Academic journal article Bulletin of the World Health Organization

Current Global Iodine Status and Progress over the Last Decade towards the Elimination of Iodine Deficiency

Academic journal article Bulletin of the World Health Organization

Current Global Iodine Status and Progress over the Last Decade towards the Elimination of Iodine Deficiency

Article excerpt

Introduction

Iodine deficiency is a major threat to the health and development of populations worldwide, particularly in preschool children and pregnant women. When requirements for iodine are not met, thyroid hormone synthesis is impaired, resulting in a series of functional and developmental abnormalities collectively referred to as iodine deficiency disorders (IDD) (1). Conditions related to iodine deficiency include goitre, stillbirth and miscarriage, hypothyroidism and impaired growth. However, the most devastating toll is from the mental and neurological disorders resulting from brain damage; preventing these is the primary motivation behind the current worldwide drive to eliminate iodine deficiency. Although cretinism is the most extreme manifestation, the more subtle degrees of mental impairment leading to poor school performance, reduced intellectual ability and impaired work capacity are of considerably greater significance (2, 3).

Universal salt iodization (USI), defined as iodization of all salt used for human and animal consumption, is the main strategy used to control iodine deficiency (4, 5). Iodine supplementation is usually restricted to areas in which severe iodine deficiency is endemic, and which have no access to iodized salt (5, 6). In most countries where iodine deficiency has been identified as a public health problem, control measures have been implemented (7). Globally, 66% of households now have access to iodized salt (8).

Until the 1990s total goitre prevalence (TGP) was used as the main indicator for assessing iodine deficiency in a population. However, TGP is of limited utility in assessing the impact of salt iodization. This is primarily because it takes a long time for goitre to disappear following the introduction of iodized salt. As urinary iodine (UI) is a more sensitive indicator of recent changes in iodine intake, this indicator is now recommended rather than TGP (5).

In 1960, WHO published the first global review on the extent of endemic goitre (9). This review, covering 115 countries, was instrumental in focusing attention on the scale of the public health problem. WHO subsequently established a global database on iodine deficiency which currently holds data from surveys conducted from the 1940s to the present day (10). Its objective is to assess the global magnitude of iodine deficiency, to evaluate the strategies for its control and to monitor each country's progress towards achieving the international community's goal of the elimination of IDD (11, 12). In 1993, using data from 121 countries, WHO published revised global estimates on the prevalence of iodine deficiency based on TGP (13). Given the increasing number of countries that have launched salt iodization programmes and conducted surveys to assess iodine status since then, updated global estimates of iodine deficiency are now considered necessary. This article presents worldwide estimates of iodine nutrition based on UI. TGP was also used to compare the current situation with the 1993 estimates (13).

Methods

Data sources--WHO Global Database on Iodine Deficiency

The WHO Global Database on Iodine Deficiency compiles country data on UI and TGP and presents them in a standardized and easily accessible format.

Data are collected from the scientific literature and through a broad network of collaborators, including WHO regional and country offices, UN organizations, nongovernmental organizations, ministries of health, other national institutions, and research and academic institutions. MEDLINE (1966-2003) and regional databases (African Index Medicus, Index Medicus for the WHO Eastern Mediterranean Region, Latin American and Caribbean Center on Health Sciences Information, Pan American Health Organization Library Institutional Memory Database and Index Medicus for the South-East Asia Region) are also systematically searched. Articles published in non-indexed medical and professional journals and reports from principal investigators are also searched. …

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