Gaps in policy-relevant information on burden of disease in children: a systematic review.

BACKGROUND: Valid information about cause-specific child mortality and morbidity is an essential foundation for national and international health policy. We undertook a systematic review to investigate the geographical dispersion of and time trends in publication for policy-relevant information about children's health and to assess associations between the availability of reliable data and poverty. METHODS: We identified data available on Jan 1, 2001, and published since 1980, for the major causes of morbidity and mortality in young children. Studies with relevant data were assessed against a set of inclusion criteria to identify those likely to provide unbiased estimates of the burden of childhood disease in the community. FINDINGS: Only 308 information units from more than 17,000 papers identified were regarded as possible unbiased sources for estimates of childhood disease burden. The geographical distribution of these information units revealed a pattern of small well-researched populations surrounded by large areas with little available information. No reliable population-based data were identified from many of the world's poorest countries, which account for about a third of all deaths of children worldwide. The number of new studies diminished over the last 10 years investigated. INTERPRETATION: The number of population-based studies yielding estimates of burden of childhood disease from less developed countries was low. The decreasing trend over time suggests reductions in research investment in this sphere. Data are especially sparse from the world's least developed countries with the highest child mortality. Guidelines are needed for the conduct of burden-of-disease studies together with an international research policy that gives increased emphasis to global equity and coverage so that knowledge can be generated from all regions of the world.

Predicting the distribution of under-five deaths by cause in countries without adequate vital registration systems.

BACKGROUND: The absence of complete vital registration and atypical nature of the locations where epidemiological studies of cause of death in children are conducted make it difficult to know the true distribution of child deaths by cause in developing countries. A credible method is needed for generating valid estimates of this distribution for countries without adequate vital registration systems. METHODS: A systematic review was undertaken of all studies published since 1980 reporting under-5 mortality by cause. Causes of death were standardized across studies, and information was collected on the characteristics of each study and its population. A meta-regression model was used to relate these characteristics to the various proportional mortality outcomes, and predict the distribution in national populations of known characteristics. In all, 46 studies met the inclusion criteria. RESULTS: Proportional mortality outcomes were significantly associated with region, mortality level, and exposure to malaria; coverage of measles vaccination, safe delivery care, and safe water; study year, age of children under surveillance, and method used to establish definitive cause of death. In sub-Saharan Africa and in South Asia, the predicted distribution of deaths by cause was: pneumonia (23% and 23%), malaria (24% and <1%), diarrhoea (22% and 23%), 'neonatal and other' (29% and 52%), measles (2% and 1%). CONCLUSIONS: For countries without adequate vital registration, it is possible to estimate the proportional distribution of child deaths by cause by exploiting systematic associations between this distribution and the characteristics of the populations in which it has been studied, controlling for design features of the studies themselves.

Methodological and quality issues in epidemiological studies of acute lower respiratory infections in children in developing countries.

Acute respiratory infections are the most important single cause of global burden of disease in young children globally and a major cause of child mortality. A recent review of studies reporting the incidence of acute lower respiratory infections (ALRI) in young children in the developing world was carried out by the WHO Child Health Epidemiology Reference Group in order to inform global burden of disease estimates. The review highlighted the low number of community-based longitudinal studies of ALRI incidence in young children which met minimum quality criteria. It underscored the need to give attention to issues of study design and the reporting of a basic minimum dataset which describes circumstances under which the studies were being conducted and the key design features of the study which may influence the ALRI estimate. This paper aims to provide methodological guidelines for the design, conduct, and reporting of epidemiological studies of ALRI in under-5s in developing countries. It discusses determinants of study quality related to both study design and statistical analysis and also issues requiring further research. It is hoped that these guidelines will stimulate further work in this field and encourage the publication of reports which contain sufficient data to permit a meaningful meta-analysis of the data, thus forming the basis of more reliable future estimates of global burden of ALRI.

Global estimate of the incidence of clinical pneumonia among children under five years of age.

OBJECTIVE: Clinical pneumonia (defined as respiratory infections associated with clinical signs of pneumonia, principally pneumonia and bronchiolitis) in children under five years of age is still the leading cause of childhood mortality in the world. In this paper we aim to estimate the worldwide incidence of clinical pneumonia in young children. METHODS: Our estimate for the developing world is based on an analysis of published data on the incidence of clinical pneumonia from community based longitudinal studies. Among more than 2000 studies published since 1961, we identified 46 studies that reported the incidence of clinical pneumonia, and 28 of these met pre-defined quality criteria. FINDINGS: The estimate of the median incidence from those studies was 0.28 episodes per child-year (e/cy). The 25-75% interquartile range was 0.21-0.71. We assessed the plausibility of this estimate using estimates of global mortality from acute respiratory infections and reported case fatality rates for all episodes of clinical pneumonia reported in community-based studies or the case-fatality rate reported only for severe cases and estimates of the proportion of severe cases occurring in a defined population or community. CONCLUSION: The overlap between the ranges of the estimates implies that a plausible incidence estimate of clinical pneumonia for developing countries is 0.29 e/cy. This equates to an annual incidence of 150.7 million new cases, 11-20 million (7-13%) of which are severe enough to require hospital admission. In the developed world no comparable data are available. However, large population-based studies report that the incidence of community-acquired pneumonia among children less than five years old is approximately 0.026 e/cy, suggesting that more than 95% of all episodes of clinical pneumonia in young children worldwide occur in developing countries.