TY - JOUR
T1 - Being breastfed in infancy and adult breast cancer risk among Japanese women
AU - Minami, Yuko
AU - Nishino, Yoshikazu
AU - Kawai, Masaaki
AU - Kakugawa, Yoichiro
N1 - Funding Information:
Acknowledgments The authors are grateful to all staff members of the Miyagi Cancer Center who generously cooperated in this study. This work was supported by a grant for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology, Japan (H23-Kiban B-23390169).
PY - 2012/2
Y1 - 2012/2
N2 - Objective: Being breastfed in infancy has been hypothesized to influence subsequent breast cancer risk. In a hospital-based case-control study, we investigated the relationship between having been breastfed and breast cancer risk, both overall and separately among female subjects with different birth years. Methods: The study subjects included 571 cases and 2,155 controls admitted to a single hospital in Miyagi Prefecture, Japan, between 1997 and 2005. History of having been breastfed was assessed with a self-administered questionnaire. Odds ratios (ORs) and 95% confidence interval (CI) were estimated using logistic regression. Results: After adjustment for known risk factors, no association for having been breastfed was observed overall (OR = 1.20; 95% CI: 0.82-1.76). Analysis stratified according to birth year (<1950, ≥1950) demonstrated heterogeneity in the association for having been breastfed between the two birth-year groups (p for interaction = 0.0006); having been breastfed was significantly associated with a decreased risk among subjects who were born before 1950 (OR = 0.59; 95% CI: 0.35-0.99), whereas no such risk reduction was observed for subjects born after 1950 (OR = 1.60; 95% CI: 0.88-2.90). Conclusion: Although having been breastfed is not related to overall risk, birth year may modify the association between having been breastfed in infancy and breast cancer risk. In Japan, sociodemographic changes have occurred since the end of World War II. The use of standard formula supplement began to spread around 1950. The difference of breast cancer risk between birth-year groups may be attributable to these environmental changes.
AB - Objective: Being breastfed in infancy has been hypothesized to influence subsequent breast cancer risk. In a hospital-based case-control study, we investigated the relationship between having been breastfed and breast cancer risk, both overall and separately among female subjects with different birth years. Methods: The study subjects included 571 cases and 2,155 controls admitted to a single hospital in Miyagi Prefecture, Japan, between 1997 and 2005. History of having been breastfed was assessed with a self-administered questionnaire. Odds ratios (ORs) and 95% confidence interval (CI) were estimated using logistic regression. Results: After adjustment for known risk factors, no association for having been breastfed was observed overall (OR = 1.20; 95% CI: 0.82-1.76). Analysis stratified according to birth year (<1950, ≥1950) demonstrated heterogeneity in the association for having been breastfed between the two birth-year groups (p for interaction = 0.0006); having been breastfed was significantly associated with a decreased risk among subjects who were born before 1950 (OR = 0.59; 95% CI: 0.35-0.99), whereas no such risk reduction was observed for subjects born after 1950 (OR = 1.60; 95% CI: 0.88-2.90). Conclusion: Although having been breastfed is not related to overall risk, birth year may modify the association between having been breastfed in infancy and breast cancer risk. In Japan, sociodemographic changes have occurred since the end of World War II. The use of standard formula supplement began to spread around 1950. The difference of breast cancer risk between birth-year groups may be attributable to these environmental changes.
KW - Birth year
KW - Breast cancer
KW - Breast milk
KW - Breast-feeding
KW - Case-control study
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U2 - 10.1007/s10552-011-9888-3
DO - 10.1007/s10552-011-9888-3
M3 - Article
C2 - 22205179
AN - SCOPUS:84856720954
VL - 23
SP - 389
EP - 398
JO - Cancer Causes and Control
JF - Cancer Causes and Control
SN - 0957-5243
IS - 2
ER -