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Mortality and Causes of Death
The second workshop session, which featured a presentation by Gilles Pison,
focused on changes in the patterns and trends of mortality and causes of death in sub-
Saharan Africa. Work done by Masquelier, Reniers, and Pison prior to the workshop
showed that, after decades of declining mortality rates in sub-Saharan Africa during the
latter half of the twentieth century, such progress is no longer the norm. Several countries
have experienced important setbacks which can be traced to such factors as political
instability, the advent or resurgence of infectious diseases, and possibly also an increase
in mortality rates from noncommunicable diseases. The lack of full-fledged vital
registration systems in most sub-Saharan countries has made it difficult to perform
detailed assessments of mortality rates. Adult mortality measurements in particular are
difficult to perform in the absence of vital registration statistics, and for that reason most
United Nations (UN) agencies estimate adult mortality by matching indices of child
survival to model age patterns of mortality.
Pison provided an overview of the trends in mortality among children under age 5
(5q0) and for individuals between the ages of 15 and 60 (45q15) in sub-Saharan Africa
which were based on data on the survival of children and siblings collected in
Demographic and Health Surveys. They used generalized additive models to smooth
mortality rates and made adjustments to correct for recall bias. Except for some
conspicuous periods of stagnation in several countries in the 1990s, child mortality
mostly declined over the past 30 to 40 years. Adult mortality patterns, by contrast, were
much more diverse. Most Eastern and Southern African countries witnessed enormous
surges in adult mortality (with 45q15 > 0.67 in some populations) that were clearly
correlated with earlier increases in HIV incidence. In Eastern Africa, adult mortality
levels have begun to decline, and, surprisingly, in some cases that happened even before
the large-scale expansion of antiretroviral therapy programs in 2005. Even more
surprising is the lack of sustained improvements in adult survival that have been observed
in some African countries without severe HIV epidemics.
Most sub-Saharan African countries have registered considerable progress in
child survival over the past 30 to 40 years but are still far removed from reaching the UN
Millennium Development Goals. Overall the region has been characterized by an
increasing convergence in mortality rates for children under age 5. Adult mortality rates
and trends are characterized by a much greater heterogeneity and sometimes move in
opposite directions from the child mortality trends in the same country. AIDS mortality is
dominating many of these all-cause mortality patterns, but the first indications of a
reversal in adult mortality rates in Eastern African countries are now visible.
During this session Pison discussed what might be learned about child mortality
from the experience of Senegal, a country with low AIDS prevalence. He noted that
Senegal experienced a rapid decrease in child mortality in the 1970s and 1980s followed
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by a period of no change in the 1990s and then a return to progress in the 2000s. The
earlier decrease was due largely to success with vaccination programs, he said, while the
lack of improvement in the 1990s can be attributed to increases in malaria mortality and
to stagnation in vaccination efforts. Renewed efforts to combat malaria (new treatments,
rapid diagnostic tests, and impregnated bed nets) and progress in vaccine coverage were
largely responsible for the resumption of the decline in mortality during the past decade.
The presenters acknowledged that improvements in socioeconomic conditions might also
have had an influence, but the results of that influence would be visible only over the
long term and would not explain relatively rapid changes such as the mortality decline in
the 2000s. A key takeaway point of the session was that vaccinations and efforts to
combat malaria have "non-specific" effects, meaning that in addition to lowering
mortality due to the specific disease being addressed, they also tend to lower mortality
due to other causes.
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