Neonatal, postneonatal, childhood, and under-5 mortality for 187 countries, 1970–2010: a systematic analysis of progress towards Millennium Development Goal 4

Summary

Background

Previous assessments have highlighted that less than a quarter of countries are on track to achieve Millennium Development Goal 4 (MDG 4), which calls for a two-thirds reduction in mortality in children younger than 5 years between 1990 and 2015. In view of policy initiatives and investments made since 2000, it is important to see if there is acceleration towards the MDG 4 target. We assessed levels and trends in child mortality for 187 countries from 1970 to 2010.

Methods

We compiled a database of 16 174 measurements of mortality in children younger than 5 years for 187 countries from 1970 to 2009, by use of data from all available sources, including vital registration systems, summary birth histories in censuses and surveys, and complete birth histories. We used Gaussian process regression to generate estimates of the probability of death between birth and age 5 years. This is the first study that uses Gaussian process regression to estimate child mortality, and this technique has better out-of-sample predictive validity than do previous methods and captures uncertainty caused by sampling and non-sampling error across data types. Neonatal, postneonatal, and childhood mortality was estimated from mortality in children younger than 5 years by use of the 1760 measurements from vital registration systems and complete birth histories that contained specific information about neonatal and postneonatal mortality.

Findings

Worldwide mortality in children younger than 5 years has dropped from 11·9 million deaths in 1990 to 7·7 million deaths in 2010, consisting of 3·1 million neonatal deaths, 2·3 million postneonatal deaths, and 2·3 million childhood deaths (deaths in children aged 1–4 years). 33·0% of deaths in children younger than 5 years occur in south Asia and 49·6% occur in sub-Saharan Africa, with less than 1% of deaths occurring in high-income countries. Across 21 regions of the world, rates of neonatal, postneonatal, and childhood mortality are declining. The global decline from 1990 to 2010 is 2·1% per year for neonatal mortality, 2·3% for postneonatal mortality, and 2·2% for childhood mortality. In 13 regions of the world, including all regions in sub-Saharan Africa, there is evidence of accelerating declines from 2000 to 2010 compared with 1990 to 2000. Within sub-Saharan Africa, rates of decline have increased by more than 1% in Angola, Botswana, Cameroon, Congo, Democratic Republic of the Congo, Kenya, Lesotho, Liberia, Rwanda, Senegal, Sierra Leone, Swaziland, and The Gambia.

Interpretation

Robust measurement of mortality in children younger than 5 years shows that accelerating declines are occurring in several low-income countries. These positive developments deserve attention and might need enhanced policy attention and resources.

Funding

Bill & Melinda Gates Foundation.

Introduction

There are only 5 years left to achieve Millennium Development Goal 4 (MDG 4), which calls for a two-thirds reduction in mortality in children younger than 5 years between 1990 and 2015. Regular assessment of levels and trends in child mortality is essential for countries to ascertain their progress towards this goal and to take action to meet it. Previous appraisals of mortality in children younger than 5 years suggest that few countries are on track to meet MDG 4.1, 2, 3 In each of these studies,1, 2, 3 no more than 26% of low-income and middle-income countries examined were deemed to be on track to reach this target. Groups such as the Countdown to 2015 Initiative³ have therefore tried to rally support to accelerate progress in child mortality.4, 5, 6, 7

The MDG 4 target has shifted the focus from tracking levels of child mortality to assessing whether countries are reducing child mortality at the 4·4% rate per year needed to achieve the two-thirds reduction in 25 years. Accurate assessments of rates of change need more robust measurement with narrower uncertainty intervals than do assessments of levels. Although there have been substantial investments in the collection of data such as summary and complete birth histories to measure child mortality, assessments of trends have varied substantially from year to year and from source to source. For example, the list of the ten countries with the fastest rates of decline in child mortality between 1990 and 2007, as reported by UNICEF in 2008,⁸ UNICEF in 2009,⁹ and the UN Population Division (UNPD) in 2009,¹⁰ have only three countries in common: Portugal, Vietnam, and the Maldives. In 2008, UNICEF reported that Thailand had the fastest rate of decline in the world, leading researchers to undertake a case study of this success.¹¹ But in 2009, UNICEF reported that Thailand had only the 47th fastest rate of decline;⁹ in a UNPD report, the country had the fourth fastest rate of decline.¹⁰ Such confusion about the true extent of progress can foster policy inaction in countries, precisely at a time when targeted, effective programmes are needed most. Variation in the assessments of rates of decline indicates the availability and use of different datasets, different analytical methods, and different decisions about data quality by the analysts.

Evidence from several low-income countries suggests that in some countries, declines in mortality in children younger than 5 years might have accelerated since 2000,12, 13, 14 whereas in others, the rate of decline might be slowing. During the 25 years of the MDG 4 target, countries are likely to experience accelerations and decelerations in rates of decline. Acceleration matters because it could be an early indication of policy or programme success. The need to use the best datasets and the most valid methods for assessing child mortality over time is only intensified when trying to detect such accelerations and decelerations. In view of the scale-up in development assistance for health,¹⁵ the expansion of insecticide-treated net coverage,¹⁶ activity of the GAVI Alliance,¹⁷ and rollout of antiretroviral drugs,¹⁸ there are many reasons to hope that accelerations might be occurring in some countries.

In this study, we examined levels, rates of decline, and accelerations and decelerations in rates of decline in neonatal, postneonatal, childhood, and under-5 mortality from 1970 to 2010 in 187 countries. This study was aided by four important developments since the previous studies were done. First, we made use of data that have been newly released or acquired during an intensive 3-year effort to obtain access to microdata (individual-level data) and tabulated data sources. Second, we used new methods to analyse data from summary birth histories with reduced bias and measurement error.¹⁹ Third, we applied new data synthesis methods with enhanced predictive validity to combine data from several sources and capture both sampling and non-sampling error patterns. This new method requires many fewer subjective inputs to estimation, ensuring that the output is strongly grounded in empirical data and is as reproducible as possible. Finally, we took advantage of more data and better models with improved predictive validity to analyse country patterns of neonatal, postneonatal, and childhood mortality.