The China Study by Thomas Campbell

76 THE CHINA STUDY

could include a variety of possibilities, ranging from the geographic

and environmental to the biological. However, because all diseases are

biological processes (gone awry), we can assume that whatever "causes"

are observed, they will eventually operate through biological events.

When these diseases were cross-listed in a way that allowed every

disease rate to be compared with every other disease rate,9 two groups

of diseases emerged: those typically found in more economically de-

veloped areas (diseases of affluence) and those typically found in rural

agricultural areas (diseases of poverty) 10 (Chart 4.4).

CHART 4.4. DISEASE GROUPINGS OBSERVED IN RURAL CHINA

Diseases of Affluence Cancer (colon, lung, breast, leukemia,

(Nutritional Extravagance) childhood brain, stomach, liverL diabe-

tes, coronary heart disease

Diseases of Poverty (Nutritional Pneumonia, intestinal obstruction,

inadequacy and poor sanitation) peptic ulcer, digestive disease,

pulmonary tuberculosis, parasitic dis-

ease, rheumatic heart disease, meta-

bolic and endocrine disease other than

diabetes, diseases of pregnancy and

many others

Chart 4.4 shows that each disease, in either list, tends to associate
with diseases in its own list but not in the opposite list. A region in
rural China that has a high rate of pneumonia, for example, will not
have a high rate of breast cancer, but will have a high rate of a parasitic
disease. The disease that kills most Westerners, coronary heart disease,
is more common in areas where breast cancer also is more common.
Coronary heart disease, by the way, is relatively uncommon in many
developing societies of the world. This is not because people die at a
younger age, thus avoiding these Western diseases. These comparisons
are age-standardized rates, meaning that people of the same age are be-
ing compared.
Disease associations of this kind have been known for quite some time.
What the China Study added, however, was an unsurpassed amount of
data on death rates for many different diseases and a unique range of di-
etary experience. As expected, certain diseases do cluster together in the
same geographic areas, implying that they have shared causes.
These two disease groups have usually been referred to as diseases of