake before and during pregnancy prevents such disorders. The question however whether or not deficits in mental and psychomotor performance of iodine deficient children may be reversed by supple-mentation with iodine later in life has not yet been answered unequivocally.</p><p>The research described in this thesis was set up to address this question. A double-blind placebo-controlled intervention was carried out in an iodine deficient area of northern Benin in the period 1995-1996. A single oral dose of iodized oil or placebo was administrated to 2 groups of schoolchildren, aged 7-11 years. The observation period was 10-11 months. However, 3 to 4 months after supple-mentation the population started to have access to iodized salt, in addition to non-iodized salt. Because iodine became available to both groups, the main hypothesis, i.e. that iodine supplementation would improve mental performance had to be modified. It was decided to take children whose iodine status, as measured by different indicators, did not change during the observation period as the "control" group. In addition to mental and psychomotor performance, other aspects associated with iodine deficiency were studied, including behavioral change and hearing thresholds and their relation with mental performance. The suitability of several indicators for measuring iodine status and thyroid function was evaluated.</p><p>Results showed that an improvement in iodine status as measured by urinary iodine concentration, was reflected in a significantly improved performance on the combination of mental tests, 10 months after supplementation. Moreover, children with better iodine status could hear better than their peers with a poorer iodine status, while hearing thresholds were negatively correlated with performance on all mental tests, but one. The serum concentration of thyroglobulin and the urinary iodine concentration were found to be indicators most suitable for measuring change in iodine status in this age group. Although the influx of iodine into the area precludes the drawing of "hard" conclusions, the results presented suggest that iodine supplementation is likely to promote a catch-up process in functional performance of iodine deficient schoolchildren.</p>
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
  • Hautvast, J.G.A.J., Promotor
  • West, C.E., Promotor
  • Bleichrodt, N., Promotor, External person
Award date14 Dec 2001
Place of PublicationS.l.
Print ISBNs9789058085368
Publication statusPublished - 2001


  • iodine
  • deficiency
  • performance tests
  • mental ability
  • auditory threshold
  • thyroid function tests
  • school children
  • benin


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