History of Iodine Deficiency in Schoolchildren in Tasmania, Australia

Introduction: The island State of Tasmania, in Australia, has long been recognized as an area of endemic iodine deficiency. This chapter reviews the history of iodine deficiency, supplementation and monitoring of school age children in the state. The history of iodine nutrition from 1949, when the first survey and supplementation program was undertaken, to the late 1980s when the population was considered to be iodine sufficient is reviewed. Details of the surveys conducted to confirm the re-emergence of iodine deficiency following a period without regular monitoring are presented. And the outcomes of a subsequent voluntary program of bread fortification and a series of post-fortification urinary iodine surveys are discussed. The need for a sustainable form of iodine prophylaxis, preferably universal salt iodization, is proposed. Recent Surveys of Iodine in Tasmania: Six cross-sectional urinary iodine surveys were conducted on Tasmanian schoolchildren. The first two surveys (1998¨C1999 and 2000¨C2001) were conducted to determine the status of urinary iodine levels in a representative sample of children following more than a decade without monitoring. In addition to urinary iodine measurement, data were collected on the age, sex and school of each participant. The school they attended was assigned a residential category, a geographical classification and a number of socioeconomic status (SES) scores. Parental education, employment status, and occupation were recorded; a food frequency questionnaire (FFQ) was completed; and a range of questions about the frequency and recency of consumption of iodine-containing foods was asked. Following voluntary fortification of bread, a series of four postintervention surveys were conducted in 2003, 2004, 2005 and 2007. Urinary iodine measurements were made and the sex and school of each participant was recorded. As with the pre-intervention surveys, each school was assigned a residential category, a geographical classification and three SES scores. Summary of Survey Findings: Results for children aged 8¨C11 years are presented. For both the pre-intervention surveys (1998¨C1999 and 2000¨C2001) the urinary iodine concentrations (UIC), based on the World Health Organization (WHO) definitions, were indicative of mild iodine deficiency. The combined overall median UIC pre-intervention was 77.5 «°g/l. Seventy-five percent of the children had UIC less than 100 «°g/l. This was in excess of the WHO recommendation that no more than 50% of a population-based sample should have concentrations below 100 «°g/l. Only 15.7% of the children, however, had UIC less than 50 «°g/ l. This was within the WHO recommendation of no more than 20% below this concentration. Following fortification, the median UIC of schoolchildren examined in the four post-intervention surveys improved significantly (108 «°g/l, P ªÍ 0.0001). Using the WHO definitions, the postintervention UIC increased to a level indicative of optimal iodine nutrition and reflecting adequate iodine intake. The percentage of children with UIC less than 100 «°g/l and 50 «°g/l was less than 50% and 20%, respectively, for all post-intervention surveys. However, subgroups analysis revealed that while boys were iodine sufficient (median UIC 123.0 «°g/l), girls bordered on insufficiency (median UIC 99.0 «°g/l). In both the pre- and post-intervention surveys there were no compelling associations found between UIC and any of the SES indicators. Children from private schools had similar median UIC to those from public schools. All three school-based ratings of SES were only weakly, but not statistically significantly, associated with UIC. And UIC was not associated with either maternal or paternal education, employment status, or occupation. Categorization of schools into rural, semirural and urban locations did not reveal any association with UIC. Examination of geographical locations, which had