Reproductive factors and risk of breast carcinoma in a study of white and African-American women.
BACKGROUND
Few studies have investigated the association between reproductive factors and the risk of breast carcinoma among African-American women. The authors assessed whether the number of full-term pregnancies, age at first full-term pregnancy, and total duration of breastfeeding were associated with similar relative risk estimates in white and African-American women in a large multicenter, population-based case-control study of breast carcinoma.


METHODS
Case patients were 4567 women (2950 white women and 1617 African-American women) ages 35-64 years with newly diagnosed invasive breast carcinoma between 1994 and 1998. Control patients were 4668 women (3012 white women and 1656 African-American women) who were identified by random-digit dialing and were frequency matched to case patients according to study center, race, and age. Adjusted odds ratios and 95% confidence intervals were estimated using unconditional logistic regression.


RESULTS
For white women, the reduction in risk of breast carcinoma per full-term pregnancy was 13% among younger women (ages 35-49 years) and 10% among older women (ages 50-64 years). The corresponding risk reductions for African-American women were 10% and 6%, respectively. Risk decreased significantly with increasing number of full-term pregnancies for both races and both age categories. Duration of lactation was inversely associated with breast carcinoma risk among younger parous white (trend P = 0.0001) and African-American (trend P = 0.01) women. African-American women tended to have more children compared with white women, but parity rates were lower in younger women than in older women in both racial groups. However, breastfeeding was substantially more common in young white women than in young African-American women.


CONCLUSIONS
Overall, parity and lactation had similar effects on breast carcinoma risk in white and African-American women. If younger African-American women now are giving birth to fewer children than in the past, without a substantial increase in breastfeeding, breast carcinoma rates may continue to increase at a more rapid rate among these women compared with white women.
Ursin
Giske
G
Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California 90089, USA. gursin@usc.edu
Bernstein
Leslie
L
Wang
Yaping
Y
Lord
Sarah J
SJ
Deapen
Dennis
D
Liff
Jonathan M
JM
Norman
Sandra A
SA
Weiss
Linda K
LK
Daling
Janet R
JR
Marchbanks
Polly A
PA
Malone
Kathleen E
KE
Folger
Suzanne G
SG
McDonald
Jill A
JA
Burkman
Ronald T
RT
Simon
Michael S
MS
Strom
Brian L
BL
Spirtas
Robert
R
D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data; D001942:Breast Feeding; D001943:Breast Neoplasms / Q000453:epidemiology*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007774:Lactation; D008297:Male; D008423:Maternal Age; D008875:Middle Aged; D010298:Parity; D011159:Population Surveillance; D012306:Risk; D013997:Time Factors; D044465:White People / Q000706:statistics & numerical data