Global, regional, and national age-sex-specific mortality and life expectancy, 1950-2017:
a systematic analysis for the Global Burden of Disease Study 2017. 

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Abstract

BACKGROUND:Assessments of age-specific mortality and life expectancy have been done
by the UN Population Division, Department of Economics and Social Affairs (UNPOP),
the United States Census Bureau, WHO, and as part of previous iterations of the Global
Burden of Diseases, Injuries, and Risk Factors Study (GBD).  Previous iterations of
the GBD used population estimates from UNPOP, which were not derived in a way that
was internally consistent with the estimates of the numbers of deaths in the GBD. 
The present iteration of the GBD, GBD 2017, improves on previous assessments and provides
timely estimates of the mortality experience of populations globally.  METHODS:The
GBD uses all available data to produce estimates of mortality rates between 1950 and
2017 for 23 age groups, both sexes, and 918 locations, including 195 countries and
territories and subnational locations for 16 countries.  Data used include vital registration
systems, sample registration systems, household surveys (complete birth histories,
summary birth histories, sibling histories), censuses (summary birth histories, household
deaths), and Demographic Surveillance Sites.  In total, this analysis used 8259 data
sources.  Estimates of the probability of death between birth and the age of 5 years
and between ages 15 and 60 years are generated and then input into a model life table
system to produce complete life tables for all locations and years.  Fatal discontinuities
and mortality due to HIV/AIDS are analysed separately and then incorporated into the
estimation.  We analyse the relationship between age-specific mortality and development
status using the Socio-demographic Index, a composite measure based on fertility under
the age of 25 years, education, and income.  There are four main methodological improvements
in GBD 2017 compared with GBD 2016: 622 additional data sources have been incorporated;
new estimates of population, generated by the GBD study, are used; statistical methods
used in different components of the analysis have been further standardised and improved;
and the analysis has been extended backwards in time by two decades to start in 1950. 
FINDINGS:Globally, 18·7% (95% uncertainty interval 18·4-19·0) of deaths were registered
in 1950 and that proportion has been steadily increasing since, with 58·8% (58·2-59·3)
of all deaths being registered in 2015.  At the global level, between 1950 and 2017,
life expectancy increased from 48·1 years (46·5-49·6) to 70·5 years (70·1-70·8) for
men and from 52·9 years (51·7-54·0) to 75·6 years (75·3-75·9) for women.  Despite this
overall progress, there remains substantial variation in life expectancy at birth
in 2017, which ranges from 49·1 years (46·5-51·7) for men in the Central African Republic
to 87·6 years (86·9-88·1) among women in Singapore.  The greatest progress across age
groups was for children younger than 5 years; under-5 mortality dropped from 216·0
deaths (196·3-238·1) per 1000 livebirths in 1950 to 38·9 deaths (35·6-42·83) per 1000
livebirths in 2017, with huge reductions across countries.  Nevertheless, there were
still 5·4 million (5·2-5·6) deaths among children younger than 5 years in the world
in 2017.  Progress has been less pronounced and more variable for adults, especially
for adult males, who had stagnant or increasing mortality rates in several countries. 
The gap between male and female life expectancy between 1950 and 2017, while relatively
stable at the global level, shows distinctive patterns across super-regions and has
consistently been the largest in central Europe, eastern Europe, and central Asia,
and smallest in south Asia.  Performance was also variable across countries and time
in observed mortality rates compared with those expected on the basis of development. 
INTERPRETATION:This analysis of age-sex-specific mortality shows that there are remarkably
complex patterns in population mortality across countries.  The findings of this study
highlight global successes, such as the large decline in under-5 mortality, which
reflects significant local, national, and global commitment and investment over several
decades.  However, they also bring attention to mortality patterns that are a cause
for concern, particularly among adult men and, to a lesser extent, women, whose mortality
rates have stagnated in many countries over the time period of this study, and in
some cases are increasing.  FUNDING:Bill & Melinda Gates Foundation. 

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Assistant Professor of Environmental Health Science at Duke Kunshan University

My research interest is in the intersection of environment and population health. 
Trained as an environmental epidemiologist, I am primarily interested in environmental
determinants of longevity.  Second, given populations are living longer, how can we
delay neuro-degeneration and age-related diseases.  Third, I am a proponent in applying
research for better policy-making to achieve SDG targets.