This was reported in Lancet in 2002. A good
adjunct to the current information on HRT.
Pat Gima
____________________________________________________________________________________________--
THE LANDMARK STUDY, published this week in The
Lancet medical journal, found that if women in
the industrialized world breast-fed each of their
children six months longer, they could reduce
their chance of breast cancer by 5 percent, even
if they have a strong family history of the disease.
Experts said the findings help explain
the discrepancy between low rates of breast
cancer in developing countries and the rising
number of cases in wealthier nations.
“In the developed world there have been
enormous changes over the last 100 years in
childbearing patterns and this illustrates that
those changes can explain a great deal of the
increase in breast cancer rates,” said Eugina
Calle, director of analytic epidemiology at the American Cancer Society.
The study involved 200 researchers across
the globe examining more than 47 studies that
investigated a total of 150,000 women worldwide.
The analysis of the pooled information was
conducted by epidemiologists at Oxford University in England.
NEW EVIDENCE FOR OLD IDEA
The idea that childbearing is linked to
breast cancer dates to 1743, when an Italian
researcher called the disease an occupational
hazard of nuns, attributing their relatively high
rate of breast cancer to their childlessness.
Breast cancer rates really started to
climb at the end of the 19th century, and by the
1950s, it was well established that the number of
children a woman had was a major factor in breast cancer.
In 1970, a study found that the age at
which a woman had her first child was key, but
that neither the number of children she had nor
her breast-feeding habits mattered.
“Since that time, almost every study on
breast cancer has confirmed that finding on age
at first birth, but there’s been a lot of
confusion about whether the number of children
and breast-feeding had an effect on breast
cancer,” said the new study’s leader, Valerie
Beral, head of the Oxford epidemiology unit.
Confusion has remained, particularly
about the role of breast-feeding, because
individual studies have been too small to provide answers, she said.
STUDY DETAILS
The Oxford group started by looking at
20,000 women who had only one child and who had
never breast-fed, and compared them with women
who did not breast-feed but continued to have children.
“The risks go down the more children
you have. Even if they’d never breast-fed, the
risk of breast cancer went down by 7 percent for
every additional child,” Beral said.
The researchers also found that,
regardless of the number of children, the risk of
breast cancer dropped by 4.3 percent for every year the women breast-fed.
“What we have shown is that prolonging
breast-feeding and having more children pushes
down breast cancer rates,” Beral said.
The magnitude of protection was the same
in all women, regardless of other
characteristics, such as ethnic origin, drinking habits and age at menopause.
In the developed world, women have on
average two or three children and breast-feed
each for about two or three months.
And 50 percent of mothers in the United
States, about 25 percent in Europe and about 10
percent in Scandinavia choose not to breast-feed.
A century ago — before oral
contraception, infant formula, improved infant
survival and career opportunities for women —
Western women used to have six or seven children
and breast-feed each for about two years — a
pattern still dominant in many parts of the developing world.
BREAST CANCER DIVIDE
Today, women in the industrialized world
have a 6.3 percent chance of getting breast
cancer by age 70, compared with a 2.7 percent
chance for their counterparts in poor countries.
Part of the reason is that women in poor
countries have children earlier, at about 18 or
19, compared with 23 or 24 in the developed world.
But that couldn’t explain all the
difference in the breast cancer rates.
“People have been struggling to fill
that gap. Things like diet, alcohol ... all these
things have come up in an attempt to explain the
difference,” Beral said. “But, it’s prolonging
breast-feeding and having lots of children that
really pushes breast cancer rates down.
“There are obviously other determinants,
but they are much smaller. Those two factors
account for much of the difference in breast
cancer rates between developed and developing countries,” Beral said.
Beral calculated that if western
reproductive and breast-feeding habits mimicked
those in poor countries, a woman’s breast cancer
risk by the age of 70 would fall from 6.3 per 100 women to about 2.7.
The researchers also calculated what
would happen to breast cancer risk if women still
had only two or three children but breast-fed
each for six months longer than the norm of two
or three months. That would translate to a
maximum breast-feeding time of nine months per baby.
They found that the chances of breast
cancer would decrease from 6.3 percent to 6 percent, a 5 percent drop.
The National Childbirth Trust, which
promotes breast-feeding, said the research
clearly shows the benefits for mothers as well as children.
“We hope that this important finding —
that the longer women breast-feed, the more they
are protected from breast cancer — will encourage
more women to consider breast-feeding their
baby,” said Belinda Phipps, the chief executive of the trust.
The scientists are not sure how
childbirth and breast-feeding reduce breast
cancer risk but they believe the findings could
pave the way for better prevention and treatment methods.
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