Someone wrote:
>When one is looking at breast cancer rates
>in relation to breastfeeding or any other factors,
>it is also important to include average life span.
>I don't have exact statistics at my finger tips,
>but I think that a good deal of breast cancer
>in the U.S. occurs in older women. Average
>life span of women in China may explain a lot of
>the difference in breast cancer rates.

Life span has nothing to do with breast cancer rates.  Typical life span is
the same in all contemporary human cultures, and has remained unchanged for
at least the past 100,000 years, and probably farther back, and is likely to
remain unchanged for the forseeable future.

What is different between different regions of the world is *average life
expectancy at birth,* which is calculated by adding up the ages at death and
dividing by the number of people.  A low average life expectancy at birth
means a lot of infants and children dying.  For example, in Mali, the
average life expectancy at birth is between 40 and 50 years of age.  This
does not mean that no one lives to be old -- it means that many infants and
children die.  The average life expectancy at birth in China is lower than
the figure for the US, because they have higher infant and child mortality
rates.  Chinese women who survive childhood are likely to live just as long
as their US counterparts, and have just as much chance of getting breast
cancer due to old age.  The Chinese study compared two groups of older
women, those who had breastfed for two years or longer and those who had
not, and found twice the breast cancer rates in those with the short nursing
careers.

Katherine A. Dettwyler, Ph.D.
Associate Professor of Anthropology and Nutrition
Texas A&M University



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