Academic journal article Bulletin of the World Health Organization

The Global Burden of Diarrhoeal Disease, as Estimated from Studies Published between 1992 and 2000. (Policy and Practice)

Academic journal article Bulletin of the World Health Organization

The Global Burden of Diarrhoeal Disease, as Estimated from Studies Published between 1992 and 2000. (Policy and Practice)

Article excerpt

Introduction

Diarrhoea is one of the principal causes of morbidity and mortality among children in the developing world. In 1982, on the basis of a review of active surveillance data from studies conducted in the 1950s, 1960s and 1970s, it was estimated that 4.6 million children died annually from diarrhoea (1). In 1992, a review of studies conducted in the 1980s suggested that diarrhoeal mortality had declined to approximately 3.3 million annually (2). Both reviews estimated that children in the developing world experienced a median of between two and three episodes of diarrhoea every year. Neither review included data from China.

Since 1993 more complex methodologies have been applied to a wider range of data sources in order to estimate the global disease burden attributable to specific conditions, including diarrhoea (3-5). The strengths of recent approaches to disease burden modelling include the ability to compare figures for multiple diseases and the inclusion of the disability-adjusted life year, which takes into account both morbidity and mortality (6). However, for diseases that have been studied closely over time in many locations, such as diarrhoea among young children in developing countries, our understanding may also be deepened by a more detailed review of the most rigorously conducted studies. The purpose of the present review is to examine recent data from studies meeting the same stringent criteria as were applied in the 1982 and 1992 reviews, and to look at trends and patterns in the light of current thinking on diarrhoeal diseases and related causes of morbidity and mortality.

Methods

The studies included in this review were identified through MEDLINE searches for English language sources published since 1990 by using the following keywords: morbidity and diarrhoea; longitudinal studies and diarrhoea; mortality and diarrhoea; and verbal autopsy and diarrhoea.

Further sources were located by cross-referencing, consultation with experts in the field, and the use of the related articles link. Morbidity studies were included if active surveillance had been conducted for at least one year in a stable population of children under 5 years of age in developing countries, including China. For intervention studies, only the placebo or non-intervention group was included in the estimates. In order to allow comparison over time we utilized the methods of the two previous reviews (1, 2). Whenever possible, data were stratified by age categories (0-5 and 6-11 months, and 1,2, 3 and 4 years). Morbidity was expressed as episodes of diarrhoea per person-year. Because longitudinal data for older persons were sparse, estimates were calculated only for children aged under 5 years.

Studies were included in the mortality estimates if deaths due to diarrhoea were ascertained through active surveillance. Our estimates included prospective and retrospective studies but not ones based on vital statistics only. Death was considered to have been caused by diarrhoea only if this was listed as the primary cause. Studies that assigned equal weight to multiple causes of death were not included in the mortality estimates. If two sources described mortality rates in the same population with overlapping observation periods, only data from the more recent source were included.

Demographic data were obtained from the 1995 UNESCO estimates for countries in the following WHO regions: African, Americas, Eastern Mediterranean, South-East Asia, and Western Pacific (7). In contrast to the two earlier reviews, which excluded China from their calculations, three studies provided data from this country.

Results Morbidity

Twenty-seven studies were included in the morbidity analysis (8-38) (Table 1). The studies varied in their definitions of diarrhoea and the frequency of surveillance. One study defined diarrhoea as two or more loose stools per day; 16 studies defined it as three or more loose stools per day; three studies defined it as four or more loose stools per day; in nine studies a local definition or that of the principal caret was used. …

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