<I don't have the reference handy, but I believe it was the huge nurses'
study that found no link between breastfeeding and breast cancer.
Several
different topics investigated using the nurses have found directly
opposite
results from what studies from other parts of the country have found.>
Kathy,
I think I may have a clue why.
I have been one of the 120,000 participants in the Harvard Nurses Health
Study, answering a 6-page single-space questionnaire every other year
since 1976. I have sent not only my answers, but blood specimens,
toe-nail specimens (for selenium analysis!), detailed information about
my diet, which brands of vitamins, hair dye, margerine, etc. I have used,
and answered an amazing variety of questions and sent in extra personal
notes during that time period.
I was never directly or indirectly asked for any input on what factors
should be studied.
Your post and your known willingness to speak to us of statistics and
research prompted me to look up my folder of copies of questions, my
answers, and the occasional report of findings. I reviewed every page.
Other than being included on the long list of conditions on which we were
to black in a little circle beside if we had been diagnosed with it in
the previous two years, I found few, if any references to breast cancer
on the questionnaires.
In various years, there were some questions about Tamoxiphen, hormone
usage as in contraceptive and hormone replacement, and questions about
whether we had ever had breast implants of various types.
One year, one question asked "To update our records regarding your
lifetime pregnancy history, please mark a bubble corresponding to each
year in which you gave birth. (include both live births and stillbirths
for pregnancies lasting at least 6 months.). . . . . .There is absolutely
no mention of whether or not one has breastfed, or how long, (let alone
whether or not it was exclusive).
In 1988, the question appeared: Regarding YOUR infancy: a)Were you breast
fed? If yes, number of months. b) Your birthweight in pounds c)Were you
full term, 2+ weeks premature, or a twin or triplet?
It appears to me that this study has never even considered as a variable
whether or not a participant has breastfed-AT ALL. I can only speak as
one who never had to answer yes to having had breast cancer. But I
cannot report on any possible follow-up questionnaires that may have been
sent to those who reported they HAD been so diagnosed. (Over the years,
when I reported a positive history of several other health conditions
(eye problems, arthritis), I received separate further inquiries about my
diagnoses, requests for records etc.)
However, NOT to have asked me about my breastfeeding history certainly
indicates to me that they never took it into consideration as a possible
factor as to why I HADN'T had been diagnosed with breast cancer!
In my 1984 cover letter, this statement appeared:
"In recent analyses we compared risk factors for breast cancer in
premenoausal women with those among postmenopausal women, and found NO
IMPORTANT DIFFERENCES. (emphasis mine). Also, we found no overall
relationship between postmenopausal estrogens and risk of breast cancer.*
(References:
1.) A Prospective Cohort Study of Postmenopausal Female Hormone Use and
Risk of Breast Cancer. Am. J. Epidemiol. 1983; 118:416
2.) A Case-control Study of Risk Indicators Among Women With
Premenopausal and Early Postmenopausal Breast Cancer. Cancer 1984; 53:
1020-4.
Although these findings are reassuring, continued data collection is
necessary to observe possible health effects of these preparations over
longer periods of time. . . . . ."
The 1987 letter I received had references on the back regarding "Dietary
Fat and Breast Cancer" and "A Prospective Study of Alcohol Intake and
Risk of Breast Cancer".
The 1996 Newsletter mentions "Prospective study of long-term oral
contraceptive use and risk of breast cancer."
A table on the back of that newsletter was reproduced from an article
published in the June 1996 American Journal of Nursing. It itemized
Breast Cancer, CHD/Stroke, Colon Cancer, and Fractures across the top in
columns. Listed down the side were the factors investigated. Here are
the comments under just the breast cancer column:
Smoking - No relation with current or past smoking.
Oral Contraceptives - Current use increases risk. Past use no
association.
Postmenopausal Current use for more than 5 years increases
Hormones - risk. Progestins added to estrogen therapy
do not reduce risk.
Obesity - Weak relation with incidence among
postmenopausal women
Alcohol - Two or more drinks per day increases
risk.
Diet - Low vitamin A intake associated with
increased risk, but no
relation for Vitamin C
or E. No relation for total fat
intake.
Monounsaturated fat intake
inversely related
to risk of breast cancer. No
relation with
selenium.
Other exposures - Atypical hyperplasia associated with
increased risk. Family history
accounts for
6% of breast cancer. Use of hair
dyes not
related to risk. First pregnancy
increases risk of breast
cancer (short term). Closer
spacing of births associated with
lower risk.
PERIOD. ABSOLUTELY NO MENTION OF BREASTFEEDING AS A RISK FACTOR EITHER
WAY.
I guess as both a participant and an LC, I ought to make up for lost time
and send them a letter asking how they can make valid breast cancer
research studies without some consideration of this factor.
K. Jean Cotterman RNC, IBCLC
Dayton, Ohio USA
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