History of lactation and breast cancer risk.
A self-administered questionnaire was completed by 1,018 women diagnosed with breast cancer during 1988-1989 identified through the British Columbia Cancer Registry and by 1,025 controls selected at random from the Provincial Voters List. Parous premenopausal women who had never nursed (odds ratio (OR) = 1.3, 95% confidence interval (CI) 0.9-2.0) or who had lactated for 1 month or less (OR = 1.8, 95% CI 1.3-2.5) had an increased risk of breast cancer adjusted for age and parity, compared with women who had breast-fed 2 months or longer. The risk was particularly elevated (OR = 3.0, 95% CI 1.6-5.4) among women who reported having tried to nurse, but who were unsuccessful. Among women who nursed for at least 2 months, there was an indication of decreasing risk with increasing duration of nursing. Among postmenopausal parous women, no relation between lactation history and breast cancer risk was evident.
Yang
C P
CP
Division of Epidemiology, Biometry, and Occupational Oncology, British Columbia Cancer Agency, Vancouver, Canada.
Weiss
N S
NS
Band
P R
PR
Gallagher
R P
RP
White
E
E
Daling
J R
JR
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology*; D016022:Case-Control Studies; D003625:Data Collection; D005260:Female; D006801:Humans; D007774:Lactation; D016015:Logistic Models; D008875:Middle Aged; D017698:Postmenopause; D017697:Premenopause; D012307:Risk Factors