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

Abstract

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.

Similarities and differences of dietary and other determinants of iodine status in pregnant women from three European birth cohorts

“…In each cohort we reported both the median (25-75 th percentile) UIC (µg/L) and UI/Creat (µg/g). The percentage with UI/Creat <150 µg/g was also reported; this cut-off was informed by the WHO threshold for adequacy in pregnancy (a median UIC ≥150 µg/L) [12] and when corrected for creatinine concentration, has been used in previous research [4,6,7].…”

“…Iodine is an essential component of the thyroid hormones which are important for optimal fetal and early postnatal neurodevelopment [1,2]. Mild-to-moderate maternal iodine deficiency in early pregnancy has been associated with suboptimal offspring cognitive outcomes [3][4][5][6][7]. The early stages of pregnancy mark the beginning of crucial fetal brain development processes such as neuron proliferation, migration and differentiation [8].…”

Mild-to-Moderate Iodine Deficiency in Early Pregnancy Is Associated with Lower Verbal IQ in Children

“…Severe maternal iodine deficiency is known to be associated with low offspring IQ (1). However, the effects of mild-to-moderate maternal iodine deficiency on child neurocognitive outcomes remain poorly understood, and results of cohort studies have been somewhat variable (2)(3)(4)(5). The effects of maternal iodine status at different gestational ages on child neurodevelopment have not been examined previously.…”

The cognitive dissonance

“…Так, у когорты детей из Великобритании, рожденных от матерей с дефицитом йода (соотношение йода к креатинину ниже 150 мкг/г), был выявлен повышенный риск развития субклинических когнитивных нарушений, а уровень коэффициента интеллекта (IQ) был снижен на 3,4 пункта [4]. У австралийских детей, родившихся от матерей с уровнем йода в моче менее 150 мкг/л, в возрасте 9 лет были выявлены когнитивные расстройства, которые не компенсировались в подростковом периоде, даже несмотря на то что участники исследования уже продолжали развиваться в условиях адекватного йодного обеспечения: с 2009 года в Австралии было введено обязательное использование йодированной соли для хлебопечения [5].…”

“…Залогом эффективности этих мероприятий является то, что они направлены не специально на беременных и кормящих женщин, а на все население в целом, включая большинство женщин репродуктивного возраста. Перефразируя старый анекдот 5 , эти меры обеспечивают оптимальные уровни потребления микронутриентов "до того", так как "после того" уже не поможет даже "Боржоми".…”