Thyroid Research Thyroid Research Archive Iodine

Iodine deficiency is a major health problem worldwide

(March 2004)

The background of the study. Iodine deficiency is the most common cause of preventable mental retardation in the world, despite efforts to increase iodine intake in many countries. This study summarizes the results of surveys of iodine intake conducted by the World Health Organization (WHO) in many countries in the past decade.

How the study was done. Data were collected on urinary excretion of iodine in many countries from 1993 to 2003. The country-wide frequency of iodine deficiency, defined as urinary iodine excretion <100 µg/L, was then estimated. The estimates were based on the extent of sampling within the country (local, regional, or national) and the people studied (children, adults, pregnant women). The data and the details of this analysis can be seen at http://www3.who.int/whosis/micronutrient/.

The results of the study. Data on urinary iodine excretion were available from 192 countries, representing 92 percent of the world’s population. Based on worldwide population estimates for 2002, more than 1.9 billion people were iodine-deficient. They included 285 million school-age children (6 to 12 years), representing 36 percent of all school-age children.

There was considerable regional variation in the prevalence of iodine deficiency. The prevalence was lowest in the Americas (all ages, 10 percent; school-age children, 10 percent) and highest in Europe (all ages, 57 percent; school-age children, 60 percent). These rates correlate with estimates of the proportions of households in which iodized salt is consumed—90 percent in the Americas and 27 percent in Europe.

The conclusions of the study. Iodine deficiency continues to be common throughout the world.

The original article. De Benoist B, Andersson M, Takkouche B, Egli I. Prevalence of iodine deficiency worldwide. Lancet 2003;362:1859-60.

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