Lactation and breast cancer risk: a case-control study in Connecticut.
In this report, we examined the relationship between lactation and breast cancer risk, in a case-control study of breast cancer, conducted in Connecticut between 1994 and 1998. Included were 608 incident breast cancer cases and 609 age frequency matched controls, aged 30-80 years old. Cases and controls were interviewed by trained study interviewers, using a standardized, structured questionnaire, to obtain information on lactation and other major risk factors. Parous women who reported ever lactation had a borderline significantly reduced risk of breast cancer (OR = 0.83, 95% CI, 0.63-1.09). An OR of 0.53 (95% CI, 0.27-1.04) was observed in those having breastfed more than 3 children compared to those who never lactated. Women having breastfed their first child for more than 13 months had an OR of 0.47 (95% CI, 0.23-0.94) compared to those who never breastfed. Lifetime duration of lactation also showed a risk reduction while none of the ORs were statistically significant. Further stratification by menopausal status showed a risk reduction related to lactation for both pre- and postmenopausal women, while the relationship is less consistent for the latter. These results support an inverse association between breastfeeding and breast cancer risk.
Zheng
T
T
Department of Epidemiology and Public Health, Yale University School of Medicine, 60 College, New Haven, CT 06520, USA.
Holford
T R
TR
Mayne
S T
ST
Owens
P H
PH
Zhang
Y
Y
Zhang
B
B
Boyle
P
P
Zahm
S H
SH
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000209:etiology* / Q000517:prevention & control; D016022:Case-Control Studies; D003237:Connecticut / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D007774:Lactation; D008875:Middle Aged; D016017:Odds Ratio; D018570:Risk Assessment; D013997:Time Factors