Child mortality continues to decline, but large disparities remain

The United Nations Inter-agency Group for Child Mortality Estimation (UN-IGME) released new data last week showing that the world has made substantial progress in reducing child mortality in the last several decades. The total number of child deaths has dropped to 5.6 million in 2016 from 12.6 million in 1990. Under-five mortality rates per 1,000 live births have dropped by 56% between 1990 and 2016. If all countries achieved the average mortality of high-income countries, 87 per cent of under-five deaths could have been averted and almost 5 million lives could have been saved in 2016. The report and country-level data are available at www.childmortality.org

At current trends, 60 million children will die before their fifth birthday between 2017 and 2030, half of them newborns, according to the report released by UNICEF, the World Health Organization, the World Bank and the Population Division of UNDESA which make up the Inter-agency Group for Child Mortality Estimation (IGME).

Most newborn deaths occurred in two regions: Southern Asia (39 per cent) and sub-Saharan Africa (38 per cent). Five countries accounted for half of all new-born deaths: India (24 per cent), Pakistan (10 per cent), Nigeria (9 per cent), the Democratic Republic of the Congo (4 per cent) and Ethiopia (3 per cent).

                                                                                                                 Source: UN-IGME 2017 report

The report notes that many lives can be saved if global inequalities are  reduced. If all countries achieved the average mortality of high-income countries, 87 per cent of under-five deaths could have been averted and almost 5 million lives could have been saved in 2016.

                                                                                          Source: UN-IGME 2017 report

The United Nations Inter-agency Group for Child Mortality Estimation or UN IGME was formed in 2004 to share data on child mortality, harmonize estimates within the UN system, improve methods for child mortality estimation report on progress towards child survival goals and enhance country capacity to produce timely and properly assessed estimates of child mortality. At that time, the UN Population Division, WHO and UNICEF were all producing their own estimates of child mortality, and I was instrumental in bringing UNICEF and WHO together to share data, information and to harmonize statistics.

Some years later, the Bill and Melinda Gates Foundation funded the Institute for Health Metrics and Evaluation (IHME) at the University of Washington in Seattle, and they started to release independent estimates of child mortality. This stimulated methods improvements in both UN IGME and IHME, as well as closer examination of available data and assumptions.  While initial IHME estimates of child mortality published in 2007 concluded that child mortality was declining faster than assessed by UN-IGME (Lancet 2007, estimates from both groups have tended to converge in subsequent revisions, until this year.

According to the Global Burden of Disease (GBD) 2016 update, published in September this year (Lancet 2017 ), IHME’s most recently published estimate of child mortality for the year 2016 is just under 5 million, 642,000 deaths lower than the UN-IGME estimate.  This is a dramatic change in their assessment of global child mortality.  What is the reason for the change?

HME GBD 2016 and UN IGME estimates of the global under-five mortality rate in 2016 are actually quite similar at 38.4 deaths per 1000 live births and 40.8 respectively, as are most country estimates. The main reason in the discrepancies in the number of deaths is that different sets of estimates of live births are used by the UN IGME and IHME. UN IGME used the live birth estimates from the UN Population Division (UNPD), while IHME used its own live birth estimates. In the IHME estimates there were 128.8 million live births in 2016, 12.2 million lower than the 141 million estimated by UNPD. Previously they had also used the UNPD birth estimates, but starting from this round they have developed their own estimates.  The consequence is that the IHME number of deaths in this round (5 million) is much lower than its last round estimate. Last year IHME estimated 5.8 million under-five deaths in 2015, which is very close to the UN IGME estimate of 5.9 million.

UN IGME estimates of under-five and neonatal deaths are based on UN IGME mortality rates and UNPD estimates of the annual number of live births in each country from the World Population Prospects: the 2017 revision.  UNPD estimates of live births (like UN IGME estimates of under-five mortality) are based on a comprehensive analysis of the population dynamics and fertility levels and trends in each country taking into account all sources of data available (https://esa.un.org/unpd/wpp/DataSources/).

IHME relies on UNPD estimates of female population and age pattern of fertility for each country, but IHME estimates lower fertility levels and trends for many countries. While the information published by IHME is insufficient to fully understand all the differences, a cursory comparison suggests that about 85% of the differences in the number of live births estimates by IHME is concentrated in 25 countries (mostly in Asia and Africa) with nearly half in China and India. IHME estimates there were 11.2 million births in China in 2016, 44% lower than the 16.9 million estimated by the UN Population Division, which is quite similar to the number reported by the national Burea of Statistics of China.

Despite a very large reduction in estimated numbers of child deaths, IHME has not increased its uncertainty ranges to take into account the additional uncertainty in estimates of births.  The uncertainty range for the most recent estimate (4.8-5.2 million) is similar width to the previous IHME estimate (5.7 -6.0 million) despite the fact that there is a very substantial non-overlap between these successive revisions.

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