Lactation and breast carcinoma risk in a South African population.
BACKGROUND
A number of epidemiologic studies have reported a reduced risk of breast carcinoma among women who have lactated but others have not. The current study presents data regarding lactation and breast carcinoma risk from a hospital-based case-control study of black and colored South African women.


METHODS
Incident breast carcinoma cases treated between January 1994 and October 1997 (n = 446) at 2 major hospitals in Cape Town and hospital patients admitted for conditions unrelated to breast carcinoma (controls, n = 1471) were queried regarding the duration of breast-feeding each liveborn child and breast carcinoma risk factors. Multivariate logistic regression models were used to calculate odds ratios (ORs) for various categories of lactation compared with a reference category of never having breast-fed among women who had had at least one full term live birth.


RESULTS
Approximately 83% of cases and 85% of controls had ever breast-fed (OR = 0.9; 95% confidence interval [95% CI], 0.7-1.3). Among all subjects, the ORs for those who lactated for <3 years were near or at unity. Beyond 3 years, ORs extending up to >/=7 years were less than unity, but the 95% CIs included 1.0 (OR for duration of >/=7 years = 0.7; 95% CI, 0.4-1.3). ORs did not vary by menopausal status. Breast carcinoma risk was not found to be related to the duration of breast-feeding the first child, the number of children breast-fed, or the patient's age at first lactation.


CONCLUSIONS
The results of the current study suggest lactation has little or no protective effect on breast carcinoma risk.
Coogan
P F
PF
Slone Epidemiology Unit, Boston University School of Medicine, Brookline, Massachusetts 02446, USA.
Rosenberg
L
L
Shapiro
S
S
Hoffman
M
M
D000367:Age Factors; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics; D002277:Carcinoma / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics; D016022:Case-Control Studies; D003271:Contraceptive Agents, Female / Q000009:adverse effects; D005260:Female; D006801:Humans; D015994:Incidence; D007774:Lactation; D008875:Middle Aged; D016017:Odds Ratio; D010298:Parity; D012306:Risk; D013019:South Africa; D013997:Time Factors
D003271:Contraceptive Agents, Female