Combining health and social protection measures to reach the ultra ...

Decision-making
Inequities in health status:
findings from the 2001 Global
Burden of Disease study
Article by Alan Lopez (pictured) and Colin Mathers
The 1990 Global Burden of Disease (GBD) study
developed a comprehensive framework for integrating,
validating, analyzing, and disseminating fragmented
information on the health of populations so that it is truly
useful for health policy and planning 7 . Features of this
framework included the incorporation of data on nonfatal
health outcomes into summary measures of population
health (described in the next subsection), the development of
methods and approaches to estimate missing data and to
assess the reliability of data, and the use of a common metric
to summarize the disease burden both from diagnostic
categories of the international classification of diseases (ICD)
and the major risk factors that cause those health outcomes.
The basic philosophy guiding the burden of disease
approach is that almost all sources of health data are likely to
have information content provided that they are carefully
screened for plausibility and completeness and that internally
consistent estimates of the global descriptive epidemiology of
major conditions are possible with appropriate tools,
investigator commitment, and expert opinion. This
philosophy remains central to the GBD 2001 study, which
has expanded the framework of the original GBD study to:
✜ quantify the burden of premature mortality and disability
by age, sex, and region for 135 major causes or groups
of causes;
✜ develop internally consistent estimates of incidence,
prevalence, duration, and case fatality rates for more
than 500 sequelae resulting from the foregoing causes;
✜ analyze the contribution to this burden of major
physiological, behavioural, and social risk factors by age,
sex, and region.
Estimating mortality: methods and data
Complete death registration data cover only one third of the
world’s population. Some information on another third is
available through the national sample registration systems
and urban death registration systems of India and China. For
the remaining one third of the world’s population, including
most countries in sub-Saharan Africa, only partial information
is available from epidemiological studies, disease registers,
and surveillance systems.
To estimate the number of deaths by cause we drew on the
following four broad sources of data:
✜ Death registration systems. Complete or incomplete
death registration systems provide information about
causes of death for almost all high-income countries
and for many countries in Europe (Eastern) and Central
Asia and in Latin America and the Caribbean. Some
vital registration information is also available in all
other regions.
✜ Sample death registration systems. In China and India,
sample registration systems for rural areas supplement
urban death registration systems. Information systems
now provide information on causes of death for several
other large countries for which information was not
available at the time of the original GBD study.
✜ Epidemiological assessments. Epidemiologists have
estimated deaths for specific causes, such as HIV/AIDS,
malaria, and tuberculosis (TB), for most countries in the
regions most affected. These estimates usually combine
information from surveys on the incidence or prevalence
of the disease with data on case fatality rates.
✜ Cause of death models. The cause of death models used
in the original GBD study 7 were substantially revised and
enhanced for estimating deaths by broad cause group in
regions with limited information on mortality. The
CodMod software developed for this study and described
later drew on a data set of 1613 country-years of
observation of cause of death distributions from 58
countries between 1950 and 2001.
For the GBD 2001 study, age- and sex-specific death rates
were calculated from the death and population data provided
by countries, with adjustments made for completeness of the
registration data where needed, and then total deaths by age
and sex were calculated for each country by applying these
rates to the United Nations Population Division estimates of
de facto populations for 2001.
Four methods were used to construct life tables for each
country depending on the type of data available 2 :
✜ Countries with death registration data for 2001. Such
data were used directly to construct life tables for 56
countries after adjusting for incomplete registration if
necessary.
✜ Countries with a time series of death registration data.
Where the latest year of death registration data available
Global Forum Update on Research for Health Volume 4 ✜ 163