Reduced Educational Outcomes Persist into Adolescence Following Mild Iodine Deficiency in Utero, Despite Adequacy in Childhood: 15-Year Follow-Up of the Gestational Iodine Cohort Investigating Auditory Processing Speed and Working Memory

There is increasing evidence that even mild gestational iodine deficiency (GID) results in adverse neurocognitive impacts on offspring. It’s unclear, however, if these persist long-term and whether they can be ameliorated by iodine sufficiency in childhood. We followed a unique cohort (Gestational Iodine Cohort, n = 266) where gestation occurred during a period of mild population iodine deficiency, with children subsequently growing-up in an iodine replete environment. We investigated whether associations between mild GID and reductions in literacy outcomes, observed at age 9-years, persisted into adolescence. Comparisons were made between offspring of mothers with gestational urinary iodine concentrations (UICs) ≥ 150 μg/L and < 150 μg/L. Educational outcomes were measured using Australian National Assessment Program—Literacy and Numeracy (NAPLAN) tests. Children whose mothers had UICs < 150 μg/L exhibited persistent reductions in spelling from Year 3 (10%, −41.4 points (95% Confidence Interval −65.1 to −17.6, p = 0.001)) to Year 9 (5.6%, −31.6 (−57.0 to −6.2, p = 0.015)) compared to children whose mothers had UICs ≥ 150 μg/L. Associations remained after adjustment for biological factors, socioeconomic status and adolescent UIC. Results support the hypothesis that mild GID may impact working memory and auditory processing speed. The findings have important public health implications for management of iodine nutrition in pregnancy

Women Remain at Risk of Iodine Deficiency during Pregnancy: The Importance of Iodine Supplementation before Conception and Throughout Gestation

In Australia, pregnant women are advised to take an iodine supplement (I-supp) (150 µg/day) to reduce risks to the foetus associated with iodine deficiency (ID). To examine the impact of this recommendation on iodine status, and to identify factors that contribute to adequacy during gestation, supplement use and Urinary Iodine Concentration (UIC) was measured in 255 pregnant women (gestation range 6 to 41 weeks) in Tasmania. The median UIC (MUIC) of 133 µg/L (Inter-quartile range 82–233) was indicative of ID, being below the 150–249 µg/L range for adequacy during pregnancy. Women taking an iodine-containing-supplement (I-supp) had a significantly higher MUIC (155 µg/L) (n = 171) compared to the combined MUIC (112.5 µg/L) (n = 84) of those who had never (120 µg/L) (n = 61) or were no longer taking an I-supp (90 µg/L) (n = 23) (p = 0.017). Among women reporting I-supp use, the MUIC of those commencing the recommended 150 µg/day prior to conception was significantly higher than those starting supplementation following pregnancy confirmation: 196 (98–315) µg/L (n = 45) versus 137.5 (82.5–233.5) µg/L (n = 124), p = 0.032. Despite recommendations for iodine supplementation pregnant Tasmanian women remain at risk of ID. Commencing an I-supp of 150 µg/day prior to conception and continuing throughout pregnancy is required to ensure adequacy. Timely advice regarding the importance of adequate iodine nutrition, including supplementation is needed to reduce the risk of irreversible in utero neurocognitive damage to the foetus

Persistent iodine deficiency in a cohort of Tasmanian school children: associations with socio‐economic status, geographical location and dietary factors

Abstract Objective: To determine the adequacy of iodine nutrition of Tasmanian primary school‐aged children and to examine possible associations with socio‐economic status (SES), location and dietary factors. Methods: Urinary iodine levels and measures of SES, geographical information and dietary habits were surveyed in a population‐based sample of 170 children (4 to 12 years) at baseline (1998/99) and at follow‐up (2000/01). Results: Median urinary iodine concentration in 1989‐99 and 2000‐01 were 75 μg/L (range 15 μg/L to 240 μg/L) and 76 μg/L (range 18 μg/L to 480 μg/L) respectively. No significant associations with SES or geographical location were found. More frequent or recent intake of foods that are likely to be dietary sources of iodine tended to be associated with greater prevalence of adequate urinary iodine, particularly consumption of yoghurt and ‘fruche’ (p=0.04). Conclusions: After several decades of iodine sufficiency, Tasmanian primary school‐aged children are again mildly iodine‐deficient by WHO criteria. Despite reduction in iodophor use by the dairy industry in the past decade, consumption of dairy products continues to be associated with higher levels of iodine nutrition. Implications: The lack of association of iodine levels with SES and geographical location within Tasmania found in our study, and the results of studies of iodine levels in Melbourne and Sydney, suggest that inadequate iodine nutrition is a widespread problem in south‐eastern Australia. Our study suggests that milk‐containing products continue to be an important source of iodine for children