Improved iodine status is associated with improved mental performance of schoolchildren in Benin.

BACKGROUND: An adequate iodine supply in utero and shortly after birth is known to be crucial to an individual's physical and mental development. The question of whether iodine supplementation later in life can exert a favorable influence on the mental performance of iodine-deficient populations was addressed in various studies, but with contradictory results. OBJECTIVE: The aim of this study was to examine the effect of an improvement in iodine status on mental and psychomotor performance of schoolchildren (7-11 y) who were moderately to severely iodine deficient. DESIGN: The study, which was originally planned as a double-blind, randomized, placebo-controlled intervention, was carried out in an iodine-deficient population of schoolchildren (n = 196) in northern Benin. As the population began to have access to iodized salt during the 1-y intervention period, the study population was split post hoc-on the basis of urinary iodine concentrations-into a group with improved iodine status and a group with unchanged iodine status. Changes in mental and psychomotor performance over the intervention period were compared. RESULTS: Children with increased urinary iodine concentrations had a significantly greater increase in performance on the combination of mental tests than did the group with no change in urinary iodine concentrations. CONCLUSIONS: An improvement in iodine status, rather than iodine status itself, determined mental performance in this population, which was initially iodine deficient. These findings suggest a "catch-up" effect in terms of mental performance.

Twin-singleton differences in intelligence?

The twin method has been criticised for its alleged non-generalisability. When population parameters of intellectual abilities are estimated from a twin sample, critics point to the twin-singleton differences in intrauterine and family environments. These differences are suggested to lead to suboptimal cognitive development in twins. Although previous studies have reported twin-singleton differences in intelligence, these studies had two major drawbacks: they tested young twins, and twins were compared with (genetically) unrelated singletons. To test accurately whether twin-singleton differences in intelligence exist, a group of adult twins and their non-twin siblings were administered the Dutch WAIS-III. The group was large enough to detect twin-singleton differences of magnitudes reported in earlier investigations. The data were analysed using maximum likelihood model fitting. No evidence of differences between adult twins and their non-twin siblings on cognitive performance was found. It is concluded that twin studies provide reliable estimates of heritabilities of intellectual abilities which can be generalised to the singleton population.

Absence of neuropsychological sequelae following cerebral malaria in Gambian children.

Cerebral malaria causes major neurological sequelae in a proportion of survivors and may lead to neuropsychological sequelae in children who seem to have made a good recovery. If this is the case, cerebral malaria could have a dramatic impact on the development of thousands of African children. The present study was carried out to provide information on the incidence and type of neuropsychological sequelae in children who survive the disease without major neurological sequelae. A matched case-control study design was used in which 36 pairs of children were assessed. The cases had been treated for cerebral malaria a mean of 3.4 years before testing. No evidence of a serious long-term impact on most assessed neuropsychological functions was found in these children. Only in the balance test did cases perform less well than their matched controls, but the difference between the 2 groups was only of borderline significance. These findings suggest that the long-term impact of cerebral malaria on the development of children who recover without major neurological sequelae is not as serious as had been feared.

Effects of iodine deficiency on mental and psychomotor abilities.

Severe iodine deficiency may lead to endemic cretinism, which is characterized by a number of abnormalities, such as mental retardation, neurological abnormalities and hearing disorders. These abnormalities may occur in various combinations, but impaired mental development is always a component. The present study was attempted to determine whether there is also evidence of mental retardation, perhaps to a lesser degree, in that part of the population that manifest no symptoms of cretinism, the non-cretins, in an iodine-deficient area. Results of an extensive test battery have been collected in two village populations: one village in an area with severe iodine deficiency and a control village in a non-iodine-deficient area. Both villages were situated in Central Java, Indonesia. In the selected villages the total population between the ages of 6 and 20 years participated in this study. No evidence of significant mental retardation has been detected in the non-cretin group in the severely iodine-deficient area. Significant differences between the two populations, however, have been found with regard to a number of perceptual and neuro-motor abilities.