THE EPIDEMIOLOGIC TRANSITION–CHANGES IN THE BURDEN OF DISEASE AND RISK FACTORS

The secular improvements in ages at death have been accompanied by changes in causes of death. In
the broadest terms, the proportion of deaths due to infectious disease and conditions associated with
pregnancy and delivery has fallen, and the proportion due to chronic, noncommunicable diseases, such
as heart and cerebrovascular diseases, diabetes, cancers, and age-related neurodegenerative
diseases such as Alzheimer's and Parkinson's diseases, has increased steadily and is expected to
continue to increase. Figure 70-5 shows results from an international comparative project that drew on

a wide variety of data sources to provide estimates of the global burden of disease at the beginning of
this century, with projections to future years based on recent trends in disease prevalence and
demographic rates. Burden of disease in these pie charts is a composite measure, one that takes into
account both the number of deaths due to a particular disease or condition and the timing of such
deaths—an infant death represents a loss of more potential life-years lived than does the death of a
very old person. Nor is death the only outcome that matters; most diseases or conditions cause
significant disability and suffering even when nonfatal, so this measure of burden captures nonfatal
outcomes using statistical weighting. As Table 70–3 shows, the "modern plagues" of chronic
noncommunicable diseases are already among the leading causes of premature death and disability
even in low-income countries. This is due to a mix of factors—lower fertility rates mean fewer infants
and children at prime ages of susceptibility to infections; more people reaching older ages when chronic
disease incidence is high; and often changing incidence rates due to increased exposure to tobacco,
Western diets, and inactivity. Noncommunicable diseases, once thought of as "diseases of affluence"
—are projected to account for more than half of the disease burden even in low- and middle-income
countries by the year 2030 (Fig. 70-5).
Figure 70-5
Leading causes of burden of illness in world regions 2002 and projected for 2030. (Adapted from
Mathers and Loncar.)