( 0 M M 0 N (A N ( E R S: B REA S T,P R 0 S TATE I l A R G E BOW Ell 69
GEOGRAPHIC DISPARITY
North America, Europe, Australia and wealthier Asian countries Qa-
pan, Singapore) have very high rates of colorectal cancer, while Africa,
Asia and most of Central and South America have very low rates of this
cancer. For example, the Czech Republic has a death rate of 34.19 per
100,000 males, while Bangladesh has a death rate of 0.63 per 100,000
males! 62 ,63 Chart 8.3 shows a comparison of average death rates between
more developed countries and less developed countries; all these rates
are age-adjusted.
The fact that rates of colorectal cancer vary hugely between countries
has been known for decades. The question has always been why. Are the
differences due to genetics, or to environment?
It seems that environmental factors, including diet, play the most
important roles in colorectal cancer. Migrant studies have shown that
as people move from a low-cancer risk area to a high-cancer risk area,
they assume an increased risk within two generations.^64 This suggests
that diet and lifestyle are important causes of this cancer. Other stud-
ies have also found that rates of colorectal cancer change rapidly as a
population's diet or lifestyle changes.^64 These rapid changes in cancer
rates within one population cannot possibly be explained by changes in
inherited genes. In the context of human society, it takes thousands of
CHART 8.3: COLORECTAL CANCER DEATH RATE IN "MORE
DEVELOPED" COUNTRIES AND "LESS DEVELOPED" COUNTRIES18
Death^16
Rate per^14
100,000^12
People^10
(age-^8
adjusted)^6
4
2
0
More
Developed
CountriesLess
Developed
Countries.Male
[J Female